{"id":4813,"date":"2026-06-03T06:24:22","date_gmt":"2026-06-03T05:24:22","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/iupac-rules\/"},"modified":"2026-10-14T09:06:39","modified_gmt":"2026-10-14T08:06:39","slug":"iupac-rules","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/iupac-rules\/","title":{"rendered":"IUPAC Rules"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-iupac-rules-page\">\n  <style>.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      --soft-orange: #fff7ed;\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    }.ols-revision-page * {\n      box-sizing: border-box;\n    }.ols-main {\n      min-width: 0;\n      max-width: 970px;\n    }.ols-breadcrumbs {\n      display: flex;\n      flex-wrap: wrap;\n      gap: 8px;\n      margin: 10px 0 22px;\n      font-size: 15px;\n      color: var(--grey-text);\n    }.ols-breadcrumbs a, .ols-breadcrumbs span {\n      color: var(--grey-text);\n      text-decoration: none;\n      font-weight: 600;\n    }.ols-breadcrumbs a:hover {\n      color: var(--blue);\n      text-decoration: underline;\n      text-underline-offset: 3px;\n    }.ols-title-card, .ols-note-card, .ols-h5p-card, .ols-related-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    }.ols-title-card {\n      background: linear-gradient(135deg, #ffffff 0%, #f8fbff 100%);\n    }.ols-title-card h1 {\n      margin: 0 0 18px;\n      font-size: clamp(36px, 5vw, 58px);\n      line-height: 1.08;\n      font-weight: 800;\n      letter-spacing: -0.04em;\n      color: #111827;\n    }.ols-page-intro {\n      font-size: 19px;\n      line-height: 1.7;\n      font-weight: 300;\n      color: var(--body-text);\n      margin: 0 0 22px;\n    }.ols-badges {\n      display: flex;\n      flex-wrap: wrap;\n      gap: 12px;\n      margin-bottom: 22px;\n    }.ols-badge {\n      display: inline-flex;\n      align-items: center;\n      padding: 9px 14px;\n      border-radius: 999px;\n      background: #ffffff;\n      border: 1px solid var(--border);\n      font-size: 15px;\n      font-weight: 600;\n      color: var(--navy);\n    }.ols-note-card.soft {\n      background: linear-gradient(135deg, #ffffff 0%, 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#ffffff;\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 18px;\n      box-shadow: var(--inner-shadow);\n    }.ols-definition-tile h3 {\n      margin: 0 0 8px;\n      font-size: 20px;\n      line-height: 1.25;\n      color: var(--navy);\n    }.ols-definition-tile p {\n      margin: 0;\n      font-size: 15px;\n      line-height: 1.55;\n    }.ols-figure-card {\n      margin: 26px 0 4px;\n      border: 1px solid var(--border);\n      border-radius: 26px;\n      overflow: hidden;\n      background: #ffffff;\n      box-shadow: var(--inner-shadow);\n    }.ols-figure-image {\n      width: 100%;\n      min-height: 300px;\n      display: flex;\n      align-items: center;\n      justify-content: center;\n      background: #ffffff;\n      padding: 24px;\n    }.ols-figure-image img {\n      max-width: 100%;\n      height: auto;\n      display: block;\n    }.ols-figure-caption {\n      padding: 18px 24px 22px;\n      background: linear-gradient(135deg, #ffffff, 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linear-gradient(135deg, #ffffff, #f8fbff);\n    }.ols-mini-figure-caption p {\n      margin: 0;\n      font-size: 15px;\n      line-height: 1.55;\n      font-style: italic;\n      color: #5f6b85;\n    }.ols-table-wrap {\n      overflow: hidden;\n      border-radius: 22px;\n      border: 1px solid var(--border);\n      background: #ffffff;\n      margin-top: 18px;\n    }.ols-table {\n      width: 100%;\n      border-collapse: collapse;\n      table-layout: fixed;\n    }.ols-table th {\n      background: var(--navy);\n      color: #ffffff;\n      padding: 16px;\n      text-align: left;\n      font-size: clamp(14px, 1.2vw, 17px);\n      font-weight: 600;\n      overflow-wrap: anywhere;\n    }.ols-table td {\n      padding: 16px;\n      border-bottom: 1px solid var(--border);\n      font-size: clamp(14px, 1.15vw, 16px);\n      line-height: 1.45;\n      color: var(--body-text);\n      vertical-align: top;\n      overflow-wrap: anywhere;\n    }.ols-table tr:last-child td {\n      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36px;\n      color: #ffffff;\n      box-shadow: var(--shadow);\n      text-align: center;\n      margin: 30px 0 24px;\n    }.ols-unlock h2 {\n      margin: 0 0 12px;\n      font-size: clamp(30px, 4vw, 46px);\n      line-height: 1.15;\n      font-weight: 800;\n      color: #ffffff;\n      text-align: center;\n    }.ols-unlock p {\n      margin: 0 auto 24px;\n      max-width: 700px;\n      font-size: 20px;\n      line-height: 1.6;\n      font-weight: 300;\n      text-align: center;\n      color: #ffffff;\n    }.ols-cta-button {\n      display: inline-flex;\n      align-items: center;\n      justify-content: center;\n      padding: 14px 26px;\n      border-radius: 999px;\n      background: #ffffff;\n      color: var(--navy);\n      text-decoration: none;\n      font-weight: 700;\n      transition: background 0.2s ease, color 0.2s ease, transform 0.2s ease;\n    }.ols-cta-button:hover {\n      background: #f8fbff;\n      color: var(--blue);\n      transform: translateY(-1px);\n    }.ols-related-grid {\n      display: grid;\n      grid-template-columns: repeat(3, minmax(0, 1fr));\n      gap: 16px;\n      margin-top: 18px;\n    }.ols-related-item {\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 18px;\n      background: #ffffff;\n      color: var(--navy);\n      text-decoration: none;\n      font-weight: 600;\n      line-height: 1.5;\n      transition: transform 0.2s ease, box-shadow 0.2s ease;\n    }.ols-related-item:hover {\n      transform: translateY(-2px);\n      box-shadow: 0 10px 22px rgba(28, 36, 75, 0.08);\n    }@media (max-width: 1050px) {.ols-main {\n        max-width: none;\n      }.ols-related-grid, .ols-definition-grid, .ols-image-grid {\n        grid-template-columns: repeat(2, minmax(0, 1fr));\n      }\n    }@media (max-width: 760px) {.ols-title-card, .ols-note-card, .ols-h5p-card, .ols-related-card, .ols-unlock {\n        padding: 24px 18px;\n        border-radius: 22px;\n      }.ols-note-title {\n        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#ffffff;\n        box-shadow: var(--inner-shadow);\n      }.ols-table td {\n        border-bottom: 1px solid var(--border);\n        padding: 14px 16px;\n        overflow-wrap: anywhere;\n      }.ols-table td:last-child {\n        border-bottom: none;\n      }.ols-table td::before {\n        content: attr(data-label);\n        display: block;\n        margin-bottom: 6px;\n        font-size: 13px;\n        font-weight: 700;\n        color: var(--blue);\n      }\n    }\n\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\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\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\n    .ols-author-content {\n      min-width: 0;\n    }\n\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\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\n    .ols-linkedin-pill,\n    .ols-linkedin-pill:visited,\n    .ols-linkedin-pill:hover,\n    .ols-linkedin-pill:focus,\n    .ols-linkedin-pill:active {\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 !important;\n      text-decoration: none !important;\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\n    .ols-linkedin-pill::before {\n      content: \"\";\n      position: absolute;\n      top: 0;\n      left: -120%;\n      width: 100%;\n      height: 100%;\n      background: linear-gradient(120deg, rgba(255,255,255,0) 0%, rgba(255,255,255,0.28) 50%, rgba(255,255,255,0) 100%);\n      transition: left 0.7s ease;\n    }\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\n    .ols-linkedin-pill:hover::before {\n      left: 120%;\n    }\n\n    .ols-linkedin-icon {\n      width: 18px;\n      height: 18px;\n      display: block;\n      flex-shrink: 0;\n      position: relative;\n      z-index: 1;\n    }\n\n    .ols-linkedin-pill span {\n      position: relative;\n      z-index: 1;\n      color: #ffffff !important;\n    }\n\n    @media (max-width: 640px) {\n      .ols-author {\n        align-items: flex-start;\n        padding: 22px 18px;\n        border-radius: 22px;\n      }\n\n      .ols-author-avatar-img {\n        width: 72px;\n        height: 72px;\n      }\n\n      .ols-author-title {\n        font-size: 24px;\n      }\n\n      .ols-author-description {\n        font-size: 15px;\n      }\n    }\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\">\r\n  <div class=\"ols-sidebar-header\">\r\n    <h3>Revision Notes<\/h3>\r\n    <p>A Level Chemistry<\/p>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Topic 6 Organic Chemistry I<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/\">Introduction to Organic Chemistry<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/iupac-rules\/\">IUPAC Rules<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/alkene\/\">Alkene<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/alcohol\/\">Alcohol<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/halogenoalkanes\/\">Halogenoalkanes<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/aldehyde\/\">Aldehyde<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/ketone\/\">Ketone<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/carboxylic-acid\/\">Carboxylic