{"id":4840,"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\/electrophilic-addition-mechanism\/"},"modified":"2026-10-25T12:10:21","modified_gmt":"2026-10-25T12:10:21","slug":"electrophilic-addition-mechanism","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/electrophilic-addition-mechanism\/","title":{"rendered":"Electrophilic Addition Mechanism"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-electrophilic-addition-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      --grey-text: #667085;\n      --body-text: #1f2937;\n      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border-radius: 22px;\n      }\n\n      .ols-author {\n        flex-direction: column;\n        align-items: flex-start;\n        padding: 22px;\n      }\n\n      .ols-note-title {\n        align-items: flex-start;\n      }\n\n      .ols-figure-card {\n        border-radius: 22px;\n      }\n\n      .ols-figure-image {\n        min-height: 250px;\n        padding: 14px;\n      }\n\n      .ols-figure-caption {\n        padding: 18px;\n      }\n\n      .ols-related-grid {\n        grid-template-columns: 1fr;\n      }\n\n      .ols-infographic-full {\n        max-width: 100%;\n        margin: 0 auto 28px;\n      }\n\n      .ols-infographic-full-frame {\n        border-radius: 18px;\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    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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>Electrophilic Addition Mechanism<\/span>\n    <\/nav>\n\n    <header class=\"ols-title-card\">\n      <h1>Electrophilic Addition Mechanism<\/h1>\n      <p class=\"ols-page-intro\">A concise revision guide to addition reactions of alkenes, electrophiles, electron-rich \u03c0 bonds and why the carbon-carbon double bond is the reactive centre in alkene chemistry.<\/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<!-- 3D card: electrophilic-addition-ethene (5 Oct 2026, Topics 1-5 upgrade) -->\n<!-- Copyright (c) 2026 Dr. Mohammed Al-Fatah, onlinelearningsystem.net. 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color:#2563eb; flex:0 0 auto;}\n.ols-eae-001 .eae-seg button[aria-pressed=\"true\"] .eae-n{background:#ffffff; color:#2563eb;}\n<\/style>\n\n<div class=\"eae-head\">\n  <h2 class=\"eae-title\">Electrophilic Addition in Motion<\/h2>\n  <p class=\"eae-sub\">Choose a step to watch HBr and then Br\u2082 add across the \u03c0 bond of ethene, one curly arrow at a time.<\/p>\n<\/div>\n\n<div class=\"eae-stage\" id=\"eaeStage\">\n  <canvas class=\"eae-canvas\" id=\"eaeCanvas\"><\/canvas>\n  <div class=\"eae-overlay\" id=\"eaeOverlay\"><\/div>\n  <div class=\"eae-caption\" id=\"eaeCaption\"><\/div>\n  <div class=\"eae-hint\" id=\"eaeHint\">Drag to rotate<\/div>\n  <div class=\"eae-badges\" id=\"eaeBadges\"><\/div>\n<\/div>\n\n<div class=\"eae-controls\">\n  <div class=\"eae-row\">\n    <span class=\"eae-rowlab\">Step<\/span>\n    <div class=\"eae-seg\" role=\"group\" aria-label=\"Step\">\n      <button type=\"button\" data-step=\"1\" aria-pressed=\"true\"><span class=\"eae-n\">1<\/span>HBr meets the \u03c0 bond<\/button>\n      <button type=\"button\" data-step=\"2\" aria-pressed=\"false\"><span class=\"eae-n\">2<\/span>The \u03c0 bond attacks H\u03b4+<\/button>\n      <button type=\"button\" data-step=\"3\" aria-pressed=\"false\"><span class=\"eae-n\">3<\/span>Br\u207b attacks the carbocation<\/button>\n      <button type=\"button\" data-step=\"4\" aria-pressed=\"false\"><span class=\"eae-n\">4<\/span>Bromine is polarised<\/button>\n      <button type=\"button\" data-step=\"5\" aria-pressed=\"false\"><span class=\"eae-n\">5<\/span>Bromine adds<\/button>\n    <\/div>\n  <\/div>\n\n  <div class=\"eae-row\">\n    <span class=\"eae-rowlab\">View<\/span>\n    <button type=\"button\" class=\"eae-pill\" id=\"eaeResetV\">Reset view<\/button>\n  <\/div>\n<\/div>\n\n<div class=\"eae-info\">\n  <h3 id=\"eaeInfoTitle\"><\/h3>\n  <p id=\"eaeInfoText\"><\/p>\n  <div class=\"eae-facts\" id=\"eaeFacts\"><\/div>\n  <div class=\"eae-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=\"k-ball\" style=\"background:#8c3222\"><\/i>Bromine<\/span>\n    <span><i class=\"k-ball\" style=\"background:#f6c426\"><\/i>Electron<\/span>\n    <span><i class=\"k-ball\" style=\"background:#b4cbe6\"><\/i>\u03c0 bond<\/span>\n    <span><i class=\"k-ball\" style=\"background:#f3e2b4\"><\/i>Empty p orbital<\/span>\n  <\/div>\n<\/div>\n\n<script src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/JS\/electrophilic-addition-ethene.js?v=20261025p\"><\/script>\n<\/section>\n\n<p class=\"ols-cc-eae-001\">&copy; Dr. Mohammed Al-Fatah &#8211; <a href=\"https:\/\/www.onlinelearningsystem.net\" target=\"_blank\" rel=\"noopener\">onlinelearningsystem.net<\/a><\/p>\n\n\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: What Alkenes Do<\/h2>\n<p>Three quick questions on the reactions of alkenes that you met at GCSE.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"735\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n      <div class=\"ols-note-title\"><div class=\"ols-note-icon\">1<\/div><h2>Addition Reactions of Alkenes<\/h2><\/div>\n      <p>An <strong>addition reaction<\/strong> is a reaction in which two reactant molecules combine to form a single product molecule.<\/p>\n      <p>Alkenes commonly undergo addition reactions because their <strong>carbon-carbon double bond<\/strong> can be broken and replaced by new single bonds.<\/p>\n      <p>This is why the C=C bond is the functional group that controls the characteristic reactions of alkenes.<\/p>\n      <div class=\"ols-key-box\"><p><strong>Key idea:<\/strong> In an alkene addition reaction, atoms add across the C=C double bond and only one organic product molecule is formed.<\/p><\/div>\n      <div class=\"ols-figure-card\">\n        <div class=\"ols-figure-image\" role=\"img\" aria-label=\"Addition reaction diagram showing an alkene double bond opening to form a saturated product\">\n          <svg viewBox=\"0 0 900 360\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\">\n            <rect width=\"900\" height=\"360\" rx=\"28\" fill=\"#ffffff\"><\/rect>\n            <rect x=\"38\" y=\"42\" width=\"260\" height=\"236\" rx=\"24\" fill=\"#eef4ff\" stroke=\"#d8e5ff\"><\/rect>\n            <rect x=\"600\" y=\"42\" width=\"260\" height=\"236\" rx=\"24\" fill=\"#fff7f7\" stroke=\"#f4dada\"><\/rect>\n            <text x=\"168\" y=\"88\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"26\" font-weight=\"800\" fill=\"#1C244B\">Alkene<\/text>\n            <text x=\"730\" y=\"88\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"26\" font-weight=\"800\" fill=\"#1C244B\">Addition product<\/text>\n            <line x1=\"118\" y1=\"166\" x2=\"218\" y2=\"166\" stroke=\"#1C244B\" stroke-width=\"10\" stroke-linecap=\"round\"><\/line>\n            <line x1=\"118\" y1=\"188\" x2=\"218\" y2=\"188\" stroke=\"#2563eb\" stroke-width=\"10\" stroke-linecap=\"round\"><\/line>\n            <text x=\"168\" y=\"235\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"28\" font-weight=\"700\" fill=\"#1C244B\">C=C<\/text>\n            <line x1=\"365\" y1=\"176\" x2=\"535\" y2=\"176\" stroke=\"#1C244B\" stroke-width=\"6\" stroke-linecap=\"round\"><\/line>\n            <polygon points=\"535,176 510,160 510,192\" fill=\"#1C244B\"><\/polygon>\n            <text x=\"450\" y=\"138\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"23\" font-weight=\"700\" fill=\"#2563eb\">two reactants<\/text>\n            <text x=\"450\" y=\"225\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"23\" font-weight=\"700\" fill=\"#2563eb\">one product<\/text>\n            <line x1=\"680\" y1=\"176\" x2=\"780\" y2=\"176\" stroke=\"#1C244B\" stroke-width=\"10\" stroke-linecap=\"round\"><\/line>\n            <circle cx=\"660\" cy=\"176\" r=\"22\" fill=\"#2563eb\"><\/circle>\n            <circle cx=\"800\" cy=\"176\" r=\"22\" fill=\"#2563eb\"><\/circle>\n            <text x=\"660\" y=\"184\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"18\" font-weight=\"800\" fill=\"#ffffff\">X<\/text>\n            <text x=\"800\" y=\"184\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"18\" font-weight=\"800\" fill=\"#ffffff\">Y<\/text>\n            <text x=\"730\" y=\"235\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"25\" font-weight=\"700\" fill=\"#1C244B\">new single bonds<\/text>\n          <\/svg>\n        <\/div>\n        <div class=\"ols-figure-caption\">\n          <h3>Addition across a double bond<\/h3>\n          <p>The double bond opens up, allowing new atoms or groups to attach to the two carbon atoms from the original C=C bond.<\/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: Addition or Not?<\/h2>\n<p>Decide quickly whether each equation shows an addition reaction.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-24\" class=\"h5p-iframe\" data-content-id=\"24\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Electrophilic Addition Quick-Fire: Addition or Not Addition\"><\/iframe><\/div><\/div>\n<\/section>\n\n    <article class=\"ols-note-card\">\n      <div class=\"ols-note-title\"><div class=\"ols-note-icon\">2<\/div><h2>Why the \u03c0 Bond Reacts<\/h2><\/div>\n      <p>In an alkene, the <strong>\u03c0 bond is weaker than the \u03c3 bond<\/strong>, so it requires less energy to break during a reaction.<\/p>\n      <p>The \u03c0 bond also contains a region of <strong>high electron density<\/strong>. This exposed electron density is especially attractive to electron-seeking species.<\/p>\n      <p>Because the \u03c0 bond is both weaker and more exposed than a \u03c3 bond, it is particularly susceptible to attack by electrophiles.<\/p>\n      <div class=\"ols-key-box\"><p><strong>Exam focus:<\/strong> Link alkene reactivity to the exposed, electron-rich \u03c0 bond rather than simply saying that alkenes have a double bond.<\/p><\/div>\n      <div class=\"ols-figure-card\">\n        <div class=\"ols-figure-image\" role=\"img\" aria-label=\"Pi bond electron density diagram showing electron-rich regions above and below the carbon-carbon bond\">\n          <svg viewBox=\"0 0 900 390\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\">\n            <rect width=\"900\" height=\"390\" rx=\"28\" fill=\"#ffffff\"><\/rect>\n            <ellipse cx=\"450\" cy=\"124\" rx=\"250\" ry=\"62\" fill=\"#2563eb\" opacity=\"0.18\"><\/ellipse>\n            <ellipse cx=\"450\" cy=\"266\" rx=\"250\" ry=\"62\" fill=\"#2563eb\" opacity=\"0.18\"><\/ellipse>\n            <ellipse cx=\"450\" cy=\"124\" rx=\"172\" ry=\"42\" fill=\"#2563eb\" opacity=\"0.26\"><\/ellipse>\n            <ellipse cx=\"450\" cy=\"266\" rx=\"172\" ry=\"42\" fill=\"#2563eb\" opacity=\"0.26\"><\/ellipse>\n            <circle cx=\"355\" cy=\"195\" r=\"40\" fill=\"#1C244B\"><\/circle>\n            <circle cx=\"545\" cy=\"195\" r=\"40\" fill=\"#1C244B\"><\/circle>\n            <text x=\"355\" y=\"205\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"30\" font-weight=\"800\" fill=\"#ffffff\">C<\/text>\n            <text x=\"545\" y=\"205\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"30\" font-weight=\"800\" fill=\"#ffffff\">C<\/text>\n            <line x1=\"395\" y1=\"183\" x2=\"505\" y2=\"183\" stroke=\"#1C244B\" stroke-width=\"10\" stroke-linecap=\"round\"><\/line>\n            <line x1=\"395\" y1=\"207\" x2=\"505\" y2=\"207\" stroke=\"#2563eb\" stroke-width=\"10\" stroke-linecap=\"round\"><\/line>\n            <text x=\"450\" y=\"60\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"28\" font-weight=\"800\" fill=\"#1C244B\">exposed \u03c0 electron density<\/text>\n            <text