{"id":4839,"date":"2026-06-03T06:24:39","date_gmt":"2026-06-03T05:24:39","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/geometric-isomerism\/"},"modified":"2026-10-25T12:10:55","modified_gmt":"2026-10-25T12:10:55","slug":"geometric-isomerism","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/geometric-isomerism\/","title":{"rendered":"Geometric Isomerism"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-geometric-isomerism-page\">\n  <style>\n    .ols-revision-page {\n      --navy: #1C244B;\n      --blue: #2563eb;\n      --soft-blue: #eef4ff;\n      --soft-red: #fff7f7;\n      --soft-purple: #f7f0ff;\n      --soft-green: #f0f7f1;\n      --gold: #c9973a;\n      --grey-text: #667085;\n      --body-text: #1f2937;\n      --border: rgba(28, 36, 75, 0.14);\n     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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\/alkenes\/\">Alkenes<\/a> \/\n        <span>Geometric Isomerism<\/span>\n      <\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Geometric Isomerism<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to stereoisomerism in alkenes, restricted rotation around C=C bonds, E-Z naming, priority groups and the link between E-Z and cis-trans isomerism.<\/p>\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<!-- Copyright (c) 2026 Dr. Mohammed Al-Fatah, onlinelearningsystem.net. 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border:1px solid rgba(28,36,75,0.18);\n}\n.ols-ezrt-001 .ezrt-key i.k-ball{border-radius:50%;}\n\n@media (max-width:760px){\n  .ols-ezrt-001{padding:26px; border-radius:22px;}\n  .ols-ezrt-001 h2.ezrt-title{font-size:20.5px;}\n  .ols-ezrt-001 p.ezrt-sub{font-size:13.5px;}\n  .ols-ezrt-001 .ezrt-stage{height:400px;}\n  .ols-ezrt-001 .ezrt-rowlab{min-width:100%;}\n  .ols-ezrt-001 .ezrt-seg button{padding:9px 13px; font-size:13px;}\n  .ols-ezrt-001 .ezrt-lab{font-size:10.5px; padding:4px 8px;}\n  .ols-ezrt-001 .ezrt-lab.l-part{font-size:9.5px; padding:3px 7px;}\n  .ols-ezrt-001 .ezrt-lab.l-read{font-size:12px; padding:5px 9px;}\n  .ols-ezrt-001 .ezrt-caption{font-size:10.5px; padding:5px 9px; max-width:64%;}\n  .ols-ezrt-001 .ezrt-badge{font-size:10.5px; padding:4px 9px;}\n  .ols-ezrt-001 .ezrt-badge.b-eq{font-size:11px;}\n  .ols-ezrt-001 .ezrt-badges{max-width:calc(100% - 28px);}\n  .ols-ezrt-001 .ezrt-info{padding:18px;}\n}\n\/* on a phone the caption needs the full top row, so the drag hint goes *\/\n@media (max-width:480px){\n  .ols-ezrt-001 .ezrt-hint{display:none;}\n  .ols-ezrt-001 .ezrt-caption{max-width:calc(100% - 28px);}\n}\n@media (prefers-reduced-motion:reduce){\n  .ols-ezrt-001 .ezrt-seg button,.ols-ezrt-001 .ezrt-pill{transition:none;}\n}\n\n.ols-cc-ezrt-001{\n  font-family:'Poppins',system-ui,-apple-system,'Segoe UI',Roboto,Helvetica,Arial,sans-serif;\n  margin:10px auto 0; text-align:center; font-size:11px; font-style:italic; color:#aab0c0;\n}\n.ols-cc-ezrt-001 a{color:#aab0c0; text-decoration:none;}\n.ols-cc-ezrt-001 a:hover{text-decoration:underline;}\n.ols-ezrt-001 .ezrt-seg button{display:inline-flex; align-items:center;}\n.ols-ezrt-001 .ezrt-seg button .ezrt-n{display:inline-flex; align-items:center; justify-content:center; width:20px; height:20px; margin-right:9px; border-radius:50%; font-size:11px; font-weight:600; background:rgba(37,99,235,0.10); color:#2563eb; flex:0 0 auto;}\n.ols-ezrt-001 .ezrt-seg button[aria-pressed=\"true\"] .ezrt-n{background:#ffffff; color:#2563eb;}\n<\/style>\n\n<div class=\"ezrt-head\">\n  <h2 class=\"ezrt-title\">Free and Restricted Rotation: Why E\/Z Isomers Exist<\/h2>\n  <p class=\"ezrt-sub\">Choose a step to watch butane turn freely about its C\u2013C \u03c3 bond, then see how the \u03c0 bond locks but-2-ene into separate Z and E isomers.