Acid<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/ester\/\">Ester<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/isomerism\/\">Isomerism<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/\">Alkanes<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/\">Alkanes from Crude Oil<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/fractional-distillation\/\">Fractional Distillation<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/cracking\/\">Cracking<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/reforming\/\">Reforming<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/\">Alkanes as Fuel<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/combustion\/\">Combustion<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/oxides-of-sulfur\/\">Oxides of Sulfur<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/oxides-of-nitrogen\/\">Oxides of Nitrogen<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/catalytic-converter\/\">Catalytic Converter<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/alternative-fuel\/\">Alternative Fuel<\/a>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/\">Reactions of Alkanes<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/free-radical-substitution\/\">Free Radical Substitution<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/initiation\/\">Initiation<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/propagation\/\">Propagation<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/termination\/\">Termination<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/further-substitution\/\">Further Substitution<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/\">Alkenes<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/alkene-bonding\/\">Alkene Bonding<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/geometric-isomerism\/\">Geometric Isomerism<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/electrophilic-addition-mechanism\/\">Electrophilic Addition Mechanism<\/a>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/\">Reactions of Alkenes<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/halogens\/\">Halogens<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/hydrogen-halide\/\">Hydrogen Halide<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/bromine-water\/\">Bromine Water<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/hydrogen\/\">Hydrogen<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/steam\/\">Steam<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/kmno4\/\">KMnO4<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/polymerisation-reactions\/\">Polymerisation Reactions<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/polymer-waste\/\">Polymer Waste<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/halogenoalkanes\/\">Halogenoalkanes<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alcohols\/\">Alcohols<\/a>\r\n      <\/li>\r\n\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Next Topics<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-7-modern-analytical-techniques-i\/\">Topic 7 Modern Analytical Techniques I<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-5-formulae-equations-and-amounts-of-substance\/\">Topic 5 Formulae, Equations &amp; Amounts<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/\">Topic 4 Inorganic Chemistry &amp; The Periodic Table<\/a>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n<\/aside>\r\n\r\n<script>\r\n(function() {\r\n  function normalisePath(path) {\r\n    return String(path || '')\r\n      .split('?')[0]\r\n      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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\/\">Edexcel<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/\">Topic 6 Organic Chemistry I<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/\">Introduction to Organic Chemistry<\/a> \/\n        <span>IUPAC Rules<\/span>\n      <\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>IUPAC Rules<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to the key IUPAC naming rules used in A Level organic chemistry, including formula types, displayed formulae, skeletal formulae, carbon chain prefixes, functional group naming and numbering rules.