{"id":4845,"date":"2026-06-03T06:24:42","date_gmt":"2026-06-03T05:24:42","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/hydrogen\/"},"modified":"2026-10-25T12:12:32","modified_gmt":"2026-10-25T12:12:32","slug":"hydrogen","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/hydrogen\/","title":{"rendered":"Hydrogen"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-alkene-hydrogen-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      --green: #3f8f46;\n      --red: #d94b2b;\n      --gold: #c9973a;\n      --grey-text: #667085;\n      --body-text: #1f2937;\n      --border: rgba(28, 36, 75, 0.14);\n      --shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      --inner-shadow: 0 10px 26px rgba(28, 36, 75, 0.08);\n      font-family: Poppins, Arial, sans-serif;\n      color: var(--navy);\n      background: #ffffff;\n    }\n\n    .ols-revision-page * { box-sizing: border-box; }\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n    .ols-reaction-sublist {\n      list-style: none;\n      margin: 10px 0 0;\n      padding: 0 0 0 14px;\n      display: grid;\n      gap: 7px;\n      border-left: 2px solid rgba(37, 99, 235, 0.18);\n    }\n\n    .ols-reaction-sublist li {\n      font-size: 14px;\n      border-radius: 12px;\n    }\n\n    .ols-reaction-sublist li.active {\n      padding: 0;\n      background: #ffffff;\n      color: var(--blue);\n      font-weight: 700;\n      box-shadow: inset 3px 0 0 var(--blue);\n    }\n\n    .ols-reaction-sublist li.active a {\n      color: var(--blue);\n      font-weight: 700;\n      background: #ffffff;\n      padding-left: 13px;\n    }\n\n    .ols-reaction-sublist li:not(.active) {\n      padding: 0;\n    }\n\n    .ols-reaction-sublist a {\n      padding: 9px 10px;\n      border-radius: 12px;\n      font-size: 14px;\n    }\n\n    .ols-main {\n      min-width: 0;\n      max-width: 970px;\n    }\n\n    .ols-breadcrumbs {\n      display: flex;\n      flex-wrap: wrap;\n      gap: 8px;\n      margin: 10px 0 22px;\n      font-size: 15px;\n      color: var(--grey-text);\n    }\n\n    .ols-breadcrumbs a,\n    .ols-breadcrumbs span {\n      color: var(--grey-text);\n      text-decoration: none;\n      font-weight: 600;\n    }\n\n    .ols-breadcrumbs a:hover {\n      color: var(--blue);\n      text-decoration: underline;\n      text-underline-offset: 3px;\n    }\n\n    .ols-title-card,\n    .ols-note-card,\n    .ols-h5p-card,\n    .ols-related-card {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 28px;\n      box-shadow: var(--shadow);\n      padding: 34px;\n      margin-bottom: 24px;\n      overflow: hidden;\n    }\n\n    .ols-title-card {\n      background: linear-gradient(135deg, #ffffff 0%, #f8fbff 100%);\n    }\n\n    .ols-title-card h1 {\n      margin: 0 0 18px;\n      font-size: clamp(36px, 5vw, 58px);\n      line-height: 1.08;\n      font-weight: 800;\n      letter-spacing: -0.04em;\n      color: #111827;\n    }\n\n    .ols-page-intro {\n      font-size: 19px;\n      line-height: 1.7;\n      font-weight: 300;\n      color: var(--body-text);\n      margin: 0 0 22px;\n    }\n\n    .ols-badges {\n      display: flex;\n      flex-wrap: wrap;\n      gap: 12px;\n      margin-bottom: 22px;\n    }\n\n    .ols-badge {\n      display: inline-flex;\n      align-items: center;\n      padding: 9px 14px;\n      border-radius: 999px;\n      background: #ffffff;\n      border: 1px solid var(--border);\n      font-size: 15px;\n      font-weight: 600;\n      color: var(--navy);\n    }\n\n    .ols-author {\n      display: flex;\n      align-items: center;\n      gap: 14px;\n      padding-top: 22px;\n      border-top: 1px solid var(--border);\n    }\n\n\n\n\n    .ols-note-card.soft {\n      background: linear-gradient(135deg, #ffffff 0%, var(--soft-red) 100%);\n    }\n\n    .ols-note-card.purple {\n      background: linear-gradient(135deg, #ffffff 0%, var(--soft-purple) 100%);\n    }\n\n    .ols-note-title {\n      display: flex;\n      align-items: center;\n      gap: 14px;\n      margin-bottom: 20px;\n    }\n\n    .ols-note-icon {\n      width: 52px;\n      height: 52px;\n      border-radius: 16px;\n      background: var(--navy);\n      color: #ffffff;\n      display: grid;\n      place-items: center;\n      font-size: 24px;\n      font-weight: 800;\n      flex-shrink: 0;\n    }\n\n    .ols-note-title h2,\n    .ols-h5p-card h2,\n    .ols-related-card h2 {\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\n    .ols-h5p-card h2,\n    .ols-related-card h2 {\n      margin-bottom: 14px;\n    }\n\n    .ols-note-card p,\n    .ols-note-card li {\n      font-size: clamp(15px, 1.25vw, 17px);\n      line-height: 1.65;\n      font-weight: 300;\n      color: var(--body-text);\n    }\n\n    .ols-h5p-card p,\n    .ols-related-card p {\n      font-size: clamp(15px, 1.3vw, 18px);\n      line-height: 1.65;\n      font-weight: 300;\n      color: var(--body-text);\n    }\n\n    .ols-note-card strong,\n    .ols-h5p-card strong,\n    .ols-related-card strong {\n      font-weight: 700;\n      color: var(--navy);\n    }\n\n    .ols-note-card ul,\n    .ols-note-card ol {\n      margin: 0;\n      padding-left: 22px;\n    }\n\n    .ols-key-box {\n      margin-top: 20px;\n      background: var(--soft-green);\n      border: 1px solid rgba(63, 143, 70, 0.25);\n      border-radius: 20px;\n      padding: 18px 20px;\n    }\n\n    .ols-key-box p {\n      margin: 0;\n      font-weight: 400;\n      color: var(--navy);\n    }\n\n    .ols-reaction-summary {\n      display: grid;\n      grid-template-columns: repeat(2, minmax(0, 1fr));\n      gap: 14px;\n      margin-top: 20px;\n    }\n\n    .ols-summary-item {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 16px;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-summary-item span {\n      display: block;\n      font-size: 13px;\n      font-weight: 700;\n      color: var(--grey-text);\n      margin-bottom: 6px;\n    }\n\n    .ols-summary-item strong {\n      display: block;\n      font-size: 16px;\n      line-height: 1.45;\n      color: var(--navy);\n    }\n\n    .ols-figure-card {\n      margin: 26px 0 4px;\n      border: 1px solid var(--border);\n      border-radius: 26px;\n      overflow: hidden;\n      background: #ffffff;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-figure-image {\n      width: 100%;\n      min-height: 260px;\n      display: flex;\n      align-items: center;\n      justify-content: center;\n      background: #ffffff;\n      padding: 20px;\n    }\n\n    .ols-figure-image img {\n      max-width: 100%;\n      height: auto;\n      display: block;\n    }\n\n    .ols-figure-caption {\n      padding: 22px 26px 24px;\n      background: linear-gradient(135deg, #ffffff, #f8fbff);\n    }\n\n    .ols-figure-caption p {\n      margin: 0;\n      color: #5f6b85;\n      font-size: clamp(16px, 1.4vw, 19px);\n      line-height: 1.65;\n      font-weight: 300;\n      font-style: italic;\n    }\n\n    .ols-mechanism-steps {\n      display: grid;\n      gap: 14px;\n      margin-top: 20px;\n    }\n\n    .ols-step-card {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 20px;\n      padding: 18px 20px;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-step-card h3 {\n      margin: 0 0 8px;\n      font-size: 21px;\n      line-height: 1.25;\n      color: var(--navy);\n    }\n\n    .ols-step-card p {\n      margin: 0;\n    }\n\n    .ols-definition-box {\n      background: linear-gradient(135deg, #ffffff, var(--soft-purple));\n      