x=\"450\" y=\"350\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"24\" font-weight=\"700\" fill=\"#667085\">weaker than the \u03c3 bond and easier to break<\/text>\n            <path d=\"M712 112 C660 126, 632 154, 602 180\" fill=\"none\" stroke=\"#c81e1e\" stroke-width=\"6\" stroke-linecap=\"round\"><\/path>\n            <polygon points=\"602,180 612,154 626,177\" fill=\"#c81e1e\"><\/polygon>\n            <text x=\"744\" y=\"105\" font-family=\"Poppins, Arial\" font-size=\"22\" font-weight=\"800\" fill=\"#c81e1e\">E\u207a<\/text>\n          <\/svg>\n        <\/div>\n        <div class=\"ols-figure-caption\">\n          <h3>Electron-rich \u03c0 bond<\/h3>\n          <p>The \u03c0 bond forms exposed electron density above and below the molecular plane, making the alkene attractive to electrophiles.<\/p>\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\/t5-img-16-pireactive.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\/t5-img-16-pireactive.jpg\" alt=\"Two carbon nuclei with a \u03c3 bond between them and an exposed \u03c0 cloud above and below attracting an electrophile, plus a \u03c3 versus \u03c0 table\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t5-img-16-pireactive.jpg\">\n<\/a>\n<\/div>\n<div class=\"ols-figure-caption\"><p>The \u03c0 bond holds exposed electron density above and below the plane, so electrophiles are attracted to this region of high electron density.<\/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: A New Electrophile<\/h2>\n<p>Explain why a different reagent, iodine monochloride, attacks the \u03c0 bond of but-1-ene.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-1061\" class=\"h5p-iframe\" data-content-id=\"1061\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Electrophilic Addition Drag: Iodine Monochloride Meets But-1-ene\"><\/iframe><\/div><\/div>\n<\/section>\n\n    <article class=\"ols-note-card purple\">\n      <div class=\"ols-note-title\"><div class=\"ols-note-icon\">3<\/div><h2>Electrophiles<\/h2><\/div>\n      <p>An <strong>electrophile<\/strong> is an <strong>electron pair acceptor<\/strong>.<\/p>\n      <p>Electrophiles are attracted to regions of high electron density. In alkenes, this means the electrophile is drawn towards the electron-rich \u03c0 bond.<\/p>\n      <p>This attraction begins the electrophilic addition mechanism.<\/p>\n      <div class=\"ols-definition-box\">\n        <div class=\"ols-definition-circle\">E\u207a<\/div>\n        <p><strong>Electrophile:<\/strong> A species that accepts an electron pair from an electron-rich region during a chemical reaction.<\/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\/t5-img-04-electrophiles.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\/t5-img-04-electrophiles.jpg\" alt=\"Definition of an electrophile, three examples (H\u207a, H\u03b4+ in HBr, induced Br\u03b4+ in Br\u2082), and contrast with a nucleophile\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t5-img-04-electrophiles.jpg\">\n<\/a>\n<\/div>\n<div class=\"ols-figure-caption\"><p>An electrophile accepts an electron pair: H\u207a, the H\u03b4+ of HBr or the induced Br\u03b4+ of Br\u2082.<\/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: Find the Electrophile<\/h2>\n<p>Identify the electrophile in a reagent that this page has not used.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-23\" class=\"h5p-iframe\" data-content-id=\"23\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Electrophilic Addition MCQ: The Electrophile in Hydrogen Chloride\"><\/iframe><\/div><\/div>\n<\/section>\n\n    <article class=\"ols-note-card\">\n      <div class=\"ols-note-title\"><div class=\"ols-note-icon\">4<\/div><h2>The Electrophilic Addition Mechanism<\/h2><\/div>\n      <p>In electrophilic addition, the \u03c0 bond breaks and new single bonds are formed. The electrophile accepts an electron pair from the alkene.