<\/p>\n\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">Paper 2<\/div>\n          <div class=\"ols-badge\">Topic 6: Organic Chemistry I<\/div>\n          <div class=\"ols-badge\">9CH0\/02<\/div>\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 in a Displayed Formula<\/h2>\n<p>Before you start, check that you remember how many bonds each kind of atom forms and what makes a compound a hydrocarbon.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"712\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">1<\/div>\n          <h2>Key Organic Chemistry Definitions<\/h2>\n        <\/div>\n\n        <p>Before naming organic compounds, you need to recognise the basic language used to describe formulae, bonding and families of compounds.<\/p>\n\n        <div class=\"ols-definition-grid\">\n          <div class=\"ols-definition-tile\">\n            <h3>Hydrocarbon<\/h3>\n            <p>A compound consisting of hydrogen and carbon only.<\/p>\n          <\/div>\n\n          <div class=\"ols-definition-tile\">\n            <h3>Saturated<\/h3>\n            <p>A compound containing single carbon-carbon bonds only.<\/p>\n          <\/div>\n\n          <div class=\"ols-definition-tile\">\n            <h3>Unsaturated<\/h3>\n            <p>A compound containing at least one C=C double bond.<\/p>\n          <\/div>\n\n          <div class=\"ols-definition-tile\">\n            <h3>Molecular formula<\/h3>\n            <p>The formula showing the actual number of each type of atom in a molecule.<\/p>\n          <\/div>\n\n          <div class=\"ols-definition-tile\">\n            <h3>Empirical formula<\/h3>\n            <p>The simplest whole number ratio of atoms of each element in a compound.<\/p>\n          <\/div>\n\n          <div class=\"ols-definition-tile\">\n            <h3>General formula<\/h3>\n            <p>An algebraic formula for a homologous series, such as C<sub>n<\/sub>H<sub>2n<\/sub> for alkenes.<\/p>\n          <\/div>\n\n          <div class=\"ols-definition-tile\">\n            <h3>Structural formula<\/h3>\n            <p>The minimal detail needed to show the arrangement of atoms in a molecule, such as CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>2<\/sub>CH<sub>3<\/sub>.<\/p>\n          <\/div>\n\n          <div class=\"ols-definition-tile\">\n            <h3>Displayed formula<\/h3>\n            <p>A formula showing all covalent bonds present in a molecule.<\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Key idea:<\/strong> IUPAC naming depends on identifying the carbon skeleton, the functional group and the correct numbering system.<\/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>Quick Check: Which Kind of Formula?<\/h2>\n<p>Decide quickly which term describes each formula or compound.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-64\" class=\"h5p-iframe\" data-content-id=\"64\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"IUPAC Rules Quick Sort: Types of Formula and Hydrocarbon\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">2<\/div>\n          <h2>Displayed and Skeletal Formulae<\/h2>\n        <\/div>\n\n        <p>When drawing organic compounds, add hydrogen atoms so that each carbon forms <strong>four bonds<\/strong>. In saturated hydrocarbons, the arrangement of bonds around each carbon atom is <strong>tetrahedral<\/strong>, with a bond angle of approximately <strong>109.5\u00b0<\/strong>.<\/p>\n\n        <p>A <strong>skeletal formula<\/strong> is a simplified way of representing an organic molecule. Hydrogen atoms bonded to carbon are omitted, showing only the carbon skeleton and any functional groups attached.<\/p>\n\n        <div class=\"ols-image-grid\">\n          <div class=\"ols-mini-figure\">\n            <div class=\"ols-mini-figure-image\">\n              <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-mv-01-2-methylbutane.svg\" alt=\"Skeletal formulae of 2-methylbutane\" width=\"485\" height=\"354\">\n            <\/div>\n            <div class=\"ols-mini-figure-caption\">\n              <p>2-methylbutane shows a branched carbon skeleton with four bonds around each carbon.<\/p>\n            <\/div>\n          <\/div>\n\n          <div class=\"ols-mini-figure\">\n            <div class=\"ols-mini-figure-image\">\n              <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-mv-02-displayed.svg\" alt=\"Displayed formulae of ethane\" width=\"410\" height=\"363\">\n            <\/div>\n            <div class=\"ols-mini-figure-caption\">\n              <p>Ethane can be represented with all C-H and C-C covalent bonds shown.