border: 2px dashed rgba(122, 62, 157, 0.35);\n      border-radius: 24px;\n      padding: 26px;\n      margin-top: 22px;\n      display: grid;\n      grid-template-columns: 1fr;\n      gap: 16px;\n      align-items: center;\n    }\n\n    .ols-definition-circle {\n      width: 105px;\n      height: 105px;\n      border-radius: 50%;\n      background: linear-gradient(135deg, #9b59b6, #6f3d96);\n      color: white;\n      display: grid;\n      place-items: center;\n      font-size: 26px;\n      font-weight: 800;\n      text-align: center;\n      margin: 0 auto;\n    }\n\n    .ols-h5p-card {\n      background: linear-gradient(135deg, #ffffff 0%, #f7f0ff 100%);\n    }\n\n    .ols-h5p-frame {\n      margin-top: 22px;\n      padding: 18px;\n      border-radius: 24px;\n      background: #ffffff;\n      border: 1px solid var(--border);\n      box-shadow: inset 0 0 0 1px rgba(28, 36, 75, 0.03);\n    }\n\n    .ols-related-grid {\n      display: grid;\n      grid-template-columns: repeat(3, minmax(0, 1fr));\n      gap: 16px;\n      margin-top: 18px;\n    }\n\n    .ols-related-item {\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 18px;\n      background: #ffffff;\n      color: var(--navy);\n      text-decoration: none;\n      font-weight: 600;\n      line-height: 1.5;\n      transition: transform 0.2s ease, box-shadow 0.2s ease;\n    }\n\n    .ols-related-item:hover {\n      transform: translateY(-2px);\n      box-shadow: 0 10px 22px rgba(28, 36, 75, 0.08);\n    }\n\n    .ols-unlock {\n      background: linear-gradient(135deg, var(--navy), #0f4fa8);\n      border-radius: 30px;\n      padding: 36px;\n      color: #ffffff;\n      box-shadow: var(--shadow);\n      text-align: center;\n      margin: 30px 0 24px;\n    }\n\n    .ols-unlock h2 {\n      margin: 0 0 12px;\n      font-size: clamp(30px, 4vw, 46px);\n      line-height: 1.15;\n      font-weight: 800;\n      color: #ffffff;\n      text-align: center;\n    }\n\n    .ols-unlock p {\n      margin: 0 auto 24px;\n      max-width: 700px;\n      font-size: 20px;\n      line-height: 1.6;\n      font-weight: 300;\n      text-align: center;\n      color: #ffffff;\n    }\n\n    .ols-cta-button {\n      display: inline-flex;\n      align-items: center;\n      justify-content: center;\n      padding: 14px 26px;\n      border-radius: 999px;\n      background: #ffffff;\n      color: var(--navy);\n      text-decoration: none;\n      font-weight: 700;\n      transition: background 0.2s ease, color 0.2s ease, transform 0.2s ease;\n    }\n\n    .ols-cta-button:hover {\n      background: #f8fbff;\n      color: var(--blue);\n      transform: translateY(-1px);\n    }\n\n    @media (max-width: 1050px) {\n\n\n\n      .ols-reaction-sublist {\n        grid-template-columns: 1fr;\n      }\n\n      .ols-main {\n        max-width: none;\n      }\n\n      .ols-related-grid {\n        grid-template-columns: repeat(2, minmax(0, 1fr));\n      }\n    }\n\n    @media (max-width: 760px) {\n\n      .ols-title-card,\n      .ols-note-card,\n      .ols-h5p-card,\n      .ols-related-card,\n      .ols-unlock {\n        padding: 24px 18px;\n        border-radius: 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: 210px;\n        padding: 14px;\n      }\n\n      .ols-figure-caption {\n        padding: 18px;\n      }\n\n      .ols-topic-list,\n      .ols-related-grid,\n      .ols-reaction-summary {\n        grid-template-columns: 1fr;\n      }\n    }\n    .ols-author {\n      display: flex;\n      align-items: center;\n      gap: 20px;\n      padding: 28px;\n      border-radius: 28px;\n      background: linear-gradient(135deg, #ffffff 0%, #f8fbff 100%);\n      border: 1px solid rgba(28, 36, 75, 0.12);\n      