<\/p>\n<\/div>\n\n<div class=\"ezrt-stage\" id=\"ezrtStage\">\n  <canvas class=\"ezrt-canvas\" id=\"ezrtCanvas\"><\/canvas>\n  <div class=\"ezrt-overlay\" id=\"ezrtOverlay\"><\/div>\n  <div class=\"ezrt-caption\" id=\"ezrtCaption\"><\/div>\n  <div class=\"ezrt-hint\" id=\"ezrtHint\">Drag to rotate<\/div>\n  <div class=\"ezrt-badges\" id=\"ezrtBadges\"><\/div>\n<\/div>\n\n<div class=\"ezrt-controls\">\n  <div class=\"ezrt-row\">\n    <span class=\"ezrt-rowlab\">Step<\/span>\n    <div class=\"ezrt-seg\" role=\"group\" aria-label=\"Step\">\n      <button type=\"button\" data-step=\"1\" aria-pressed=\"true\"><span class=\"ezrt-n\">1<\/span>Free rotation in butane<\/button>\n      <button type=\"button\" data-step=\"2\" aria-pressed=\"false\"><span class=\"ezrt-n\">2<\/span>The \u03c0 bond locks C=C<\/button>\n      <button type=\"button\" data-step=\"3\" aria-pressed=\"false\"><span class=\"ezrt-n\">3<\/span>Z isomer<\/button>\n      <button type=\"button\" data-step=\"4\" aria-pressed=\"false\"><span class=\"ezrt-n\">4<\/span>E isomer<\/button>\n      <button type=\"button\" data-step=\"5\" aria-pressed=\"false\"><span class=\"ezrt-n\">5<\/span>Breaking the \u03c0 bond<\/button>\n    <\/div>\n  <\/div>\n\n  <div class=\"ezrt-row\">\n    <span class=\"ezrt-rowlab\">View<\/span>\n    <button type=\"button\" class=\"ezrt-pill\" id=\"ezrtResetV\">Reset view<\/button>\n  <\/div>\n<\/div>\n\n<div class=\"ezrt-info\">\n  <h3 id=\"ezrtInfoTitle\"><\/h3>\n  <p id=\"ezrtInfoText\"><\/p>\n  <div class=\"ezrt-facts\" id=\"ezrtFacts\"><\/div>\n  <div class=\"ezrt-key\">\n    <span><i class=\"k-ball\" style=\"background:#464a54\"><\/i>Carbon<\/span>\n    <span><i class=\"k-ball\" style=\"background:#ececf0\"><\/i>Hydrogen<\/span>\n    <span><i class=\"\" style=\"background:rgba(70,120,215,0.6)\"><\/i>sp\u00b3 hybrid orbital<\/span>\n    <span><i class=\"\" style=\"background:rgba(236,140,40,0.6)\"><\/i>p orbital<\/span>\n    <span><i class=\"\" style=\"background:rgba(226,150,30,0.6)\"><\/i>\u03c3 molecular orbital (replaces two orbitals)<\/span>\n    <span><i class=\"\" style=\"background:rgba(22,150,175,0.6)\"><\/i>\u03c0 molecular orbital (replaces two p orbitals)<\/span>\n    <span><i class=\"k-ball\" style=\"background:rgba(214,150,24,0.9)\"><\/i>Higher-priority group (CH\u2083)<\/span>\n  <\/div>\n<\/div>\n\n<script src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/JS\/ez-rotation.js?v=20261025p\"><\/script>\n<\/section>\n\n<p class=\"ols-cc-ezrt-001\">&copy; Dr. Mohammed Al-Fatah &#8211; <a href=\"https:\/\/www.onlinelearningsystem.net\" target=\"_blank\" rel=\"noopener\">onlinelearningsystem.net<\/a><\/p>\n\n\n      <article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">1<\/div>\n<h2>Before You Start<\/h2>\n<\/div>\n<p>This page builds on alkene bonding and on structural isomers.<\/p>\n<ul class=\"ols-list\">\n<li>An alkene contains a C=C double bond made of one \u03c3 bond and one \u03c0 bond.<\/li>\n<li>Structural isomers have the same molecular formula but atoms joined in a different order.<\/li>\n<li>Atoms around each C=C carbon lie in one plane at about 120\u00b0.<\/li>\n<li>Atomic number increases across and down the Periodic Table: Cl (17) beats C (6) and H (1).<\/li>\n<\/ul>\n<\/article>\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: Isomers and Atomic Number<\/h2>\n<p>Four quick GCSE questions on isomers, alkene formulae and atomic number before you meet stereoisomers.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"1267\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">2<\/div><h2>What Are Stereoisomers?<\/h2><\/div>\n        <p><strong>Stereoisomers<\/strong> are compounds with the same structural formula but a different three-dimensional arrangement of atoms in space.