<\/p>\n            <\/div>\n          <\/div>\n\n          <div class=\"ols-mini-figure\">\n            <div class=\"ols-mini-figure-image\">\n              <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/mol-but-2-ene.svg\" alt=\"Skeletal formula of but-2-ene\" width=\"378\" height=\"200\">\n            <\/div>\n            <div class=\"ols-mini-figure-caption\">\n              <p>But-2-ene uses a skeletal formula, with carbon atoms at line ends and vertices.<\/p>\n            <\/div>\n          <\/div>\n\n          <div class=\"ols-mini-figure\">\n            <div class=\"ols-mini-figure-image\">\n              <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/mol-butan-1-ol.svg\" alt=\"Skeletal formula of butan-1-ol\" width=\"492\" height=\"200\">\n            <\/div>\n            <div class=\"ols-mini-figure-caption\">\n              <p>Functional groups, such as OH in alcohols, are shown explicitly in skeletal formulae.<\/p>\n            <\/div>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Exam focus:<\/strong> In skeletal formulae, carbon atoms and carbon-bonded hydrogen atoms are usually not written, but heteroatoms and functional groups must still be shown.<\/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>Quick Check: Read a Skeletal Formula<\/h2>\n<p>Picture the skeletal formula described and work out its molecular formula.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-67\" class=\"h5p-iframe\" data-content-id=\"67\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"IUPAC Rules MCQ: Molecular Formula from a Skeletal Formula\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">3<\/div>\n          <h2>Naming Carbon Chains<\/h2>\n        <\/div>\n\n        <p>The first step in IUPAC naming is to identify and count the <strong>longest continuous carbon chain<\/strong>. This gives the parent name of the compound.<\/p>\n        <p>Next, identify any <strong>branched side chains<\/strong> and count the number of carbon atoms in each branch. The correct prefix is then added to the parent name.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Code<\/th>\n                <th>Number of carbons<\/th>\n                <th>Used in parent names such as<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Code\">meth<\/td>\n                <td data-label=\"Number of carbons\">1<\/td>\n                <td data-label=\"Used in parent names such as\">methane<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Code\">eth<\/td>\n                <td data-label=\"Number of carbons\">2<\/td>\n                <td data-label=\"Used in parent names such as\">ethane, ethene<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Code\">prop<\/td>\n                <td data-label=\"Number of carbons\">3<\/td>\n                <td data-label=\"Used in parent names such as\">propane, propene<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Code\">but<\/td>\n                <td data-label=\"Number of carbons\">4<\/td>\n                <td data-label=\"Used in parent names such as\">butane, but-2-ene<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Code\">pent<\/td>\n                <td data-label=\"Number of carbons\">5<\/td>\n                <td data-label=\"Used in parent names such as\">pentane<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Code\">hex<\/td>\n                <td data-label=\"Number of carbons\">6<\/td>\n                <td data-label=\"Used in parent names such as\">hexane<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Code\">hept<\/td>\n                <td data-label=\"Number of carbons\">7<\/td>\n                <td data-label=\"Used in parent names such as\">heptane<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Code\">oct<\/td>\n                <td data-label=\"Number of carbons\">8<\/td>\n                <td data-label=\"Used in parent names such as\">octane<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Code\">non<\/td>\n                <td data-label=\"Number of carbons\">9<\/td>\n                <td data-label=\"Used in parent names such as\">nonane<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Code\">dec<\/td>\n                <td data-label=\"Number of carbons\">10<\/td>\n                <td data-label=\"Used in parent names such as\">decane<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-cd-02-dimethylheptane.svg\" alt=\"Skeletal formula of 3,5-dimethylheptane with the seven-carbon chain highlighted and numbered, methyl branches on carbons 3 and 5\" width=\"747\" height=\"391\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <p>The longest continuous chain is counted first, then methyl branches are located using numbers.