box-shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      margin-top: 22px;\n    }\n    .ols-author-avatar-img {\n      width: 92px;\n      height: 92px;\n      border-radius: 50%;\n      object-fit: cover;\n      object-position: center;\n      flex-shrink: 0;\n      border: 4px solid #ffffff;\n      box-shadow: 0 14px 32px rgba(28, 36, 75, 0.18), 0 0 0 1px rgba(28, 36, 75, 0.10);\n      transition: transform 0.25s ease, box-shadow 0.25s ease;\n    }\n    .ols-author:hover .ols-author-avatar-img {\n      transform: scale(1.04);\n      box-shadow: 0 20px 42px rgba(28, 36, 75, 0.22), 0 0 0 1px rgba(28, 36, 75, 0.10);\n    }\n    .ols-author-content { min-width: 0; }\n    .ols-author-title {\n      margin: 0 0 4px;\n      font-size: clamp(24px, 3vw, 34px);\n      line-height: 1.15;\n      font-weight: 700;\n      color: var(--navy);\n      letter-spacing: -0.03em;\n    }\n    .ols-author-description {\n      margin: 0;\n      font-size: 17px;\n      line-height: 1.7;\n      font-weight: 300;\n      color: var(--grey-text);\n    }\n    .ols-linkedin-pill {\n      display: inline-flex;\n      align-items: center;\n      justify-content: center;\n      gap: 10px;\n      margin-top: 16px;\n      padding: 11px 18px;\n      border-radius: 999px;\n      background: linear-gradient(135deg, #0A66C2, #004182);\n      color: #ffffff;\n      text-decoration: none;\n      font-size: 14px;\n      line-height: 1;\n      font-weight: 700;\n      letter-spacing: 0.01em;\n      box-shadow: 0 10px 22px rgba(10, 102, 194, 0.24);\n      position: relative;\n      overflow: hidden;\n      transition: transform 0.22s ease, box-shadow 0.22s ease;\n    }\n    .ols-linkedin-pill:hover {\n      transform: translateY(-3px) scale(1.03);\n      box-shadow: 0 16px 34px rgba(10, 102, 194, 0.34), 0 0 0 6px rgba(10, 102, 194, 0.10);\n    }\n    .ols-linkedin-icon { width: 18px; height: 18px; display: block; flex-shrink: 0; }\n    .ols-attribution-card {\n      background: linear-gradient(135deg, #ffffff, #f8fbff);\n      border: 1px solid rgba(28, 36, 75, 0.14);\n      border-radius: 28px;\n      box-shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      padding: 34px;\n      margin-bottom: 24px;\n      overflow: hidden;\n      box-sizing: border-box;\n    }\n    .ols-attribution-card p {\n      margin: 0;\n      font-size: 14px;\n      line-height: 1.65;\n      font-weight: 300;\n      color: #667085;\n    }\n    .ols-attribution-card strong { font-weight: 700; color: #1C244B; }\n  \n\n    \/* OLS non-clipping hover zoom and fullscreen image system *\/\n    .ols-alkene-hydrogen-page,\n    .ols-alkene-hydrogen-page .ols-main,\n    .ols-alkene-hydrogen-page .ols-title-card,\n    .ols-alkene-hydrogen-page .ols-note-card,\n    .ols-alkene-hydrogen-page .ols-figure-card,\n    .ols-alkene-hydrogen-page .ols-figure-image,\n    .ols-alkene-hydrogen-page .ols-image-fullscreen-button {\n      overflow: visible !important;\n    }\n\n    .ols-alkene-hydrogen-page .ols-figure-card {\n      position: relative;\n      z-index: 1;\n    }\n\n    .ols-alkene-hydrogen-page .ols-figure-image {\n      position: relative;\n      border-radius: 26px 26px 0 0;\n    }\n\n    .ols-alkene-hydrogen-page .ols-image-fullscreen-button {\n      display: inline-block;\n      max-width: 100%;\n      line-height: 0;\n      position: relative;\n      z-index: 2;\n      cursor: zoom-in;\n      padding: 0;\n      margin: 0;\n      border: 0;\n      background: transparent;\n      font: inherit;\n      appearance: none;\n      -webkit-appearance: none;\n    }\n\n    .ols-alkene-hydrogen-page .ols-hover-zoom-img {\n      max-width: 100%;\n      height: auto;\n      display: block;\n      position: relative;\n      z-index: 2;\n      