{"id":10913,"date":"2026-09-26T21:56:56","date_gmt":"2026-09-26T20:56:56","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/infrared-spectroscopy\/"},"modified":"2026-10-04T23:03:54","modified_gmt":"2026-10-04T22:03:54","slug":"infrared-spectroscopy","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/infrared-spectroscopy\/","title":{"rendered":"Infrared Spectroscopy"},"content":{"rendered":"<script src=\"https:\/\/cdnjs.cloudflare.com\/ajax\/libs\/three.js\/r128\/three.min.js\"><\/script>\n\n<section class=\"ols-revision-page ols-alcohols-halogenoalkanes-spectra-page\">\n  <style>\n    .ols-revision-page {\n      --navy: #1C244B;\n      --blue: #2563eb;\n      --soft-blue: #eef4ff;\n      --soft-red: #fff7f7;\n      --soft-purple: #f7f0ff;\n      --soft-green: #f0f7f1;\n      --gold: #c9973a;\n      --grey-text: #667085;\n      --body-text: #1f2937;\n      --border: rgba(28, 36, 75, 0.14);\n      --shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      --inner-shadow: 0 10px 26px rgba(28, 36, 75, 0.08);\n      font-family: Poppins, Arial, sans-serif;\n      color: var(--navy);\n      background: #ffffff;\n    }\n    .ols-revision-page * { box-sizing: border-box; }\n\n    .ols-breadcrumbs { display: flex; flex-wrap: wrap; gap: 8px; margin: 10px 0 22px; font-size: 15px; color: var(--grey-text); }\n    .ols-breadcrumbs a, .ols-breadcrumbs span { color: var(--grey-text); text-decoration: none; font-weight: 600; }\n    .ols-breadcrumbs a { transition: color 0.2s ease, text-decoration-color 0.2s ease; }\n    .ols-breadcrumbs a:hover { color: var(--blue); text-decoration: underline; text-underline-offset: 3px; }\n    .ols-title-card, .ols-note-card, .ols-h5p-card, .ols-related-card { background: #ffffff; border: 1px solid var(--border); border-radius: 28px; box-shadow: var(--shadow); padding: 34px; margin-bottom: 24px; overflow: hidden; }\n    .ols-title-card { background: linear-gradient(135deg, #ffffff 0%, #f8fbff 100%); }\n    .ols-title-card h1 { margin: 0 0 18px; font-size: clamp(36px, 5vw, 58px); line-height: 1.08; font-weight: 800; letter-spacing: -0.04em; color: #111827; }\n    .ols-page-intro { font-size: 19px; line-height: 1.7; font-weight: 300; color: var(--body-text); margin: 0 0 22px; }\n    .ols-badges { display: flex; flex-wrap: wrap; gap: 12px; margin-bottom: 22px; }\n    .ols-badge { display: inline-flex; align-items: center; padding: 9px 14px; border-radius: 999px; background: #ffffff; border: 1px solid var(--border); font-size: 15px; font-weight: 600; color: var(--navy); }\n    .ols-note-card.soft { background: linear-gradient(135deg, #ffffff 0%, var(--soft-red) 100%); }\n    .ols-note-card.purple { background: linear-gradient(135deg, #ffffff 0%, var(--soft-purple) 100%); }\n    .ols-note-title { display: flex; align-items: center; gap: 14px; margin-bottom: 20px; }\n    .ols-note-icon { width: 52px; height: 52px; border-radius: 16px; background: var(--navy); color: #ffffff; display: grid; place-items: center; font-size: 24px; font-weight: 800; flex-shrink: 0; }\n    .ols-note-title h2, .ols-h5p-card h2, .ols-related-card h2 { margin: 0; font-size: clamp(28px, 3.5vw, 42px); line-height: 1.15; font-weight: 800; color: #111827; letter-spacing: -0.03em; }\n    .ols-note-card p, .ols-note-card li, .ols-h5p-card p, .ols-related-card p { font-size: clamp(15px, 1.25vw, 17px); line-height: 1.65; font-weight: 300; color: var(--body-text); }\n    .ols-note-card strong, .ols-h5p-card strong, .ols-related-card strong, .ols-faq-card strong { font-weight: 750; color: var(--navy); }\n    .ols-note-card ul { margin: 0; padding-left: 22px; }\n    .ols-key-box { margin-top: 20px; background: var(--soft-green); border: 1px solid rgba(63, 143, 70, 0.25); border-radius: 20px; padding: 18px 20px; }\n    .ols-key-box p { margin: 0; font-weight: 400; color: var(--navy); }\n    .ols-figure-card { margin: 26px 0 4px; border: 1px solid var(--border); border-radius: 26px; overflow: hidden; background: #ffffff; box-shadow: var(--inner-shadow); }\n    .ols-figure-image { width: 100%; min-height: 390px; background-color: #ffffff; background-image: var(--ols-image); background-repeat: no-repeat; background-position: center; background-size: contain; border-bottom: 1px solid var(--border); }\n    .ols-figure-caption { padding: 22px 26px 24px; background: linear-gradient(135deg, #ffffff, #f8fbff); }\n    .ols-figure-caption h3 { margin: 0 0 8px; color: var(--navy); font-size: clamp(21px, 2vw, 30px); line-height: 1.25; font-weight: 800; font-style: italic; }\n    .ols-figure-caption p { margin: 0; color: #5f6b85; font-size: clamp(16px, 1.4vw, 19px); line-height: 1.65; font-weight: 300; font-style: italic; }\n    .ols-table-wrap { overflow-x: auto; border-radius: 22px; border: 1px solid var(--border); background: #ffffff; margin-top: 18px; }\n    .ols-table { width: 100%; border-collapse: collapse; min-width: 680px; }\n    .ols-table th { background: var(--navy); color: #ffffff; padding: 14px 16px; text-align: left; font-size: 15px; font-weight: 700; }\n    .ols-table td { padding: 14px 16px; border-bottom: 1px solid var(--border); font-size: 15px; color: var(--body-text); vertical-align: top; }\n    .ols-table tr:last-child td { border-bottom: none; }\n    .ols-definition-box { background: linear-gradient(135deg, #ffffff, var(--soft-purple)); border: 2px dashed rgba(122, 62, 157, 0.35); border-radius: 24px; padding: 26px; margin-top: 22px; display: grid; grid-template-columns: 1fr; gap: 16px; align-items: center; }\n    .ols-definition-circle { width: 105px; height: 105px; border-radius: 50%; background: linear-gradient(135deg, #9b59b6, #6f3d96); color: white; display: grid; place-items: center; font-size: 28px; font-weight: 800; text-align: center; margin: 0 auto; }\n    .ols-h5p-card { background: linear-gradient(135deg, #ffffff 0%, #f7f0ff 100%); }\n    .ols-h5p-frame { margin-top: 22px; padding: 18px; border-radius: 24px; background: #ffffff; border: 1px solid var(--border); box-shadow: inset 0 0 0 1px rgba(28, 36, 75, 0.03); }\n    .ols-infographic-full { width: 100%; margin: 6px 0 30px; }\n    .ols-infographic-full-frame { width: 100%; border-radius: 22px; overflow: hidden; box-shadow: 0 18px 42px rgba(28, 36, 75, 0.13); background: #ffffff; }\n    .ols-infographic-full-frame img { width: 100%; height: auto; display: block; }\n    .ols-related-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; margin-top: 18px; }\n    .ols-related-item { border: 1px solid var(--border); border-radius: 18px; padding: 18px; background: #ffffff; color: var(--navy); text-decoration: none; font-weight: 600; line-height: 1.5; transition: transform 0.2s ease, box-shadow 0.2s ease; }\n    .ols-related-item:hover { transform: translateY(-2px); box-shadow: 