<\/p>\n          <\/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>Quick Check: Find the Longest Chain<\/h2>\n<p>Name a branched alkane whose longest chain is not the one written in a straight line.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-66\" class=\"h5p-iframe\" data-content-id=\"66\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"IUPAC Rules MCQ: Finding the Longest Chain in a Branched Alkane\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">4<\/div>\n          <h2>Functional Groups and Suffix Rules<\/h2>\n        <\/div>\n\n        <p>A <strong>functional group<\/strong> is an atom or group of atoms responsible for giving a homologous series its characteristic chemical reactions. In names, a functional group may be shown using either a <strong>prefix<\/strong> or a <strong>suffix<\/strong>.<\/p>\n\n        <div class=\"ols-rule-list\">\n          <div class=\"ols-rule-item\">\n            <h3>Suffix starts with a vowel<\/h3>\n            <p>If the suffix starts with a vowel, the final <strong>-e<\/strong> is removed from the parent alkane name. Examples include propan-1-ol, butan-1-amine, ethanoic acid, ethanoyl chloride and butanamide.<\/p>\n          <\/div>\n\n          <div class=\"ols-rule-item\">\n            <h3>Suffix starts with a consonant<\/h3>\n            <p>If the suffix starts with a consonant, the final <strong>-e<\/strong> is not removed from the parent alkane name. Examples include propanenitrile and pentane-2,4-dione.<\/p>\n          <\/div>\n\n          <div class=\"ols-rule-item\">\n            <h3>Two or more of the same functional group<\/h3>\n            <p>If there are two or more of the same functional group and di- or tri- is used, the final <strong>-e<\/strong> is not removed. Examples include ethane-1,2-diol and propane-1,2,3-triol.<\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/mol-butan-1-ol.svg\" alt=\"Skeletal formula of butan-1-ol\" width=\"492\" height=\"200\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <p>The number 1 shows that the OH group is attached to the first carbon in the chain.<\/p>\n          <\/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>Quick Check: Keep the e or Drop It?<\/h2>\n<p>Drag the correctly written name to each of five compounds that are not on this page.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-1069\" class=\"h5p-iframe\" data-content-id=\"1069\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"IUPAC Rules Drag: Naming Five New Compounds\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card orange\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">5<\/div>\n          <h2>Numbering Rules and Alphabetical Order<\/h2>\n        <\/div>\n\n        <p>Numbers are only included in names when they are needed to avoid ambiguity. When numbering a carbon chain, functional groups take priority over branched side chains when assigning the <strong>lowest possible number<\/strong>.<\/p>\n\n        <p>Words and numbers in organic names are separated using <strong>dashes<\/strong>. When more than one number is used, numbers are separated by <strong>commas<\/strong>.<\/p>\n\n        <p>If a molecule contains more than one functional group or side chain, the groups are listed in <strong>alphabetical order<\/strong>, ignoring multiplicative prefixes such as di- or tri-.<\/p>\n\n        <div class=\"ols-image-grid\">\n          <div class=\"ols-mini-figure\">\n            <div class=\"ols-mini-figure-image\">\n              <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/mol-2-2-dichloro-1-fluorobutane.svg\" alt=\"Skeletal formula of 2,2-dichloro-1-fluorobutane\" width=\"464\" height=\"279\">\n            <\/div>\n            <div class=\"ols-mini-figure-caption\">\n              <p>2,2-dichloro-1-fluorobutane shows comma-separated numbers and alphabetical ordering by functional group prefix.<\/p>\n            <\/div>\n          <\/div>\n\n          <div class=\"ols-mini-figure\">\n            <div class=\"ols-mini-figure-image\">\n              <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/mol-3-bromo-1-fluoropentane.svg\" alt=\"Skeletal formula of 3-bromo-1-fluoropentane\" width=\"542\" height=\"301\">\n            <\/div>\n            <div class=\"ols-mini-figure-caption\">\n              <p>Bromo is written before fluoro because prefixes are listed alphabetically.<\/p>\n            <\/div>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Remember:<\/strong> The correct name depends on choosing the longest chain, assigning the lowest possible numbers and writing substituents in alphabetical order.