transform-origin: center center;\n      transition: transform 0.28s ease, box-shadow 0.28s ease, border-radius 0.28s ease;\n      cursor: zoom-in;\n    }\n\n    .ols-alkene-hydrogen-page .ols-image-fullscreen-button:hover,\n    .ols-alkene-hydrogen-page .ols-image-fullscreen-button:focus-visible {\n      z-index: 80;\n    }\n\n    .ols-alkene-hydrogen-page .ols-image-fullscreen-button:hover .ols-hover-zoom-img,\n    .ols-alkene-hydrogen-page .ols-image-fullscreen-button:focus-visible .ols-hover-zoom-img {\n      transform: scale(1.5);\n      box-shadow: 0 28px 70px rgba(28, 36, 75, 0.24);\n      border-radius: 18px;\n      z-index: 90;\n    }\n\n    .ols-alkene-hydrogen-page .ols-lightbox-overlay {\n      position: fixed;\n      inset: 0;\n      z-index: 999999;\n      display: none;\n      align-items: center;\n      justify-content: center;\n      padding: 28px;\n      background: rgba(8, 13, 30, 0.88);\n    }\n\n    .ols-alkene-hydrogen-page .ols-lightbox-overlay.is-open {\n      display: flex;\n    }\n\n    .ols-alkene-hydrogen-page .ols-lightbox-img {\n      max-width: min(96vw, 1400px);\n      max-height: 92vh;\n      width: auto;\n      height: auto;\n      object-fit: contain;\n      border-radius: 18px;\n      background: #ffffff;\n      box-shadow: 0 30px 90px rgba(0, 0, 0, 0.42);\n    }\n\n    .ols-alkene-hydrogen-page .ols-lightbox-close {\n      position: fixed;\n      top: 18px;\n      right: 22px;\n      width: 46px;\n      height: 46px;\n      border: 0;\n      border-radius: 999px;\n      background: #ffffff;\n      color: #1C244B;\n      font-size: 30px;\n      line-height: 1;\n      font-weight: 700;\n      cursor: pointer;\n      box-shadow: 0 12px 30px rgba(0, 0, 0, 0.25);\n    }\n\n    @media (max-width: 760px) {\n      .ols-alkene-hydrogen-page .ols-image-fullscreen-button:hover .ols-hover-zoom-img,\n      .ols-alkene-hydrogen-page .ols-image-fullscreen-button:focus-visible .ols-hover-zoom-img {\n        transform: none;\n        box-shadow: none;\n        border-radius: 0;\n      }\n    }\n\n.ols-faq-card,\n    .ols-quicksnap-card {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 28px;\n      box-shadow: var(--shadow);\n      padding: 34px;\n      margin-bottom: 24px;\n      overflow: hidden;\n    }\n.ols-faq-card h2,\n    .ols-quicksnap-card h2,\n    .ols-infographic-title {\n      margin: 0;\n      font-size: clamp(28px, 3.5vw, 42px);\n      line-height: 1.15;\n      font-weight: 800;\n      color: #111827;\n      letter-spacing: -0.03em;\n    }\n.ols-faq-card h2,\n    .ols-quicksnap-card h2 {\n      margin-bottom: 14px;\n    }\n.ols-faq-card p,\n    .ols-quicksnap-card p {\n      font-size: clamp(15px, 1.25vw, 17px);\n      line-height: 1.65;\n      font-weight: 300;\n      color: var(--body-text);\n    }\n.ols-faq-card strong,\n    .ols-quicksnap-card strong {\n      font-weight: 700;\n      color: var(--navy);\n    }\n.ols-faq-list {\n      display: grid;\n      gap: 14px;\n      margin-top: 18px;\n    }\n.ols-faq-item {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 18px 20px;\n      box-shadow: var(--inner-shadow);\n    }\n.ols-faq-item h3 {\n      margin: 0 0 8px;\n      font-size: 20px;\n      line-height: 1.3;\n      color: var(--navy);\n    }\n.ols-faq-item p {\n      margin: 0;\n      font-size: 16px;\n      line-height: 1.65;\n      color: var(--body-text);\n    }\n.ols-faq-card,\n      .ols-quicksnap-card,\n      .ols-attribution-card {\n        padding: 24px 18px;\n        border-radius: 22px;\n      }\n<\/style>\n\n  <aside class=\"ols-sidebar\">\r\n  <div class=\"ols-sidebar-header\">\r\n    <h3>Revision Notes<\/h3>\r\n    <p>A Level Chemistry<\/p>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Topic 