<\/p>\n        <p>In alkenes, this matters because the <strong>C=C double bond restricts rotation<\/strong>. The atoms or groups attached to the double bond cannot freely rotate into a new arrangement without breaking the pi bond.<\/p>\n        <p>This produces a type of stereoisomerism called <strong>E-Z stereoisomerism<\/strong>, also called geometric isomerism.<\/p>\n        <div class=\"ols-key-box\"><p><strong>Key idea:<\/strong> E-Z isomers are not structural isomers. They have the same connectivity, but different spatial arrangement around the carbon-carbon double bond.<\/p><\/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: Structural Isomer or Stereoisomer?<\/h2>\n<p>Complete a comparison of three alkenes that are not on this page.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-17\" class=\"h5p-iframe\" data-content-id=\"17\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Geometric Isomerism Drag: Comparing the Pentenes\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">3<\/div><h2>Why E-Z Isomerism Occurs<\/h2><\/div>\n        <p>E-Z isomerism occurs because the carbon-carbon double bond contains a <strong>pi bond<\/strong>. Rotation around the C=C bond is restricted because rotating one carbon would break the sideways overlap of the p orbitals.<\/p>\n        <p>By contrast, a carbon-carbon single bond can rotate freely. This is why simple alkanes do not usually produce this type of fixed geometric arrangement.<\/p>\n        <div class=\"ols-key-box\"><p><strong>Exam focus:<\/strong> Always link E-Z isomerism to <strong>restricted rotation around the C=C double bond<\/strong>.<\/p><\/div>\n        <div class=\"ols-figure-card ols-zoom-pop\">\n          <div class=\"ols-figure-image\">\n            <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-mv-12-displayed.svg\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-mv-12-displayed.svg\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-mv-12-displayed.svg\" alt=\"Displayed formulae of (Z)-but-2-ene, (E)-but-2-ene\" width=\"1514\" height=\"1071\"><\/a>\n          <\/div>\n        <\/div>\n        \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: Explain Two Forms Against One<\/h2>\n<p>Write a short explanation, then compare it with the mark points and the model answer.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-18\" class=\"h5p-iframe\" data-content-id=\"18\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Geometric Isomerism Explain: 1,2-Dibromoethene and 1,2-Dibromoethane\"><\/iframe><\/div><\/div>\n<\/section>\n\n\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">4<\/div><h2>Conditions for E-Z Stereoisomerism<\/h2><\/div>\n        <p>For an alkene to show E-Z stereoisomerism, <strong>two conditions<\/strong> must both be met:<\/p>\n        <ol>\n          <li>There must be <strong>restricted rotation<\/strong> about the carbon-carbon double bond.<\/li>\n          <li>Each carbon atom of the C=C bond must be attached to <strong>two different atoms or groups<\/strong>.<\/li>\n        <\/ol>\n        <p>If either carbon in the C=C bond has two identical groups attached, E-Z isomerism is not possible.<\/p>\n        <div class=\"ols-figure-card ols-zoom-pop\">\n          <div class=\"ols-figure-image\">\n            <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-cd-15-butene1noez.svg\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-cd-15-butene1noez.svg\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-cd-15-butene1noez.svg\" alt=\"But-1-ene with the two hydrogen atoms on carbon 1 ringed: identical groups, so no E\/Z isomers\" width=\"1518\" height=\"946\"><\/a>\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-68-ezcheck.