<\/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\/10\/t4-img-01-nameanatomy.jpg\" target=\"_blank\" rel=\"noopener\" aria-label=\"Open image fullscreen\">\n<img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-img-01-nameanatomy.jpg\" alt=\"The name 4-chloro-3-methylpentan-2-ol split into colour-coded locants, prefixes, stem and suffix, with four naming rules\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-img-01-nameanatomy.jpg\">\n<\/a>\n<\/div>\n<div class=\"ols-figure-caption\"><p>Longest chain, main group, lowest locants, alphabetical prefixes, then punctuation: the same five steps name every 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>Quick Check: Naming in the Right Order<\/h2>\n<p>Put the steps for naming a branched alcohol into the order in which you would carry them out.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-714\" class=\"h5p-iframe\" data-content-id=\"714\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"IUPAC Rules Sort: Steps to Name a Branched Alcohol\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">6<\/div>\n          <h2>Homologous Series and Functional Group Priority<\/h2>\n        <\/div>\n\n        <p>A <strong>homologous series<\/strong> is a family of organic compounds with the same functional group and the same general formula.<\/p>\n<p>Members of a homologous series show a gradual change in physical properties as chain length increases, but similar chemical properties because they contain the same functional group.<\/p>\n\n        <p>Each successive compound in a homologous series differs from the previous compound by a <strong>CH<sub>2<\/sub><\/strong> unit.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Priority rule<\/th>\n                <th>What it means<\/th>\n                <th>Example exam wording<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Priority rule\">Highest priority group<\/td>\n                <td data-label=\"What it means\">The functional group with the highest priority is given the suffix and the lowest possible number.<\/td>\n                <td data-label=\"Example exam wording\">Identify the principal functional group before numbering the chain.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Priority rule\">Other functional groups<\/td>\n                <td data-label=\"What it means\">Other functional groups are named using prefixes.<\/td>\n                <td data-label=\"Example exam wording\">Halogeno groups such as bromo, chloro and fluoro are written as prefixes.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Priority rule\">Double and triple bonds<\/td>\n                <td data-label=\"What it means\">Alkenes and alkynes use suffixes even when another functional group is present.<\/td>\n                <td data-label=\"Example exam wording\">Name the carbon chain and include the position of the C=C bond if required.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Functional group priority, highest to lowest:<\/strong> carboxylic acids &gt; aldehydes &gt; ketones &gt; alcohols &gt; alkenes &gt; halogenoalkanes.<\/p>\n        <\/div>\n\n        <div class=\"ols-image-grid\">\n          <div class=\"ols-mini-figure\">\n            <div class=\"ols-mini-figure-image\">\n              <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/mol-cyclohexene.svg\" alt=\"Skeletal formula of cyclohexene\" width=\"300\" height=\"324\">\n            <\/div>\n            <div class=\"ols-mini-figure-caption\">\n              <p>Cyclohexene contains a C=C double bond in a cyclic carbon skeleton.<\/p>\n            <\/div>\n          <\/div>\n\n          <div class=\"ols-mini-figure\">\n            <div class=\"ols-mini-figure-image\">\n              <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/mol-cyclohexane.svg\" alt=\"Skeletal formula of cyclohexane\" width=\"300\" height=\"324\">\n            <\/div>\n            <div class=\"ols-mini-figure-caption\">\n              <p>Cyclohexane is saturated because it contains carbon-carbon single bonds only.<\/p>\n            <\/div>\n          <\/div>\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\/10\/t4-img-42-stemsseries.jpg\" target=\"_blank\" rel=\"noopener\" aria-label=\"Open image fullscreen\">\n<img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-img-42-stemsseries.jpg\" alt=\"Table of stems meth- to dec- and eight homologous series with general formulae, name endings and examples\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-img-42-stemsseries.jpg\">\n<\/a>\n<\/div>\n<div class=\"ols-figure-caption\"><p>Each series has its own general formula and name ending; the stem counts the carbons in the main chain.