{"id":3508,"date":"2026-05-14T08:00:14","date_gmt":"2026-05-14T07:00:14","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/?page_id=3508"},"modified":"2026-06-28T05:54:39","modified_gmt":"2026-06-28T04:54:39","slug":"iupac-rules","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/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 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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  <\/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 4 Organic Chemistry &amp; Alkanes<\/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-international\/topic-4-organic-chemistry-and-alkanes\/hazard-and-risk\/\">Hazard &amp; Risk<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/ester\/\">Ester<\/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-international\/topic-4-organic-chemistry-and-alkanes\/isomerism\/\">Isomerism<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-alkanes\/reactions\/further-substitution\/\">Further Substitution<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\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-international\/topic-5-alkenes\/\">Alkenes<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-6-energetics\/\">Energetics<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-7-intermolecular-forces\/\">Intermolecular Forces<\/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      .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, 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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        <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\">Exam board: Edexcel International<\/div>\n          <div class=\"ols-badge\">Topic 4: Organic Chemistry &amp; Alkanes<\/div>\n          <div class=\"ols-badge\">Level: A Level Chemistry<\/div>\n        <\/div>\n\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        <span>View LinkedIn Profile<\/span>\n      <\/a>\n\n    <\/div>\n\n  <\/div>\n      <\/header>\n\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\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\/05\/2-methylbutane.svg\" alt=\"2-methylbutane structure\">\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\/05\/ethane.svg\" alt=\"Ethane displayed formula\">\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\/05\/but-2-ene.svg\" alt=\"But-2-ene skeletal formula\">\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\/05\/butan-1-ol.svg\" alt=\"Butan-1-ol skeletal formula\">\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\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\/05\/34-dimethylheptane.svg\" alt=\"3,4-dimethylheptane skeletal structure\">\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\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\/05\/butan-1-ol.svg\" alt=\"Butan-1-ol structure\">\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\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\/05\/22-dichloro-1-fluorobutane.svg\" alt=\"2,2-dichloro-1-fluorobutane skeletal structure\">\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\/05\/3-bromo-1-fluoropentane.svg\" alt=\"3-bromo-1-fluoropentane skeletal structure\">\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      <\/article>\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. 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\/05\/cyclohexene.svg\" alt=\"Cyclohexene skeletal structure\">\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\/05\/cyclohexane.svg\" alt=\"Cyclohexane skeletal structure\">\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      <\/article>\n\n      <section class=\"ols-h5p-card\">\n        <h2>Check Your Understanding<\/h2>\n        <p>Use these short activities to check the key ideas before moving on to the individual functional group pages.<\/p>\n\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=\"T4.2.1 Drag: IUPAC Rules Key Concepts\"><\/iframe><\/div><\/div>\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=\"T4.2.3 MCQ: Longest Carbon Chain\"><\/iframe><\/div><\/div>\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=\"T4.2.3 MCQ: Longest Carbon Chain\"><\/iframe><\/div><\/div>\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=\"T4.2.4 MCQ: Functional Group Numbering\"><\/iframe><\/div><\/div>\n        <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-301\" class=\"h5p-iframe\" data-content-id=\"301\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"IUPAC name of a branched alkane from skeletal structure\"><\/iframe><\/div><\/div>\n      <\/section>\n\n      <section class=\"ols-course-cta-alkenes\" 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         <\/a>\n\n            <div class=\"ols-course-cta-content\">\n\n              <div class=\"ols-course-cta-header-row\">\n\n                <div class=\"ols-course-cta-kicker\">\n                  Complete Topic 4A\/B Organic Chemistry &amp; Alkanes Course\n                <\/div>\n\n                <a class=\"ols-course-button ols-course-button-top\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/organic-chemistry-alkanes-topic-4ab-edexcel-international\/\">\n                  View Course\n                <\/a>\n\n              <\/div>\n\n              <h2>\n                Master Organic Chemistry and Alkanes for Edexcel International A Level Chemistry\n              <\/h2>\n\n            <\/div>\n\n          <\/div>\n\n          <div class=\"ols-course-cta-intro-stats\">\n\n            <p class=\"ols-course-cta-intro\">\n              Continue from these free revision notes into the full Topic 4A\/B Organic Chemistry and Alkanes course, with guided video teaching, diagnostic MCQ practice, teacher-marked short-answer questions and a specification assignment with a personalised progress report.