<\/p>\n      <p>At this stage, students must be careful with curly arrows. A curly arrow shows the movement of an <strong>electron pair<\/strong>, so the arrow should start from a bond or lone pair, not from a positive charge.<\/p>\n      <div class=\"ols-mechanism-grid\">\n        <div class=\"ols-mech-step\"><h3>1. Attraction<\/h3><p>The electrophile is attracted to the high electron density in the \u03c0 bond.<\/p><\/div>\n        <div class=\"ols-mech-step\"><h3>2. Bond breaking<\/h3><p>The \u03c0 bond breaks because it is weaker than the \u03c3 bond.<\/p><\/div>\n        <div class=\"ols-mech-step\"><h3>3. New bonds form<\/h3><p>New single bonds form to give an addition product.<\/p><\/div>\n      <\/div>\n      <div class=\"ols-key-box\"><p><strong>Remember:<\/strong> Electrophilic addition happens because the \u03c0 bond is electron-rich, exposed and relatively easy to break.<\/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: Order the Mechanism<\/h2>\n<p>Put the events of an electrophilic addition you have not seen into the correct order.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-21\" class=\"h5p-iframe\" data-content-id=\"21\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Electrophilic Addition Sort: Hydrogen Chloride with But-2-ene\"><\/iframe><\/div><\/div>\n<\/section>\n\n\n    <article class=\"ols-note-card soft\">\n      <div class=\"ols-note-title\"><div class=\"ols-note-icon\">5<\/div><h2>Exam Link: Why Alkenes React This Way<\/h2><\/div>\n      <p>Exam answers should connect three ideas: the alkene contains a C=C bond, the \u03c0 bond has high electron density, and electrophiles are attracted to this electron-rich region.<\/p>\n      <p>It is not enough to write that alkenes are reactive because they have a double bond. The explanation needs to identify the role of the \u03c0 bond and the electrophile.<\/p>\n      <div class=\"ols-table-wrap\">\n        <table class=\"ols-table\">\n          <thead>\n            <tr><th>Exam phrase<\/th><th>Why it matters<\/th><th>Common mistake to avoid<\/th><\/tr>\n          <\/thead>\n          <tbody>\n            <tr><td><strong>\u03c0 bond has high electron density<\/strong><\/td><td>Explains why an electrophile is attracted to the alkene.<\/td><td>Only saying that the double bond is reactive.<\/td><\/tr>\n            <tr><td><strong>Electrophile accepts an electron pair<\/strong><\/td><td>Links the definition of electrophile to the mechanism.<\/td><td>Calling the electrophile an electron donor.<\/td><\/tr>\n            <tr><td><strong>\u03c0 bond breaks and new single bonds form<\/strong><\/td><td>Explains why the reaction is an addition reaction.<\/td><td>Describing substitution instead of addition.<\/td><\/tr>\n          <\/tbody>\n        <\/table>\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: Explain Why the Alkene Reacts<\/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-740\" class=\"h5p-iframe\" data-content-id=\"740\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Electrophilic Addition Explain: Hex-3-ene Reacts but Hexane Does Not\"><\/iframe><\/div><\/div>\n<\/section>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Hydrogen Iodide and Cyclohexene<\/h2>\n<p>In each round, pick the one accurate statement about this addition.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-736\" class=\"h5p-iframe\" data-content-id=\"736\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Electrophilic Addition Summary: Hydrogen Iodide with Cyclohexene\"><\/iframe><\/div><\/div>\n<\/section>\n\n    \n\n    <section class=\"ols-infographic-full\" aria-label=\"Electrophilic addition mechanism visual summary\">\n      <a class=\"ols-infographic-full-frame\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/skel-21-electrophilic-addition-a-v2.svg\" target=\"_blank\" rel=\"noopener noreferrer\" aria-label=\"Open electrophilic addition mechanism infographic full size\">\n        <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t5-cd-02-electrophilicaddition-v2.svg\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t5-cd-02-electrophilicaddition-v2.svg\" alt=\"General electrophilic addition: \u03c0 bond attacks E\u207a, carbocation forms, then Nu\u207b adds; inset of \u03c0 electrons attracting the \u03b4+ end\" width=\"1515\" height=\"1061\">\n      <\/a>\n      <a class=\"ols-infographic-full-frame\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/skel-21-electrophilic-addition-b-v2.svg\" target=\"_blank\" rel=\"noopener noreferrer\" aria-label=\"Open electrophilic addition mechanism infographic full size\">\n        <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/skel-21-electrophilic-addition-b-v2.svg\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/skel-21-electrophilic-addition-b-v2.svg\" alt=\"General mechanism of electrophilic addition to ethene, through a carbocation, with a summary\" width=\"1514\" height=\"1275\">\n      <\/a>\n    <\/section>\n\n    <section class=\"ols-faq-card\">\n        <h2>FAQs<\/h2>\n        <p>These questions cover the mechanism points examiners mark hardest.<\/p>\n        <div class=\"ols-faq-list\">\n          <div class=\"ols-faq-item\">\n            <h3>Where does the first curly arrow start?<\/h3>\n            <p>In the middle of the C=C bond, from the \u03c0 electrons, and it points to the electrophile. It never starts from an atom or a positive charge.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Is the \u03c0 bond the electrophile?<\/h3>\n            <p>No. The \u03c0 bond is the electron-rich part and donates the pair. The electrophile is the species that accepts it, such as Br<sup>\u03b4+<\/sup> or H<sup>\u03b4+<\/sup>.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why is a carbocation an intermediate and not a product?<\/h3>\n            <p>It forms in one step and is used up in the next, when a negative ion donates a lone pair to the positive carbon.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why is this called addition and not substitution?<\/h3>\n            <p>Nothing leaves the organic molecule. Two atoms or groups add across the C=C bond and one product forms.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Does the negative ion need a lone pair in the mechanism?<\/h3>\n            <p>Yes. Draw the lone pair on Br<sup>&#8211;<\/sup> and start the curly arrow from it to the positive carbon.<\/p>\n          <\/div>\n        <\/div>\n      <\/section>\n\n      <!-- author card (moved to the end, 10 Oct 2026) -->\n      <div class=\"ols-author\">\n        <img decoding=\"async\" class=\"ols-author-avatar-img\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\" alt=\"Dr. Mohammed Al-Fatah\">\n        <div class=\"ols-author-content\">\n          <h2 class=\"ols-author-title\">Written by: Dr. Mohammed Al-Fatah<\/h2>\n          <p class=\"ols-author-description\">Chemistry specialist revision notes for A Level Chemistry.<\/p>\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\"><\/path>\n            <\/svg>\n            View LinkedIn Profile\n          <\/a>\n        <\/div>\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 electrophilic addition to alkene bonding, geometric isomerism and reactions of alkenes.<\/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\/geometric-isomerism\/\">Geometric Isomerism<\/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 ensureLightbox(){\n    var existing = document.querySelector(\".ols-image-lightbox\");\n    if (existing) {\n      return existing;\n    }\n\n    var 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    var 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    var image = document.createElement(\"img\");\n    image.alt = \"\";\n\n    lightbox.appendChild(closeButton);\n    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