<\/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>Quick Check: Spot the Correct Name<\/h2>\n<p>In each round pick the one accurate statement about a name or a homologous series.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-715\" class=\"h5p-iframe\" data-content-id=\"715\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"IUPAC Rules Summary: Spot the Correct Name\"><\/iframe><\/div><\/div>\n<\/section>\n\n      \n\n      <section class=\"ols-faq-card\">\n        <h2>FAQs<\/h2>\n        <p>These questions cover the naming steps students most often get wrong.<\/p>\n        <div class=\"ols-faq-list\">\n          <div class=\"ols-faq-item\">\n            <h3>Do I count the longest chain or the chain drawn in a straight line?<\/h3>\n            <p>Count the longest continuous chain, even if it bends round a corner in the drawing. A chain drawn straight is often not the longest one.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>When do I drop the final e of the alkane name?<\/h3>\n            <p>Drop it when the suffix starts with a vowel, as in propan-1-ol. Keep it before a consonant or a di- or tri- suffix, as in ethane-1,2-diol.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Does dimethyl go under d or m in alphabetical order?<\/h3>\n            <p>Under m. Multiplying prefixes such as di-, tri- and tetra- are ignored when the substituents are put in alphabetical order, so bromo comes before dimethyl.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Which group gets the lowest number when there are several?<\/h3>\n            <p>The principal functional group, the one that gives the suffix. Only after that are the lowest numbers given to the other substituents.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why do members of a homologous series react in the same way?<\/h3>\n            <p>They share the same functional group, and the functional group decides the reactions. Chain length changes physical properties, not the type of reaction.<\/p>\n          <\/div>\n        <\/div>\n      <\/section>\n\n      <!-- author card (moved to the end, 10 Oct 2026) -->\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\n        class=\"ols-linkedin-pill\"\n        href=\"https:\/\/www.linkedin.com\/in\/doctormohammedfatah\/\"\n        target=\"_blank\"\n        rel=\"noopener noreferrer\"\n      >\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        <span>View LinkedIn Profile<\/span>\n      <\/a>\n\n    <\/div>\n\n  <\/div>\n\n\n<section class=\"ols-related-card\">\n        <h2>Related Organic Chemistry Revision Notes<\/h2>\n        <p>Continue through Topic 6 by linking IUPAC naming to introductory organic chemistry, alkanes and alkenes.<\/p>\n\n        <div class=\"ols-related-grid\">\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/\">Introduction to Organic Chemistry<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/\">Alkanes<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/\">Alkenes<\/a>\n        <\/div>\n      <\/section>\n\n      <!-- OLS Author Copyright Footprint \/ Attribution Card -->\n      <section class=\"ols-attribution-card ols-attr-std\" aria-label=\"Copyright notice\">\n<style id=\"ols-attribution-card-css\">.ols-attribution-card.ols-attr-std{background:linear-gradient(135deg,#ffffff,#f8fbff);border:1px solid rgba(28,36,75,0.14);border-radius:28px;box-shadow:0 18px 45px rgba(28,36,75,0.10);padding:34px;margin:24px 0;overflow:hidden;font-family:Poppins,Arial,sans-serif;box-sizing:border-box}.ols-attribution-card.ols-attr-std *{box-sizing:border-box}.ols-attribution-card.ols-attr-std p{margin:0;font-size:14px;line-height:1.65;font-weight:300;color:#667085}.ols-attribution-card.ols-attr-std strong{font-weight:700;color:#1C244B}@media (max-width:760px){.ols-attribution-card.ols-attr-std{padding:24px 18px;border-radius:22px}}<\/style>\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<\/section>\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\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/iupac-rules\/#webpage\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/iupac-rules\/\",\n            \"name\": \"IUPAC Rules - Edexcel A Level Chemistry\",\n            \"headline\": \"IUPAC Rules\",\n            \"description\": \"A Level Chemistry revision notes covering IUPAC rules, organic formulae, displayed formulae, skeletal formulae, carbon chain naming, functional group suffixes and 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