0 10px 22px rgba(28, 36, 75, 0.08); }\n    .ols-unlock { background: linear-gradient(135deg, var(--navy), #0f4fa8); border-radius: 30px; padding: 36px; color: #ffffff; box-shadow: var(--shadow); text-align: center; margin: 30px 0 24px; }\n    .ols-unlock h2 { margin: 0 0 12px; font-size: clamp(30px, 4vw, 46px); line-height: 1.15; font-weight: 800; color: #ffffff; text-align: center; }\n    .ols-unlock p { margin: 0 auto 24px; max-width: 700px; font-size: 20px; line-height: 1.6; font-weight: 300; text-align: center; color: #ffffff; }\n    .ols-cta-button { display: inline-flex; align-items: center; justify-content: center; padding: 14px 26px; border-radius: 999px; background: #ffffff; color: var(--navy); text-decoration: none; font-weight: 700; }\n\n    @media (max-width: 1050px) {\n      .ols-main { max-width: none; }\n      .ols-related-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }\n    }\n\n    @media (max-width: 760px) {\n      .ols-title-card, .ols-note-card, .ols-h5p-card, .ols-related-card, .ols-unlock { padding: 24px 18px; border-radius: 22px; }\n      .ols-note-title { align-items: flex-start; }\n      .ols-figure-card { border-radius: 22px; }\n      .ols-figure-image { min-height: 250px; }\n      .ols-figure-caption { padding: 18px; }\n      .ols-topic-list, .ols-related-grid { grid-template-columns: 1fr; }\n      .ols-infographic-full { margin: 0 0 26px; }\n      .ols-infographic-full-frame { border-radius: 18px; }\n    }\n    .ols-author {\n      display: flex;\n      align-items: center;\n      gap: 20px;\n      padding: 28px;\n      border-radius: 28px;\n      background: linear-gradient(135deg, #ffffff 0%, #f8fbff 100%);\n      border: 1px solid rgba(28, 36, 75, 0.12);\n      box-shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      margin-top: 22px;\n    }\n    .ols-author-avatar-img {\n      width: 92px;\n      height: 92px;\n      border-radius: 50%;\n      object-fit: cover;\n      object-position: center;\n      flex-shrink: 0;\n      border: 4px solid #ffffff;\n      box-shadow: 0 14px 32px rgba(28, 36, 75, 0.18), 0 0 0 1px rgba(28, 36, 75, 0.10);\n      transition: transform 0.25s ease, box-shadow 0.25s ease;\n    }\n    .ols-author:hover .ols-author-avatar-img {\n      transform: scale(1.04);\n      box-shadow: 0 20px 42px rgba(28, 36, 75, 0.22), 0 0 0 1px rgba(28, 36, 75, 0.10);\n    }\n    .ols-author-content { min-width: 0; }\n    .ols-author-title {\n      margin: 0 0 4px;\n      font-size: clamp(24px, 3vw, 34px);\n      line-height: 1.15;\n      font-weight: 700;\n      color: var(--navy);\n      letter-spacing: -0.03em;\n    }\n    .ols-author-description {\n      margin: 0;\n      font-size: 17px;\n      line-height: 1.7;\n      font-weight: 300;\n      color: var(--grey-text);\n    }\n    .ols-linkedin-pill {\n      display: inline-flex;\n      align-items: center;\n      justify-content: center;\n      gap: 10px;\n      margin-top: 16px;\n      padding: 11px 18px;\n      border-radius: 999px;\n      background: linear-gradient(135deg, #0A66C2, #004182);\n      color: #ffffff;\n      text-decoration: none;\n      font-size: 14px;\n      line-height: 1;\n      font-weight: 700;\n      letter-spacing: 0.01em;\n      box-shadow: 0 10px 22px rgba(10, 102, 194, 0.24);\n      position: relative;\n      overflow: hidden;\n      transition: transform 0.22s ease, box-shadow 0.22s ease;\n    }\n    .ols-linkedin-pill:hover {\n      transform: translateY(-3px) scale(1.03);\n      box-shadow: 0 16px 34px rgba(10, 102, 194, 0.34), 0 0 0 6px rgba(10, 102, 194, 0.10);\n    }\n    .ols-linkedin-icon { width: 18px; height: 18px; display: block; flex-shrink: 0; }\n    .ols-attribution-card {\n      background: linear-gradient(135deg, #ffffff, #f8fbff);\n      border: 1px solid rgba(28, 36, 75, 0.14);\n      border-radius: 28px;\n      box-shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      padding: 34px;\n      margin-bottom: 24px;\n      overflow: hidden;\n      box-sizing: border-box;\n    }\n    .ols-attribution-card p {\n      margin: 0;\n      font-size: 14px;\n      line-height: 1.65;\n      font-weight: 300;\n      color: #667085;\n    }\n    .ols-attribution-card strong { font-weight: 700; color: #1C244B; }\n      .ols-note-card h3 { margin: 22px 0 8px; font-size: 18px; line-height: 1.25; font-weight: 500; color: var(--navy); }\n  \n    .ols-figure-placeholder .ols-placeholder-box { border: 2px dashed #c9973a; background: #fffaf0; border-radius: 16px; padding: 26px 22px; font-weight: 700; color: #7a4b12; text-align: center; line-height: 1.6; }\n    .ols-figure-placeholder .ols-figure-image { background: transparent; }\n    .ols-figure-placeholder { background: #ffffff; border: 1px solid rgba(28, 36, 75, 0.12); border-radius: 22px; padding: 14px; margin: 18px 0 6px; }\n    .ols-figure-placeholder .ols-figure-caption p { margin: 10px 0 0; font-size: 14px; color: #667085; text-align: center; }\n\n    \/* inline checks (H5P re-flow, Sep 2026) *\/\n    .ols-h5p-card.ols-h5p-inline { padding: 26px 28px; border-left: 6px solid #7c3aed; }\n    .ols-h5p-card.ols-h5p-inline h2 { font-size: clamp(20px, 2.2vw, 27px); letter-spacing: -0.02em; }\n    .ols-h5p-card.ols-h5p-inline > p { margin: 8px 0 0; }\n    .ols-h5p-card.ols-h5p-inline .ols-h5p-frame { margin-top: 16px; padding: 14px; border-radius: 20px; }\n    .ols-h5p-kicker { display: inline-block; margin-bottom: 10px; padding: 5px 12px; border-radius: 999px; background: #ede9fe; color: #5b21b6; font-size: 12px; font-weight: 700; letter-spacing: 0.06em; text-transform: uppercase; }\n    .ols-h5p-card.ols-h5p-recap { border-left-color: #c9973a; background: linear-gradient(135deg, #ffffff 0%, #fff8e8 100%); }\n    .ols-h5p-recap .ols-h5p-kicker { background: #fdf0d2; color: #8a5a00; }\n    @media (max-width: 760px) { .ols-h5p-card.ols-h5p-inline { padding: 20px 16px; } }\n\n.ols-faq-card,\n    .ols-quicksnap-card {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 28px;\n      box-shadow: var(--shadow);\n      padding: 34px;\n      margin-bottom: 24px;\n      overflow: hidden;\n    }\n.ols-faq-card h2,\n    .ols-quicksnap-card h2,\n    .ols-infographic-title {\n      margin: 0;\n      font-size: clamp(28px, 3.5vw, 42px);\n      line-height: 1.15;\n      font-weight: 800;\n      color: #111827;\n      letter-spacing: -0.03em;\n    }\n.ols-faq-card h2,\n    .ols-quicksnap-card h2 {\n      margin-bottom: 14px;\n    }\n.ols-faq-card p,\n    .ols-quicksnap-card p {\n      font-size: clamp(15px, 1.25vw, 17px);\n      line-height: 1.65;\n      font-weight: 300;\n      color: var(--body-text);\n    }\n.ols-faq-card strong,\n    .ols-quicksnap-card strong {\n      font-weight: 700;\n      color: var(--navy);\n    }\n.ols-faq-list {\n      display: grid;\n      gap: 14px;\n      margin-top: 18px;\n    }\n.ols-faq-item {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 18px 20px;\n      box-shadow: var(--inner-shadow);\n    }\n.ols-faq-item h3 {\n      margin: 0 0 8px;\n      font-size: 20px;\n      line-height: 1.3;\n      color: var(--navy);\n    }\n.ols-faq-item p {\n      margin: 0;\n      font-size: 16px;\n      line-height: 1.65;\n      color: var(--body-text);\n    }\n.ols-faq-card,\n      .ols-quicksnap-card,\n      .ols-attribution-card {\n        padding: 24px 18px;\n        border-radius: 22px;\n      }\n  <\/style>\n\n    <aside class=\"ols-sidebar\">\n  <div class=\"ols-sidebar-header\">\n    <h3>Revision Notes<\/h3>\n    <p>A Level Chemistry<\/p>\n  <\/div>\n\n  <div class=\"ols-topic-group\">\n    <h4>Topic 10 Alcohols, Halogenoalkanes &amp; Spectra<\/h4>\n\n    <ul class=\"ols-topic-list\">\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/\">Topic 10 Overview<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10a-alcohols\/\">Topic 10A Alcohols<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10a-alcohols\/alcohols-naming-classification-and-properties\/\">Alcohols: Naming, Classification and Properties<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10a-alcohols\/oxidation-of-alcohols\/\">Oxidation of Alcohols<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10a-alcohols\/reactions-of-alcohols\/\">Substitution and Elimination Reactions of Alcohols<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10a-alcohols\/preparing-and-purifying-organic-liquids\/\">Preparing and Purifying Organic Liquids<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-6-chlorination-of-2-methylpropan-2-ol\/\">Core Practical 6<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-7-oxidation-of-propan-1-ol\/\">Core Practical 7<\/a>\n          <\/li>\n        <\/ul>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10b-halogenoalkanes\/\">Topic 10B Halogenoalkanes<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10b-halogenoalkanes\/reaction-types-mechanisms-and-nucleophiles\/\">Reaction Types, Mechanisms and Nucleophiles<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10b-halogenoalkanes\/halogenoalkanes-naming-classification-and-bonding\/\">Halogenoalkanes: Naming, Classification and the C\u2013X Bond<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10b-halogenoalkanes\/nucleophilic-substitution-reactions\/\">Nucleophilic Substitution Reactions<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10b-halogenoalkanes\/elimination-reactions-of-halogenoalkanes\/\">Elimination Reactions of Halogenoalkanes<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10b-halogenoalkanes\/rates-of-hydrolysis-and-bond-enthalpy\/\">Rates of Hydrolysis and Bond Enthalpy<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-5-hydrolysis-of-halogenoalkanes\/\">Core Practical 5<\/a>\n          <\/li>\n        <\/ul>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/\">Topic 10C Spectra<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/mass-spectra-of-organic-compounds\/\">Mass Spectra of Organic Compounds<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/infrared-spectroscopy\/\">Infrared Spectroscopy<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/identifying-unknown-compounds\/\">Identifying Unknown Compounds<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/cp-8-analysis-of-inorganic-and-organic-unknowns\/\">Core Practical 8<\/a>\n          <\/li>\n        <\/ul>\n      <\/li>\n    <\/ul>\n  <\/div>\n\n  <div class=\"ols-topic-group\">\n    <h4>Other Topics<\/h4>\n\n    <ul class=\"ols-topic-list\">\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/\">Topic 4 Organic Chemistry &amp; Alkanes<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-5-alkenes\/\">Topic 5 Alkenes<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-9-kinetics-and-equilibria\/\">Topic 9 Kinetics &amp; Equilibria<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/core-practicals\/\">Core Practicals<\/a>\n      <\/li>\n    <\/ul>\n  <\/div>\n<\/aside>\n\n<script>\r\n(function() {\r\n  function normalisePath(path) {\r\n    return String(path || '')\r\n      .split('?')[0]\r\n      .split('#')[0]\r\n      .replace(\/\\\/+$\/, '')\r\n      .toLowerCase();\r\n  }\r\n\r\n  function highlightActive() {\r\n    var sidebar = document.querySelector('.ols-sidebar');\r\n    if (!sidebar) return false;\r\n\r\n    var currentPath = normalisePath(window.location.pathname);\r\n    var links = sidebar.querySelectorAll('a[href]');\r\n    var matched = null;\r\n    var matchedLength = 0;\r\n\r\n    sidebar.querySelectorAll('.active, .active-main, .parent-active').forEach(function(item) {\r\n      item.classList.remove('active', 'active-main', 'parent-active');\r\n    });\r\n\r\n    sidebar.querySelectorAll('a[data-ols-disabled-parent=\"1\"], a[aria-current]').forEach(function(a) {\r\n      a.removeAttribute('aria-current');\r\n      a.removeAttribute('tabindex');\r\n      a.removeAttribute('data-ols-disabled-parent');\r\n    });\r\n\r\n    links.forEach(function(a) {\r\n      try {\r\n        var href = a.getAttribute('href');\r\n\r\n        if (!href || href === '#' || href.charAt(0) === '#') {\r\n          return;\r\n        }\r\n\r\n        var linkPath = normalisePath(new URL(href, window.location.origin).pathname);\r\n\r\n        if (!linkPath) {\r\n          return;\r\n        }\r\n\r\n        if (currentPath === linkPath || currentPath.indexOf(linkPath + '\/') === 0) {\r\n          if (linkPath.length > matchedLength) {\r\n            matched = a;\r\n            matchedLength = linkPath.length;\r\n          }\r\n        }\r\n      } catch(e) {}\r\n    });\r\n\r\n    if (matched) {\r\n      var matchedLi = matched.closest('li');\r\n      var parentSub = matched.closest('.ols-subtopic-list');\r\n\r\n      if (parentSub) {\r\n        if (matchedLi) {\r\n          matchedLi.classList.add('active');\r\n          matched.setAttribute('aria-current', 'page');\r\n        }\r\n\r\n        var parentLi = parentSub.closest('li');\r\n\r\n        if (parentLi) {\r\n          parentLi.classList.add('parent-active', 'active-main');\r\n\r\n          var parentLink = parentLi.querySelector(':scope > a');\r\n\r\n          if (parentLink) {\r\n            parentLink.setAttribute('aria-current', 'true');\r\n            parentLink.setAttribute('tabindex', '-1');\r\n            parentLink.setAttribute('data-ols-disabled-parent', '1');\r\n          }\r\n        }\r\n      } else {\r\n        if (matchedLi) {\r\n          matchedLi.classList.add('parent-active', 'active-main');\r\n          matched.setAttribute('aria-current', 'page');\r\n          matched.setAttribute('tabindex', '-1');\r\n          matched.setAttribute('data-ols-disabled-parent', '1');\r\n        }\r\n      }\r\n    }\r\n\r\n    return true;\r\n  }\r\n\r\n  if (!highlightActive()) {\r\n    document.addEventListener('DOMContentLoaded', highlightActive);\r\n  }\r\n})();\r\n<\/script>\r\n\n\n    <main class=\"ols-main\">\n\n      <!