\n            <\/p>\n\n            <div class=\"ols-course-cta-stats\">\n\n              <div class=\"ols-course-stat\">\n                <span>Guided learning<\/span>\n                <strong>16 hours<\/strong>\n              <\/div>\n\n              <div class=\"ols-course-stat\">\n                <span>Video lessons<\/span>\n                <strong>430 mins<\/strong>\n              <\/div>\n\n              <div class=\"ols-course-stat\">\n                <span>MCQ practice<\/span>\n                <strong>73 marks<\/strong>\n              <\/div>\n\n              <div class=\"ols-course-stat\">\n                <span>SAQ practice<\/span>\n                <strong>30 marks<\/strong>\n              <\/div>\n\n            <\/div>\n\n          <\/div>\n\n          <div class=\"ols-course-cta-features\">\n\n            <div class=\"ols-course-feature\">\n              <h3>Guided video teaching<\/h3>\n              <p>\n                Learn the chemistry and exam technique through structured video lessons with worked examples and walkthroughs.\n              <\/p>\n            <\/div>\n\n            <div class=\"ols-course-feature\">\n              <h3>Instant MCQ feedback<\/h3>\n              <p>\n                Auto-marked MCQ quizzes provide immediate diagnostic feedback for every answer choice.\n              <\/p>\n            <\/div>\n\n            <div class=\"ols-course-feature\">\n              <h3>Teacher-marked SAQs<\/h3>\n              <p>\n                Submit written exam responses and receive chemistry specialist feedback with improvement guidance.\n              <\/p>\n            <\/div>\n\n            <div class=\"ols-course-feature\">\n              <h3>Progress tracking<\/h3>\n              <p>\n                Identify strengths and weaknesses across the full Topic 4A\/B 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src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Virtual-Lesson.mp4\" muted=\"\" playsinline=\"\" preload=\"auto\">\n                  <\/video>\n                <\/div>\n              <\/div>\n            <\/section>\n          <\/div>\n        <\/section>\n\n        <section id=\"sceneMcq\" class=\"ols-scene\">\n          <div class=\"ols-mcq-stage\">\n            <div id=\"mcqIntroScreen\" class=\"ols-mcq-intro-screen\">\n              <div class=\"ols-mcq-intro-title-wrap\">\n                <h1 class=\"ols-mcq-intro-title\">\n                  <span id=\"mcqIntroTitleText\"><\/span><span id=\"mcqIntroTitleCursor\" class=\"ols-title-cursor\"><\/span>\n                <\/h1>\n              <\/div>\n            <\/div>\n\n            <div class=\"ols-mcq-scale-wrap\">\n              <main id=\"mcqScreen\" class=\"ols-mcq-screen\">\n                <section class=\"mcq-question-area\">\n                  <p class=\"mcq-question-lead\">Some ionic radii are shown.<\/p>\n\n                  <table class=\"mcq-ionic-table\">\n                    <thead>\n                      <tr>\n                        <th>Ion<\/th>\n                        <th>Ionic radius \/ nm<\/th>\n                      <\/tr>\n                    <\/thead>\n                    <tbody>\n                      <tr><td>Na<sup>+<\/sup><\/td><td>0.102<\/td><\/tr>\n                      <tr><td>K<sup>+<\/sup><\/td><td>0.138<\/td><\/tr>\n                      <tr><td>F<sup>\u2212<\/sup><\/td><td>0.133<\/td><\/tr>\n                      <tr><td>Cl<sup>\u2212<\/sup><\/td><td>0.180<\/td><\/tr>\n                    <\/tbody>\n                  <\/table>\n\n                  <p class=\"mcq-question-main\">Which compound has the strongest ionic bonding?<\/p>\n\n                  <div class=\"mcq-options-wrap\">\n                    <div id=\"mcqWrongOption\" class=\"mcq-option-row\">\n                      <span class=\"mcq-radio\"><\/span>\n                      <span class=\"mcq-radio-ripple\"><\/span>\n                      <span class=\"mcq-option-label\">sodium chloride<\/span>\n\n                      <span id=\"mcqSpecificFeedback\" class=\"mcq-specific-feedback\">\n                        <span id=\"mcqCrossIcon\" class=\"mcq-cross-icon\">\u00d7<\/span>\n                        <span class=\"mcq-specific-feedback-text\">\n                          <span id=\"mcqSpecificText\"><\/span><span id=\"mcqSpecificCursor\" class=\"cursor mcq-specific-cursor\" style=\"display:none;\"><\/span>\n                        <\/span>\n                      <\/span>\n                    <\/div>\n\n                    <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">potassium chloride<\/span><\/div>\n                    <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">sodium fluoride<\/span><\/div>\n                    <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">potassium fluoride<\/span><\/div>\n                  <\/div>\n\n                  <button id=\"mcqSubmitButton\" class=\"mcq-submit-button\">Submit answer<\/button>\n                <\/section>\n\n                <section id=\"mcqGeneralFeedback\" class=\"mcq-general-feedback\">\n                  <span id=\"mcqGeneralText\"><\/span><span id=\"mcqGeneralCursor\" class=\"cursor mcq-general-cursor\" style=\"display:none;\"><\/span>\n                <\/section>\n              <\/main>\n            <\/div>\n          <\/div>\n        <\/section>\n\n        <section id=\"sceneSaq\" class=\"ols-scene\">\n          <div class=\"ols-saq-stage\">\n            <div id=\"saqIntro\" class=\"ols-saq-intro\">\n              <div class=\"ols-saq-intro-title-wrap\">\n                <h1 class=\"ols-saq-intro-title\">\n    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Risk<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/isomerism\/\">Isomerism<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">Reactions of Alkanes<\/a>\n        <\/div>\n      <\/section>\n    \n\n      <!-- OLS Author Copyright Footprint \/ Attribution Card -->\n      <section class=\"ols-attribution-card\">\n        <style>\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            font-family: Poppins, Arial, sans-serif;\n            box-sizing: border-box;\n          }\n      \n          .ols-attribution-card,\n          .ols-attribution-card * {\n            box-sizing: border-box;\n          }\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      \n          .ols-attribution-card strong {\n            font-weight: 700;\n            color: #1C244B;\n          }\n      \n          @media (max-width: 760px) {\n            .ols-attribution-card {\n              padding: 24px 18px;\n              border-radius: 22px;\n            }\n          }\n        <\/style>\n      \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. 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