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-68-ezcheck.jpg\" alt=\"Checklist for E\/Z isomerism: restricted rotation and two different groups per carbon, tested on four alkenes\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-img-68-ezcheck.jpg\">\n<\/a>\n<\/div>\n<div class=\"ols-figure-caption\"><p>E\/Z isomers need restricted rotation and two different groups on each carbon of the C=C.<\/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: Which Alkenes Show E-Z Isomerism?<\/h2>\n<p>Sketch each alkene, then click every one that has E and Z isomers.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-297\" class=\"h5p-iframe\" data-content-id=\"297\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Geometric Isomerism Mark the Words: Which Alkenes Show E-Z Isomerism\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">5<\/div><h2>Assigning E and Z<\/h2><\/div>\n        <p>To name an alkene with E-Z stereoisomerism, first identify the <strong>priority group<\/strong> on each carbon atom of the double bond.<\/p>\n        <p>The priority group is found by comparing the atoms directly attached to each double-bond carbon. The atom with the <strong>higher atomic number<\/strong> has higher priority.<\/p>\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Arrangement of priority groups<\/th>\n                <th>Name used<\/th>\n                <th>Memory aid<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td>Priority groups on the same side of the C=C bond<\/td>\n                <td><strong>Z<\/strong><\/td>\n                <td><strong>Z<\/strong> comes from <em>zusammen<\/em>, meaning together.<\/td>\n              <\/tr>\n              <tr>\n                <td>Priority groups on opposite sides of the C=C bond<\/td>\n                <td><strong>E<\/strong><\/td>\n                <td><strong>E<\/strong> comes from <em>entgegen<\/em>, meaning opposite.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n        <div class=\"ols-figure-card ols-zoom-pop\">\n          <div class=\"ols-figure-image\">\n            <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-cd-16-dichloroethene.svg\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-cd-16-dichloroethene.svg\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-cd-16-dichloroethene.svg\" alt=\"(Z)- and (E)-1,2-dichloroethene with Cl marked as the priority group on each carbon\" width=\"1520\" height=\"1054\"><\/a>\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-69-ezcistrans.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-69-ezcistrans.jpg\" alt=\"Priority by atomic number, Z together and E opposite, and cis\u2013trans as the special case for but-2-ene\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-img-69-ezcistrans.jpg\">\n<\/a>\n<\/div>\n<div class=\"ols-figure-caption\"><p>The higher atomic number on each carbon is the priority group: same side Z, opposite sides E.<\/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: E, Z or Neither?<\/h2>\n<p>Find the priority group on each carbon atom, then decide quickly.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-20\" class=\"h5p-iframe\" data-content-id=\"20\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Geometric Isomerism Quick-Fire: E, Z or Neither\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">6<\/div><h2>Cis-Trans Isomerism<\/h2><\/div>\n        <p><strong>Cis-trans isomerism<\/strong> is a simpler special case of E-Z isomerism. It can be used when two of the substituent groups attached to the double bond are identical.<\/p>\n        <p>For but-2-ene, the two CH<sub>3<\/sub> groups can be on the same side or on opposite sides of the double bond.