6 Organic Chemistry I<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/\">Introduction to Organic Chemistry<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/iupac-rules\/\">IUPAC Rules<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/alkene\/\">Alkene<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/alcohol\/\">Alcohol<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/halogenoalkanes\/\">Halogenoalkanes<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/aldehyde\/\">Aldehyde<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/ketone\/\">Ketone<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/carboxylic-acid\/\">Carboxylic Acid<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/ester\/\">Ester<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/isomerism\/\">Isomerism<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/\">Alkanes<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/\">Alkanes from Crude Oil<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/fractional-distillation\/\">Fractional Distillation<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/cracking\/\">Cracking<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/reforming\/\">Reforming<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/\">Alkanes as Fuel<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/combustion\/\">Combustion<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/oxides-of-sulfur\/\">Oxides of Sulfur<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/oxides-of-nitrogen\/\">Oxides of Nitrogen<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/catalytic-converter\/\">Catalytic Converter<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/alternative-fuel\/\">Alternative Fuel<\/a>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/\">Reactions of Alkanes<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/free-radical-substitution\/\">Free Radical Substitution<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/initiation\/\">Initiation<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/propagation\/\">Propagation<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/termination\/\">Termination<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/further-substitution\/\">Further Substitution<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/\">Alkenes<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/alkene-bonding\/\">Alkene Bonding<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/geometric-isomerism\/\">Geometric Isomerism<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/electrophilic-addition-mechanism\/\">Electrophilic Addition Mechanism<\/a>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/\">Reactions of Alkenes<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/halogens\/\">Halogens<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/hydrogen-halide\/\">Hydrogen Halide<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/bromine-water\/\">Bromine Water<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/hydrogen\/\">Hydrogen<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/steam\/\">Steam<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/kmno4\/\">KMnO4<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/polymerisation-reactions\/\">Polymerisation Reactions<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/polymer-waste\/\">Polymer Waste<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/halogenoalkanes\/\">Halogenoalkanes<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alcohols\/\">Alcohols<\/a>\r\n      <\/li>\r\n\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Next Topics<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-7-modern-analytical-techniques-i\/\">Topic 7 Modern Analytical Techniques I<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-5-formulae-equations-and-amounts-of-substance\/\">Topic 5 Formulae, Equations &amp; Amounts<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/\">Topic 4 Inorganic Chemistry &amp; The Periodic Table<\/a>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n<\/aside>\r\n\r\n<script>\r\n(function() {\r\n  function normalisePath(path) {\r\n    return String(path || '')\r\n      .split('?')