-- BREADCRUMBS - updated with full path and correct links -->\n      <nav class=\"ols-breadcrumbs\" aria-label=\"Breadcrumb\">\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\">Revision Notes<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\">A Level Chemistry<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">Edexcel International<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/\">Topic 10 Alcohols, Halogenoalkanes and Spectra<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/\">Topic 10C Spectra<\/a> \/\n<span>Infrared Spectroscopy<\/span>\n<\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Infrared Spectroscopy<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to infrared spectroscopy: why bonds absorb infrared radiation, wavenumbers and transmittance, the characteristic absorptions of C\u2013H, C=C, C=O, O\u2013H, N\u2013H and C\u2013X bonds, the fingerprint region.<\/p>\n        <div class=\"ols-badges\">\n<div class=\"ols-badge\">Exam board: Edexcel International<\/div>\n<div class=\"ols-badge\">Unit 2: WCH12\/01<\/div>\n<div class=\"ols-badge\">Topic 10C Spectra<\/div>\n<\/div>\n        <div class=\"ols-author\">\n\n    <img decoding=\"async\"\n      class=\"ols-author-avatar-img\"\n      src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\"\n      alt=\"Dr. Mohammed Al-Fatah\"\n    >\n\n    <div class=\"ols-author-content\">\n\n      <h2 class=\"ols-author-title\">\n        Written by: Dr. Mohammed Al-Fatah\n      <\/h2>\n\n      <p class=\"ols-author-description\">\n        Chemistry specialist revision notes for A Level Chemistry.\n      <\/p>\n\n      <a class=\"ols-linkedin-pill\" href=\"https:\/\/www.linkedin.com\/in\/doctormohammedfatah\/\" target=\"_blank\" rel=\"noopener noreferrer\">\n        <svg class=\"ols-linkedin-icon\" viewBox=\"0 0 24 24\" fill=\"currentColor\" aria-hidden=\"true\">\n          <path d=\"M4.98 3.5C4.98 4.88 3.86 6 2.48 6S0 4.88 0 3.5 1.12 1 2.48 1s2.5 1.12 2.5 2.5zM.5 8h4V24h-4V8zm7 0h3.8v2.2h.1c.5-.9 1.8-2.2 3.9-2.2 4.2 0 5 2.8 5 6.4V24h-4v-7.6c0-1.8 0-4.2-2.6-4.2s-3 2-3 4v7.8h-4V8z\"\/>\n        <\/svg>\n        View LinkedIn Profile\n      <\/a>\n\n    <\/div>\n\n  <\/div>\n      <\/header>\n\n      <section class=\"ols-h5p-card ols-h5p-inline ols-h5p-recap\">\n<span class=\"ols-h5p-kicker\">Before you start<\/span>\n<h2>GCSE Recap: Bonds and Energy<\/h2>\n<p>Three quick questions on covalent bonds, the electromagnetic spectrum and why greenhouse gases warm the atmosphere.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"970\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">1<\/div>\n<h2>Why Bonds Absorb Infrared<\/h2>\n<\/div>\n<p>The atoms joined by a covalent bond are always vibrating: the bond stretches and compresses, and the angles between bonds bend.<\/p><p>Each vibration has its own natural frequency, which depends on the masses of the atoms and the strength of the bond.<\/p><p>When <strong>infrared radiation<\/strong> of that same frequency passes through the sample, the bond absorbs it and vibrates more energetically. An infrared spectrometer records which frequencies are absorbed, so the spectrum shows which bonds are present.<\/p>\n<p>The frequency is given as a <strong>wavenumber<\/strong> in cm\u207b\u00b9 (the number of waves per centimetre), plotted from about 4000 on the left to 500 on the right.<\/p><p>The y-axis is <strong>transmittance<\/strong>, the percentage of the radiation that passes through, so an absorption appears as a <strong>trough<\/strong> pointing downwards.<\/p><p>Stronger bonds and lighter atoms vibrate faster and absorb at higher wavenumbers: O\u2013H and N\u2013H absorb near 3300 cm\u207b\u00b9, C=O near 1700 cm\u207b\u00b9, and C\u2013Cl near 700 cm\u207b\u00b9.<\/p>\n<!-- 3D card: infrared-bonds (26 Sep 2026) -->\n<!-- Copyright (c) 2026 Dr. Mohammed Al-Fatah, onlinelearningsystem.net. All rights reserved. -->\n<section class=\"ols-irs-001\" id=\"olsIrs001\">\n<style>\n@import url('https:\/\/fonts.googleapis.com\/css2?family=Poppins:wght@300;400;500;600&display=swap');\n\n.ols-irs-001{\n  font-family:'Poppins',system-ui,-apple-system,'Segoe UI',Roboto,Helvetica,Arial,sans-serif;\n  color:#1C244B; background:#ffffff;\n  border:1px solid rgba(28,36,75,0.14);\n  border-radius:28px;\n  box-shadow:0 18px 45px rgba(28,36,75,0.10);\n  padding:44px; margin:26px auto; max-width:980px;\n  box-sizing:border-box; -webkit-font-smoothing:antialiased;\n}\n.ols-irs-001 *{box-sizing:border-box;}\n\n.ols-irs-001 .irs-head{margin:0 0 22px;}\n.ols-irs-001 h2.irs-title{\n  font-size:26px; line-height:1.25; font-weight:600; letter-spacing:-0.012em;\n  margin:0 0 9px; color:#1C244B;\n}\n.ols-irs-001 p.irs-sub{\n  font-size:14.5px; line-height:1.62; font-weight:300; color:#4a5270;\n  margin:0; max-width:66ch;\n}\n\n.ols-irs-001 .irs-stage{\n  position:relative; width:100%; height:560px;\n  background:#ffffff; border:1px solid rgba(28,36,75,0.12);\n  border-radius:18px; overflow:hidden;\n}\n.ols-irs-001 .irs-canvas{\n  display:block; width:100%; height:100%;\n  touch-action:none; cursor:grab; background:#ffffff;\n}\n.ols-irs-001 .irs-canvas.is-drag{cursor:grabbing;}\n.ols-irs-001 .irs-overlay{position:absolute; inset:0; pointer-events:none; overflow:hidden;}\n\n.ols-irs-001 .irs-lab{\n  position:absolute; left:0; top:0; transform:translate(-50%,-50%);\n  white-space:nowrap; font-size:12.5px; font-weight:500; line-height:1;\n  padding:5px 10px; background:rgba(255,255,255,0.93);\n  border:1px solid rgba(28,36,75,0.16); border-radius:999px;\n  color:#1C244B; will-change:transform;\n}\n.ols-irs-001 .irs-lab.l-dom{border-color:rgba(59,120,220,0.55); color:#1d4fb0;}\n.ols-irs-001 .irs-lab.l-mol{border-color:rgba(28,36,75,0.32); color:#1C244B;}\n.ols-irs-001 .irs-lab.l-bd{font-size:11.5px; font-weight:600; padding:3px 8px; border-color:rgba(28,36,75,0.28); color:#1C244B;}\n.ols-irs-001 .irs-lab.l-sel{font-size:12px; font-weight:700; padding:3px 9px; border-color:rgba(20,160,160,0.8); color:#0e6f6b; background:#ffffff;}\n.ols-irs-001 .r-teal b{color:#0e6f6b;}\n.ols-irs-001 .irs-canvas.is-pick{cursor:pointer;}\n.ols-irs-001 .irs-lab.l-dp{font-size:15px; font-weight:700; padding:3px 9px; border-color:rgba(37,99,235,0.55); color:#1d47b8;}\n.ols-irs-001 .irs-lab.l-dm{font-size:15px; font-weight:700; padding:3px 9px; border-color:rgba(192,53,45,0.55); color:#a8281f;}\n.ols-irs-001 .irs-lab.l-lp{font-size:11.5px; font-weight:600; border-color:rgba(59,120,220,0.55); color:#1d4fb0;}\n.ols-irs-001 .r-bars{display:grid; grid-template-columns:auto 1fr auto; gap:3px 8px; align-items:center; margin-top:4px; font-size:11px; color:#4a5270;}\n.ols-irs-001 .r-bars i{display:block; height:7px; border-radius:4px; background:#c6cad8;}\n.ols-irs-001 .r-bars .on{font-weight:600; color:#1C244B;}\n.ols-irs-001 .r-bars .on i{background:#c9961c;}\n.ols-irs-001 .irs-lab.l-ion{font-size:13px; font-weight:600; border-color:rgba(28,36,75,0.32); color:#1C244B;}\n.ols-irs-001 .irs-lab.l-prod{font-size:12.5px; font-weight:600; border-color:rgba(201,150,28,0.75); color:#8a6410;}\n.ols-irs-001 .irs-lab.l-rul{font-size:11.5px; font-weight:600; padding:2px 7px; color:#1C244B; border-color:rgba(28,36,75,0.5); background:#ffffff;}\n.ols-irs-001 .irs-lab.l-ang{font-size:13.5px; font-weight:600; border-color:rgba(201,150,28,0.75); color:#8a6410; background:#ffffff;}\n\n.ols-irs-001 .irs-caption .c2{display:block; margin-top:3px; font-weight:600; color:#0e6f6b;}\n.ols-irs-001 .irs-caption{\n  position:absolute; left:14px; top:14px; max-width:60%;\n  font-size:12px; font-weight:500; color:#4a5270; line-height:1.35;\n  background:rgba(255,255,255,0.92); padding:6px 12px;\n  border-radius:14px; border:1px solid rgba(28,36,75,0.12);\n}\n.ols-irs-001 .irs-hint{\n  position:absolute; right:14px; top:14px;\n  font-size:11.5px; font-weight:400; color:#8b92a8;\n  background:rgba(255,255,255,0.9); padding:5px 11px;\n  border-radius:999px; border:1px solid rgba(28,36,75,0.10);\n}\n.ols-irs-001 .irs-badges{\n  position:absolute; right:14px; bottom:14px; max-width:58%;\n  display:flex; flex-direction:column; align-items:flex-end; gap:6px;\n}\n.ols-irs-001 .irs-badge{\n  font-size:12px; font-weight:500; color:#1C244B; line-height:1.35; text-align:right;\n  background:rgba(255,255,255,0.95); padding:5px 12px;\n  border-radius:14px; border:1px solid rgba(28,36,75,0.22);\n}\n.ols-irs-001 .irs-badge.b-eq{font-size:13.5px; font-weight:600; border-color:rgba(201,150,28,0.75);}\n.ols-irs-001 .irs-badge.b-shape{font-size:14px; font-weight:600; border-color:rgba(201,150,28,0.75);}\n.ols-irs-001 .irs-badges.hide{display:none;}\n\n.ols-irs-001 .irs-stack{\n  position:absolute; left:14px; top:52px; max-width:62%;\n  display:flex; flex-direction:column; align-items:flex-start; gap:6px; pointer-events:none;\n}\n.ols-irs-001 .irs-read{\n  display:flex; flex-direction:column; gap:3px;\n  background:rgba(255,255,255,0.94); padding:7px 12px;\n  border-radius:14px; border:1px solid rgba(28,36,75,0.14);\n}\n.ols-irs-001 .r-line{font-size:12.5px; font-weight:500; color:#1C244B; line-height:1.4; white-space:nowrap;}\n.ols-irs-001 .r-line b{font-weight:600;}\n.ols-irs-001 .r-hot b{color:#8a6410;}\n.ols-irs-001 .r-line span{margin-left:8px; font-size:11.5px; font-weight:400; color:#7d8399;}\n.ols-irs-001 .irs-panel{\n  position:absolute; left:50%; bottom:14px; transform:translateX(-50%);\n  font-size:14.5px; font-weight:600; color:#1C244B; white-space:nowrap;\n  background:#ffffff; padding:8px 16px;\n  border-radius:14px; border:1.5px solid rgba(201,150,28,0.8);\n  box-shadow:0 6px 18px rgba(28,36,75,0.08);\n}\n.ols-irs-001 .irs-panel .neg{color:#8a6410;}\n.ols-irs-001 .irs-read.hide,.ols-irs-001 .irs-panel.hide{display:none;}\n\n.ols-irs-001 .irs-controls{margin-top:20px; display:flex; flex-direction:column; gap:12px;}\n.ols-irs-001 .irs-row{display:flex; align-items:center; gap:10px; flex-wrap:wrap;}\n.ols-irs-001 .irs-rowlab{font-size:12px; font-weight:500; color:#6b7290; min-width:100px; flex:0 0 auto;}\n\n.ols-irs-001 .irs-seg{\n  display:inline-flex; border:1px solid rgba(28,36,75,0.16);\n  border-radius:12px; overflow:hidden; background:#fbfbfd; flex-wrap:wrap;\n}\n.ols-irs-001 .irs-seg button{\n  font-family:inherit; font-size:14px; font-weight:500; color:#3c4463;\n  background:transparent; border:0; border-right:1px solid rgba(28,36,75,0.12);\n  padding:9px 18px; cursor:pointer; transition:background .15s, color .15s;\n}\n.ols-irs-001 .irs-seg button:last-child{border-right:0;}\n.ols-irs-001 .irs-seg button:hover{background:rgba(37,99,235,0.06);}\n.ols-irs-001 .irs-seg button[aria-pressed=\"true\"]{background:#2563eb; color:#fff;}\n.ols-irs-001 .irs-seg button:focus-visible{outline:2px solid #2563eb; outline-offset:-2px;}\n\n.ols-irs-001 .irs-pill{\n  font-family:inherit; font-size:13px; font-weight:500; color:#3c4463;\n  background:#fbfbfd; border:1px solid rgba(28,36,75,0.16);\n  border-radius:999px; padding:8px 16px; cursor:pointer;\n  display:inline-flex; align-items:center; gap:8px;\n  transition:background .15s, border-color .15s, color .15s;\n}\n.ols-irs-001 .irs-pill:hover{border-color:rgba(37,99,235,0.4);}\n.ols-irs-001 .irs-pill:focus-visible{outline:2px solid #2563eb; outline-offset:2px;}\n\n.ols-irs-001 .irs-info{\n  margin-top:22px; padding:22px 24px;\n  border:1px solid rgba(28,36,75,0.12); border-radius:16px; background:#fbfbfd;\n}\n.ols-irs-001 .irs-info h3{margin:0 0 8px; font-size:15.5px; font-weight:600; color:#1C244B;}\n.ols-irs-001 .irs-info p{margin:0; font-size:14px; line-height:1.68; font-weight:300; color:#41496a; max-width:74ch;}\n.ols-irs-001 .irs-facts{\n  margin-top:16px; display:flex; gap:26px; flex-wrap:wrap;\n  padding-top:16px; border-top:1px solid rgba(28,36,75,0.10);\n}\n.ols-irs-001 .irs-fact{min-width:110px;}\n.ols-irs-001 .irs-fact span{display:block; font-size:11.5px; color:#7d8399; font-weight:400; margin-bottom:3px;}\n.ols-irs-001 .irs-fact strong{display:block; font-size:15px; font-weight:600; color:#1C244B;}\n\n.ols-irs-001 .irs-key{\n  margin-top:16px; display:flex; gap:20px; flex-wrap:wrap;\n  font-size:12.5px; font-weight:400; color:#5a6180;\n}\n.ols-irs-001 .irs-key i{\n  display:inline-block; width:13px; height:13px; border-radius:3px;\n  margin-right:7px; vertical-align:-2px; border:1px solid rgba(28,36,75,0.18);\n}\n\n.ols-irs-001 .irs-readbar{\n  margin-top:12px; min-height:38px; display:flex; align-items:center; flex-wrap:wrap; gap:4px 10px;\n  padding:8px 14px; border:1px solid rgba(20,160,160,0.35); border-radius:14px; background:#f5fbfb;\n  font-size:14px; color:#1C244B; line-height:1.4;\n}\n.ols-irs-001 .irs-readbar.hide{display:none;}\n.ols-irs-001 .irs-readbar .rb-k{font-size:11.5px; font-weight:600; text-transform:uppercase; letter-spacing:0.04em; color:#0e6f6b;}\n.ols-irs-001 .irs-readbar b{font-weight:600;}\n.ols-irs-001 .irs-readbar .rb-w{font-weight:600; color:#0e6f6b;}\n.ols-irs-001 .irs-readbar .rb-n{color:#6b7290; font-size:13px;}\n.ols-irs-001 .irs-caption{top:auto; bottom:14px;}\n\n@media (max-width:760px){\n  .ols-irs-001{padding:26px; border-radius:22px;}\n  .ols-irs-001 h2.irs-title{font-size:20.5px;}\n  .ols-irs-001 p.irs-sub{font-size:13.5px;}\n  .ols-irs-001 .irs-stage{height:540px;}\n  .ols-irs-001 .irs-readbar{font-size:12.5px; padding:7px 11px;}\n  .ols-irs-001 .irs-caption{max-width:none;}\n  .ols-irs-001 .irs-rowlab{min-width:100%;}\n  .ols-irs-001 .irs-seg button{padding:9px 13px; font-size:13px;}\n  .ols-irs-001 .irs-lab{font-size:10.5px; padding:4px 8px;}\n  .ols-irs-001 .irs-caption{font-size:10.5px; padding:5px 9px; max-width:64%;}\n  .ols-irs-001 .irs-badge{font-size:10.5px; padding:4px 9px;}\n  .ols-irs-001 .irs-badge.b-shape{font-size:12px;}\n  .ols-irs-001 .irs-badges{max-width:62%;}\n  .ols-irs-001 .irs-info{padding:18px;}\n  .ols-irs-001 .irs-stack{top:auto; bottom:auto; top:48px; max-width:72%;}\n  .ols-irs-001 .r-line{font-size:10.5px;}\n  .ols-irs-001 .r-line{white-space:normal;}\n  .ols-irs-001 .irs-lab.l-bd,.ols-irs-001 .irs-lab.l-sel{font-size:9.5px; padding:2px 6px;}\n  .ols-irs-001 .irs-lab.l-dp,.ols-irs-001 .irs-lab.l-dm{font-size:12px;}\n  .ols-irs-001 .r-bars{font-size:9.5px;}\n  .ols-irs-001 .irs-lab.l-ion,.ols-irs-001 .irs-lab.l-prod{font-size:10.5px;}\n  .ols-irs-001 .irs-lab.l-rul{font-size:9.5px; padding:1px 5px;}\n  .ols-irs-001 .irs-badge.b-eq{font-size:11px;}\n  .ols-irs-001 .irs-read{padding:5px 9px;}\n  .ols-irs-001 .irs-panel{left:auto; right:14px; transform:none; font-size:11px; padding:6px 10px;}\n}\n@media (prefers-reduced-motion:reduce){\n  .ols-irs-001 .irs-seg button,.ols-irs-001 .irs-pill{transition:none;}\n}\n\n.ols-cc-irs-001{\n  font-family:'Poppins',system-ui,-apple-system,'Segoe UI',Roboto,Helvetica,Arial,sans-serif;\n  margin:10px auto 0; text-align:center; font-size:11px; font-style:italic; color:#aab0c0;\n}\n.ols-cc-irs-001 a{color:#aab0c0; text-decoration:none;}\n.ols-cc-irs-001 a:hover{text-decoration:underline;}\n<\/style>\n\n<div class=\"irs-head\">\n  <h2 class=\"irs-title\">Infrared Spectroscopy: Bonds That Vibrate<\/h2>\n  <p class=\"irs-sub\">Choose a molecule: each bond stretches in turn, then the molecule bends, and the matching trough lights up on its infrared spectrum.<\/p>\n<\/div>\n\n<div class=\"irs-stage\" id=\"irsStage\">\n  <canvas class=\"irs-canvas\" id=\"irsCanvas\"><\/canvas>\n  <div class=\"irs-overlay\" id=\"irsOverlay\"><\/div>\n  <div class=\"irs-caption\" id=\"irsCaption\"><\/div>\n  <div class=\"irs-hint\" id=\"irsHint\">Drag to rotate<\/div>\n  <div class=\"irs-badges\" id=\"irsBadges\"><\/div>\n<\/div>\n\n<div class=\"irs-readbar hide\" id=\"irsRead\" aria-live=\"polite\"><\/div>\n\n<div class=\"irs-controls\">\n  <div class=\"irs-row\">\n    <span class=\"irs-rowlab\">Molecule<\/span>\n    <div class=\"irs-seg\" role=\"group\" aria-label=\"Molecule\" id=\"irsMols\">\n      <button type=\"button\" data-m=\"ethanol\" aria-pressed=\"true\">Ethanol CH<sub>3<\/sub>CH<sub>2<\/sub>OH<\/button>\n      <button type=\"button\" data-m=\"ethanal\" aria-pressed=\"false\">Ethanal CH<sub>3<\/sub>CHO<\/button>\n      <button type=\"button\" data-m=\"acid\" aria-pressed=\"false\">Ethanoic acid CH<sub>3<\/sub>COOH<\/button>\n      <button type=\"button\" data-m=\"chloro\" aria-pressed=\"false\">Chloroethane CH<sub>3<\/sub>CH<sub>2<\/sub>Cl<\/button>\n      <button type=\"button\" data-m=\"green\" aria-pressed=\"false\">Greenhouse gases CO<sub>2<\/sub> and H<sub>2<\/sub>O<\/button>\n    <\/div>\n  <\/div>\n\n<\/div>\n\n<div class=\"irs-info\">\n  <h3 id=\"irsInfoTitle\"><\/h3>\n  <p id=\"irsInfoText\"><\/p>\n  <div class=\"irs-facts\" id=\"irsFacts\"><\/div>\n  <div class=\"irs-key\">\n    <span><i style=\"background:#484e5c\"><\/i>Carbon<\/span>\n    <span><i style=\"background:#eef0f5\"><\/i>Hydrogen<\/span>\n    <span><i style=\"background:#cd342c\"><\/i>Oxygen<\/span>\n    <span><i style=\"background:#3aa048\"><\/i>Chlorine<\/span>\n    <span><i style=\"background:#8c92a0\"><\/i>Bond<\/span>\n    <span><i style=\"background:#14a0a0\"><\/i>Selected bond and its absorption<\/span>\n    <span><i style=\"background:#c9961c\"><\/i>Bending angle<\/span>\n    <span><i style=\"background:#d9433a\"><\/i>Infrared from the Earth<\/span>\n  <\/div>\n<\/div>\n<\/section>\n\n<p class=\"ols-cc-irs-001\">&copy; Dr. Mohammed Al-Fatah &#8211; <a href=\"https:\/\/www.onlinelearningsystem.net\" target=\"_blank\" rel=\"noopener\">onlinelearningsystem.net<\/a><\/p>\n<script src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/JS\/infrared-bonds.js?v=20261003a\"><\/script>\n\n<div class=\"ols-key-box\">\n<p><strong>Key idea:<\/strong> A bond absorbs infrared radiation at the frequency of its own vibration. The wavenumber of the trough identifies the bond.<\/p>\n<\/div>\n<\/article>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">2<\/div>\n<h2>Characteristic Absorptions<\/h2>\n<\/div>\n<p>The region above 1500 cm\u207b\u00b9 is used for <strong>functional group identification<\/strong>, because the absorptions there belong to particular bonds and are found in a data booklet. The exam provides the table; the skill is to match each trough to a bond and to give the range in the answer.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Bond<\/th><th>Where it is found<\/th><th>Wavenumber \/ cm\u207b\u00b9<\/th><th>Appearance<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>C\u2013H<\/strong><\/td><td>alkanes, alkenes, aldehydes, almost every organic compound<\/td><td>2850\u20133100<\/td><td>sharp, medium<\/td><\/tr>\n<tr><td><strong>C=C<\/strong><\/td><td>alkenes<\/td><td>1620\u20131680<\/td><td>medium<\/td><\/tr>\n<tr><td><strong>C=O<\/strong><\/td><td>aldehydes, ketones, carboxylic acids, esters<\/td><td>1680\u20131750<\/td><td>strong, sharp<\/td><\/tr>\n<tr><td><strong>O\u2013H<\/strong><\/td><td>alcohols<\/td><td>3200\u20133600<\/td><td>broad<\/td><\/tr>\n<tr><td><strong>O\u2013H<\/strong><\/td><td>carboxylic acids<\/td><td>2500\u20133300<\/td><td>very broad, overlaps C\u2013H<\/td><\/tr>\n<tr><td><strong>N\u2013H<\/strong><\/td><td>amines<\/td><td>3300\u20133500<\/td><td>medium, often two peaks<\/td><\/tr>\n<tr><td><strong>C\u2013O<\/strong><\/td><td>alcohols, acids, esters<\/td><td>1000\u20131300<\/td><td>strong<\/td><\/tr>\n<tr><td><strong>C\u2013X<\/strong><\/td><td>halogenoalkanes: C\u2013Cl, C\u2013Br<\/td><td>600\u2013800 (C\u2013Cl), 500\u2013600 (C\u2013Br)<\/td><td>in the fingerprint region<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>The O\u2013H absorptions are <strong>broad<\/strong> because hydrogen bonding between molecules spreads the vibration over a range of frequencies; a carboxylic acid O\u2013H is the broadest of all and runs into the C\u2013H region.<\/p><p>An alcohol shows a broad O\u2013H near 3350 and no C=O; a carboxylic acid shows both a very broad O\u2013H and a strong C=O near 1715; an aldehyde or ketone shows the C=O but no O\u2013H.