<\/p>\n        <div class=\"ols-comparison-grid\">\n          <div class=\"ols-mini-card ols-zoom-pop\">\n            <div class=\"ols-mini-card-image\">\n              <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/skel-P008-z-but-2-ene.svg\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/skel-P008-z-but-2-ene.svg\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/skel-P008-z-but-2-ene.svg\" alt=\"Displayed formula of (Z)-but-2-ene, with both CH3 groups on the same side of the C=C double bond\"><\/a>\n            <\/div>\n            <div class=\"ols-mini-card-body\">\n              <h3>Z-but-2-ene<\/h3>\n              <p>The two CH<sub>3<\/sub> groups are on the same side, so this can also be called <strong>cis-but-2-ene<\/strong>.<\/p>\n            <\/div>\n          <\/div>\n          <div class=\"ols-mini-card ols-zoom-pop\">\n            <div class=\"ols-mini-card-image\">\n              <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/skel-26-e-but-2-ene-callouts.svg\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-cd-14-zebutene.svg\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-cd-14-zebutene.svg\" alt=\"(Z)- and (E)-but-2-ene side by side with the CH\u2083 groups ringed and the C=C axis dashed\"><\/a>\n            <\/div>\n            <div class=\"ols-mini-card-body\">\n              <h3>E-but-2-ene<\/h3>\n              <p>The two CH<sub>3<\/sub> groups are on opposite sides, so this can also be called <strong>trans-but-2-ene<\/strong>.<\/p>\n            <\/div>\n          <\/div>\n        <\/div>\n        <div class=\"ols-key-box\"><p><strong>Important:<\/strong> E-Z notation is the more general and accurate naming system, especially when the groups attached to the C=C bond are not identical.<\/p><\/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: Pick the Accurate Statement<\/h2>\n<p>Each round puts a common mistake next to the correct idea, in a molecule you have not met on this page.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-19\" class=\"h5p-iframe\" data-content-id=\"19\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Geometric Isomerism Summary: Misconceptions in New Molecules\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">7<\/div><h2>Common Exam Mistakes<\/h2><\/div>\n        <ul>\n          <li>Do not call E-Z isomers <strong>structural isomers<\/strong>. They have the same structural formula.<\/li>\n          <li>Do not assign E or Z by only looking at the largest group visually. Use <strong>atomic number priority<\/strong>.<\/li>\n          <li>Do not assume every alkene shows E-Z isomerism. Each carbon in the C=C bond must have two different groups attached.<\/li>\n          <li>Do not say the molecule rotates around the double bond. The whole point is that rotation around C=C is restricted.<\/li>\n        <\/ul>\n      <\/article>\n\n      \n\n      <section class=\"ols-infographic-full\" aria-label=\"Geometric isomerism infographic summary\">\n        <div class=\"ols-infographic-full-frame\">\n          <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/skel-02-geometric-isomerism-a.svg\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/skel-02-geometric-isomerism-a.svg\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/skel-02-geometric-isomerism-a.svg\" alt=\"Geometric isomerism: definition, conditions, and the Z and E isomers of but-2-ene\" width=\"1410\" height=\"963\"><\/a>\n          <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/skel-02-geometric-isomerism-b.svg\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/skel-02-geometric-isomerism-b.svg\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/skel-02-geometric-isomerism-b.svg\" alt=\"CIP priority rule applied to Z- and E-1,2-dichloroethene, and but-1-ene which has no E\/Z isomers\" width=\"1501\" height=\"1175\"><\/a>\n          <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/skel-02-geometric-isomerism-c.svg\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/skel-02-geometric-isomerism-c.svg\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/skel-02-geometric-isomerism-c.svg\" alt=\"How cis and trans relate to Z and E, with a short exam recap\" width=\"1502\" height=\"1011\"><\/a>\n        <\/div>\n      <\/section>\n\n<section class=\"ols-faq-card\">\n        <h2>FAQs<\/h2>\n        <p>These questions cover the E-Z decisions students most often get wrong.