<\/p><p>An alkene&#8217;s C=C is weaker than a C=O and is easy to miss.<\/p>\n<div class=\"ols-figure-card ols-zoom-pop\">\n<div class=\"ols-figure-image\">\n<a class=\"ols-image-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/alcohols-halogenoalkanes-spectra-irspectra-v2.jpg\" target=\"_blank\" rel=\"noopener\" aria-label=\"Open image fullscreen\">\n<img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/alcohols-halogenoalkanes-spectra-irspectra-v2.jpg\" alt=\"Infrared spectra of ethanol and ethanoic acid with the key absorptions labelled, and a table of characteristic absorptions\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/alcohols-halogenoalkanes-spectra-irspectra-v2.jpg\">\n<\/a>\n<\/div>\n<div class=\"ols-figure-caption\"><p>The infrared spectra of ethanol and ethanoic acid with the O\u2013H, C=O, C\u2013H and C\u2013O absorptions labelled and the fingerprint region shaded, beside the wavenumber table.<\/p><\/div>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Exam focus:<\/strong> Write &#8220;absorption at 1680\u20131750 cm\u207b\u00b9 due to C=O&#8221;. The bond, the range from the data sheet and the word absorption (or trough) are the three parts of the mark.<\/p>\n<\/div>\n<\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Check: Which Bond, Which Trough<\/h2>\n<p>Assign absorptions in spectra of compounds not discussed on this page.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-971\" class=\"h5p-iframe\" data-content-id=\"971\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Alcohols, Halogenoalkanes and Spectra Drag: Which Bond, Which Trough\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">3<\/div>\n<h2>The Fingerprint Region<\/h2>\n<\/div>\n<p>Below about 1500 cm\u207b\u00b9 the spectrum contains many overlapping absorptions from bending vibrations and from C\u2013C and C\u2013O stretches.<\/p><p>This <strong>fingerprint region<\/strong> is too complicated to assign bond by bond, but its exact pattern is unique to each compound.<\/p><p>A computer compares the fingerprint region of an unknown with a database of spectra of pure compounds; an exact match identifies the compound and confirms its purity.<\/p>\n\n<div class=\"ols-key-box\">\n<p><strong>Key idea:<\/strong> Above 1500 cm\u207b\u00b9: identify the functional groups. Below 1500 cm\u207b\u00b9: match the fingerprint to a database.<\/p>\n<\/div>\n<div class=\"ols-figure-card ols-zoom-pop\">\n<div class=\"ols-figure-image\">\n<a class=\"ols-image-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/alcohols-halogenoalkanes-spectra-irdecision.jpg\" target=\"_blank\" rel=\"noopener\" aria-label=\"Open image fullscreen\">\n<img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/alcohols-halogenoalkanes-spectra-irdecision.jpg\" alt=\"Infrared spectrum split at 1500 wavenumbers, with a decision tree for functional groups and a fingerprint matching panel.\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/alcohols-halogenoalkanes-spectra-irdecision.jpg\">\n<\/a>\n<\/div>\n<div class=\"ols-figure-caption\"><p>Use the absorptions above 1500 cm\u207b\u00b9 to decide the functional group, then match the fingerprint region below 1500 cm\u207b\u00b9 against a database to identify the compound.<\/p><\/div>\n<\/div>\n<\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Check: Telling Compounds Apart<\/h2>\n<p>Use spectra to distinguish between compounds that are not the examples above.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"972\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">4<\/div>\n<h2>Common Exam Points<\/h2>\n<\/div>\n<h3>Say<\/h3><p>&#8220;A broad absorption at 3200\u20133600 cm\u207b\u00b9 shows an O\u2013H group in an alcohol.&#8221; &#8220;No absorption at 1680\u20131750 cm\u207b\u00b9, so no C=O bond.&#8221; &#8220;The fingerprint region matches the database spectrum of the pure compound.&#8221;<\/p>\n<h3>Do not say<\/h3><p>&#8220;A peak at 1700&#8221; (say absorption or trough, and quote the range). &#8220;The O\u2013H peak&#8221; without saying alcohol or acid.<\/p>\n<h3>Watch for<\/h3><p>Distinguishing questions: name the absorption that one compound has and the other lacks, with the wavenumber range.<\/p>\n<\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Check: Predicting a Spectrum<\/h2>\n<p>Predict the absorptions of compounds not shown on this page.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-973\" class=\"h5p-iframe\" data-content-id=\"973\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Alcohols, Halogenoalkanes and Spectra Quick Choice: Predicting a Spectrum\"><\/iframe><\/div><\/div>\n<\/section>\n<section class=\"ols-faq-card\">\n<h2>FAQs<\/h2>\n<p>Use these quick answers to check infrared spectroscopy.<\/p>\n\n<div class=\"ols-faq-list\">\n<div class=\"ols-faq-item\">\n<h3>Why does the spectrum have troughs rather than peaks?<\/h3>\n<p>The y-axis is transmittance, the fraction of radiation that gets through. Where a bond absorbs, less radiation is transmitted, so the line dips.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Why is the O\u2013H absorption broad?<\/h3>\n<p>Hydrogen bonding between molecules varies the strength of each O\u2013H bond slightly, so the vibrations are spread over a range of wavenumbers. Carboxylic acids hydrogen bond most strongly and give the broadest band.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Can I tell an aldehyde from a ketone by infrared?<\/h3>\n<p>Not reliably. Both show the C=O absorption near 1700 cm\u207b\u00b9. Use the mass spectrum or a chemical test such as Tollens&#8217; reagent or Fehling&#8217;s solution.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>What is the fingerprint region for?<\/h3>\n<p>Matching. Below 1500 cm\u207b\u00b9 the pattern is unique to each compound, so comparing it with a database spectrum identifies the compound and shows whether it is pure.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Do I have to remember the wavenumbers?<\/h3>\n<p>No. The exam gives a data sheet; the skill is to look up the right bond and quote the range in your answer.<\/p>\n<\/div>\n<\/div>\n<\/section>\n<section class=\"ols-related-card\">\n<h2>Related Topic 10C Spectra Pages<\/h2>\n<p>Use these pages to connect the ideas across spectra and the rest of Topic 10.<\/p>\n<div class=\"ols-related-grid\">\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/mass-spectra-of-organic-compounds\/\">Mass Spectra of Organic Compounds<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/identifying-unknown-compounds\/\">Identifying Unknown Compounds<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/\">Topic 10C Spectra Overview<\/a>\n<\/div>\n<\/section>\n<section class=\"ols-attribution-card\">\n        <p><strong>Copyright notice:<\/strong> This OLS revision content, including the explanations, layout, diagrams, tables and embedded learning structure, is authored for Online Learning System by Dr. Mohammed Al-Fatah. It may not be copied, reproduced, redistributed or adapted without written permission.<\/p>\n      <\/section>\n    <\/main>\n  \n\n<script type=\"application\/ld+json\">\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@graph\": [\n    {\n      \"@type\": \"WebPage\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/infrared-spectroscopy\/#webpage\",\n      \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/infrared-spectroscopy\/\",\n      \"name\": \"Infrared Spectroscopy | Topic 10C Spectra | Online Learning System\",\n      \"description\": \"Edexcel International A Level Chemistry revision notes on infrared spectroscopy: bond vibrations, wavenumbers, characteristic absorptions of functional groups, broad O\u2013H bands, the fingerprint region and identifying compounds.\",\n      \"isPartOf\": {\n        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/#website\"\n      },\n      \"breadcrumb\": {\n        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/infrared-spectroscopy\/#breadcrumb\"\n      }\n    },\n    {\n      \"@type\": \"WebSite\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/#website\",\n      \"url\": \"https:\/\/www.onlinelearningsystem.net\/\",\n      \"name\": \"Online Learning System\"\n    },\n    {\n      \"@type\": \"BreadcrumbList\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/infrared-spectroscopy\/#breadcrumb\",\n      \"itemListElement\": [\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 1,\n          \"item\": {\n            \"@type\": \"WebPage\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\",\n            \"name\": \"Revision Notes\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 2,\n          \"item\": {\n            \"@type\": \"WebPage\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\",\n            \"name\": \"A Level Chemistry\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 3,\n          \"item\": {\n            \"@type\": \"WebPage\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\",\n            \"name\": \"Edexcel International\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 4,\n          \"item\": {\n            \"@type\": \"WebPage\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/\",\n            \"name\": \"Topic 10 Alcohols, Halogenoalkanes and Spectra\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 5,\n          \"item\": {\n            \"@type\": \"WebPage\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/\",\n            \"name\": \"Topic 10C Spectra\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 6,\n          \"item\": {\n            \"@type\": \"WebPage\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/infrared-spectroscopy\/\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/infrared-spectroscopy\/\",\n            \"name\": \"Infrared Spectroscopy\"\n          }\n        }\n      ]\n    },\n    {\n      \"@type\": \"Course\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/infrared-spectroscopy\/#course\",\n      \"name\": \"Infrared Spectroscopy\",\n      \"description\": \"Edexcel International A Level Chemistry revision notes on infrared spectroscopy: bond vibrations, wavenumbers, characteristic absorptions of functional groups, broad O\u2013H bands, the fingerprint region and identifying compounds.\",\n      \"provider\": {\n        \"@type\": \"Organization\",\n        \"name\": \"Online Learning System\",\n        \"url\": \"https:\/\/www.onlinelearningsystem.net\/\"\n      },\n      \"educationalLevel\": \"A Level\",\n      \"about\": [\n        \"Alcohols\",\n        \"Halogenoalkanes\",\n        \"Nucleophilic substitution\",\n        \"Elimination\",\n        \"Oxidation of alcohols\",\n        \"Mass spectrometry\",\n        \"Infrared spectroscopy\",\n        \"Organic chemistry\"\n      ],\n      \"hasCourseInstance\": {\n        \"@type\": \"CourseInstance\",\n        \"courseMode\": \"Online\"\n      }\n    },\n    {\n      \"@type\": \"ItemList\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/infrared-spectroscopy\/#relatedtopics\",\n      \"name\": \"Related Topic 10C Spectra Pages\",\n      \"itemListElement\": [\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 1,\n          \"item\": {\n            \"@type\": \"Course\",\n            \"name\": \"Mass Spectra of Organic Compounds\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/mass-spectra-of-organic-compounds\/\",\n            \"description\": \"Edexcel International A Level Chemistry revision notes on mass spectra of organic compounds: molecular ion, m\/z, fragmentation patterns, common fragments, M+2 peaks for chlorine and bromine.\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 2,\n          \"item\": {\n            \"@type\": \"Course\",\n            \"name\": \"Identifying Unknown Compounds\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-10-alcohols-halogenoalkanes-and-spectra\/10c-spectra\/identifying-unknown-compounds\/\",\n            \"description\": \"Edexcel International A Level Chemistry revision notes on identifying unknown organic compounds: combining the molecular ion, fragmentation, infrared absorptions and chemical tests, with a worked example.\"\n          }\n        }\n      ]\n    }\n  ]\n}\n<\/script>\n\n<\/section>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Revision Notes \/ A Level Chemistry \/ Edexcel International \/ Topic 10 Alcohols, Halogenoalkanes and Spectra \/ Topic 10C Spectra \/ Infrared Spectroscopy Infrared Spectroscopy A concise revision guide to infrared spectroscopy: why bonds absorb infrared radiation, wavenumbers and transmittance, the characteristic absorptions of C\u2013H, C=C, C=O, O\u2013H, N\u2013H and C\u2013X bonds, the fingerprint region. [&hellip;]<\/p>\n","protected":false},"author":12,"featured_media":0,"parent":10902,"menu_order":1,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-10913","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/10913","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/comments?post=10913"}],"version-history":[{"count":2,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/10913\/revisions"}],"predecessor-version":[{"id":14195,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/10913\/revisions\/14195"}],"up":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/10902"}],"wp:attachment":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/media?parent=10913"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}