<\/p>\n        <div class=\"ols-faq-list\">\n          <div class=\"ols-faq-item\">\n            <h3>Does but-1-ene have E-Z isomers?<\/h3>\n            <p>No. Carbon 1 carries two hydrogen atoms, so swapping them gives the same molecule. Each C=C carbon needs two different groups.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Do I compare the whole group or the first atom?<\/h3>\n            <p>Compare the atoms bonded directly to the C=C carbon first. The one with the higher atomic number has priority; look further along only if they tie.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Is Z always the same as cis?<\/h3>\n            <p>Not always. They agree when the same group sits on each carbon, as in but-2-ene, but can differ when the priority groups are not the ones being called cis.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Are E-Z isomers structural isomers?<\/h3>\n            <p>No. They are stereoisomers: same structural formula, different arrangement in space.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why do alkanes not show E-Z isomerism?<\/h3>\n            <p>A C-C single bond can rotate freely, so any arrangement turns into any other. Only the \u03c0 bond of a C=C bond locks the groups in place.<\/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        View LinkedIn Profile\n      <\/a>\n\n    <\/div>\n\n  <\/div>\n\n\n<section class=\"ols-related-card\">\n        <h2>Related Alkene Revision Notes<\/h2>\n        <p>Continue through Topic 6 by linking geometric isomerism to alkene bonding, electrophilic addition and polymerisation.<\/p>\n        <div class=\"ols-related-grid\">\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/alkene-bonding\/\">Alkene Bonding<\/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\/electrophilic-addition-mechanism\/\">Electrophilic Addition Mechanism<\/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\/reactions-of-alkenes\/\">Reactions of Alkenes<\/a>\n        <\/div>\n      <\/section>\n\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>\n(function(){\n  function ensureCss(){\n    if(document.getElementById(\"olsGeoFullscreenCss001\")){\n      return;\n    }\n    var css = document.createElement(\"style\");\n    css.id = \"olsGeoFullscreenCss001\";\n    css.textContent = \".ols-image-lightbox{position:fixed;inset:0;z-index:2147483647;display:none;align-items:center;justify-content:center;padding:28px;background:rgba(8,12,30,.88);cursor:zoom-out}.ols-image-lightbox.is-visible{display:flex!important}.ols-image-lightbox img{display:block;max-width:96vw;max-height:92vh;width:auto;height:auto;object-fit:contain;border-radius:18px;background:#fff;box-shadow:0 28px 90px rgba(0,0,0,.42)}.ols-image-lightbox-close{position:fixed;top:18px;right:18px;z-index:2147483647;width:44px;height:44px;border:0;border-radius:999px;background:#fff;color:#1C244B;font-size:28px;line-height:1;font-weight:700;cursor:pointer;box-shadow:0 12px 30px rgba(0,0,0,.25)}\";\n    document.head.appendChild(css);\n  }\n\n  var lightbox;\n  var lightboxImage;\n  var closeButton;\n\n  function closeLightbox(){\n    if(!lightbox){\n      return false;\n    }\n    lightbox.classList.remove(\"is-visible\");\n    if(lightboxImage){\n      lightboxImage.removeAttribute(\"src\");\n    }\n    document.documentElement.style.overflow = \"\";\n    document.body.style.overflow = \"\";\n    return false;\n  }\n\n  function ensureLightbox(){\n    ensureCss();\n    if(lightbox){\n      return;\n    }\n    lightbox = document.createElement(\"div\");\n    lightbox.className = \"ols-image-lightbox\";\n    lightbox.setAttribute(\"role\", \"dialog\");\n    lightbox.setAttribute(\"aria-modal\", \"true\");\n    lightbox.setAttribute(\"aria-label\", \"Fullscreen image preview\");\n\n    closeButton = document.createElement(\"button\");\n    closeButton.className = \"ols-image-lightbox-close\";\n    closeButton.type = \"button\";\n    closeButton.setAttribute(\"aria-label\", \"Close fullscreen image\");\n    closeButton.textContent = \"\u00d7\";\n\n    lightboxImage = document.createElement(\"img\");\n    lightboxImage.alt = \"\";\n\n    lightbox.appendChild(closeButton);\n    lightbox.appendChild(lightboxImage);\n    document.body.appendChild(lightbox);\n\n    lightbox.addEventListener(\"click\", function(event){\n      if(event.target === lightbox){\n        closeLightbox();\n      }\n    });\n\n    closeButton.addEventListener(\"click\", function(event){\n      event.preventDefault();\n      event.stopPropagation();\n      closeLightbox();\n    });\n  }\n\n  function openSrc(src, altText){\n    if(!src){\n      return true;\n    }\n    ensureLightbox();\n    lightboxImage.src = src;\n    lightboxImage.alt = altText || \"Fullscreen revision image\";\n    lightbox.classList.add(\"is-visible\");\n    document.documentElement.style.overflow = \"hidden\";\n    document.body.style.overflow = \"hidden\";\n    return false;\n  }\n\n  window.olsGeoFull = function(linkOrImage){\n    var node = linkOrImage;\n    var img = null;\n    var src = \"\";\n    var altText = \"Fullscreen revision image\";\n\n    if(node){\n      if(node.tagName){\n        if(node.tagName.toLowerCase() === \"a\"){\n          img = node.querySelector(\"img[data-fullscreen-src]\");\n          src = node.getAttribute(\"href\") || \"\";\n        }\n        if(node.tagName.toLowerCase() === \"img\"){\n          img = node;\n        }\n      }\n    }\n\n    if(img){\n      src = img.getAttribute(\"data-fullscreen-src\") || img.currentSrc || img.src || src;\n      altText = img.getAttribute(\"alt\") || img.getAttribute(\"aria-label\") || altText;\n    }\n\n    return openSrc(src, altText);\n  };\n\n  function prepareAllImages(){\n    var selector = \".ols-figure-card.ols-zoom-pop .ols-figure-image img[data-fullscreen-src], .ols-mini-card.ols-zoom-pop .ols-mini-card-image img[data-fullscreen-src], .ols-infographic-full-frame img[data-fullscreen-src]\";\n    var list = document.querySelectorAll(selector);\n    for(var i = 0; i < list.length; i++){\n      var item = list[i];\n      item.style.cursor = \"zoom-in\";\n      item.setAttribute(\"tabindex\", \"0\");\n      item.setAttribute(\"role\", \"button\");\n      var label = item.getAttribute(\"alt\") || item.getAttribute(\"aria-label\") || \"Revision image\";\n      item.setAttribute(\"aria-label\", label + \". 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Each C=C carbon needs two different groups.\"\n                    }\n                },\n                {\n                    \"@type\": \"Question\",\n                    \"name\": \"Do I compare the whole group or the first atom?\",\n                    \"acceptedAnswer\": {\n                        \"@type\": \"Answer\",\n                        \"text\": \"Compare the atoms bonded directly to the C=C carbon first. The one with the higher atomic number has priority; look further along only if they tie.\"\n                    }\n                },\n                {\n                    \"@type\": \"Question\",\n                    \"name\": \"Is Z always the same as cis?\",\n                    \"acceptedAnswer\": {\n                        \"@type\": \"Answer\",\n                        \"text\": \"Not always. 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