[0]\r\n      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(parentLink) {\r\n            parentLink.setAttribute('aria-current', 'true');\r\n            parentLink.setAttribute('tabindex', '-1');\r\n            parentLink.setAttribute('data-ols-disabled-parent', '1');\r\n          }\r\n\r\n          var higherSub = parentLi.parentElement.closest('.ols-subtopic-list');\r\n          parentLi = higherSub ? higherSub.closest('li') : null;\r\n        }\r\n      } else {\r\n        if (matchedLi) {\r\n          matchedLi.classList.add('parent-active', 'active-main');\r\n          matched.setAttribute('aria-current', 'page');\r\n          matched.setAttribute('tabindex', '-1');\r\n          matched.setAttribute('data-ols-disabled-parent', '1');\r\n        }\r\n      }\r\n    }\r\n\r\n    return true;\r\n  }\r\n\r\n  if (!highlightActive()) {\r\n    document.addEventListener('DOMContentLoaded', highlightActive);\r\n  }\r\n})();\r\n<\/script>\n\n  <main class=\"ols-main\">\n<nav aria-label=\"Breadcrumb\" class=\"ols-breadcrumbs\"><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\">Revision Notes<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\">A Level Chemistry<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/\">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        <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> \/\n        <span>Hydrogen<\/span><\/nav>\n<header class=\"ols-title-card\">\n<h1>Reactions of Alkenes with Hydrogen<\/h1>\n<p class=\"ols-page-intro\">A concise revision guide to the reaction of alkenes with hydrogen, including the change from alkene to alkane, the use of a nickel catalyst and why this reaction is both an addition reaction and a reduction reaction.<\/p>\n<div class=\"ols-badges\"><div class=\"ols-badge\">Paper 2<\/div><div class=\"ols-badge\">Topic 6: Organic Chemistry I<\/div><div class=\"ols-badge\">9CH0\/02<\/div><\/div>\n<\/header>\n<!-- 3D card: hydrogenation-catalyst (22 Oct 2026) -->\n<!-- Copyright (c) 2026 Dr. Mohammed Al-Fatah, onlinelearningsystem.net. 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border-radius:22px;}\n  .ols-hyc-001 h2.hyc-title{font-size:20.5px;}\n  .ols-hyc-001 p.hyc-sub{font-size:13.5px;}\n  .ols-hyc-001 .hyc-stage{height:400px;}\n  .ols-hyc-001 .hyc-rowlab{min-width:100%;}\n  .ols-hyc-001 .hyc-seg button{padding:9px 13px; font-size:13px;}\n  .ols-hyc-001 .hyc-lab{font-size:10.5px; padding:4px 8px;}\n  .ols-hyc-001 .hyc-lab.l-part{font-size:9.5px; padding:3px 7px;}\n  .ols-hyc-001 .hyc-lab.l-read{font-size:12px; padding:5px 9px;}\n  .ols-hyc-001 .hyc-caption{font-size:10.5px; padding:5px 9px; max-width:64%;}\n  .ols-hyc-001 .hyc-badge{font-size:10.5px; padding:4px 9px;}\n  .ols-hyc-001 .hyc-badge.b-eq{font-size:11px;}\n  .ols-hyc-001 .hyc-badges{max-width:calc(100% - 28px);}\n  .ols-hyc-001 .hyc-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-hyc-001 .hyc-hint{display:none;}\n  .ols-hyc-001 .hyc-caption{max-width:calc(100% - 28px);}\n}\n@media (prefers-reduced-motion:reduce){\n  .ols-hyc-001 .hyc-seg button,.ols-hyc-001 .hyc-pill{transition:none;}\n}\n\n.ols-cc-hyc-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-hyc-001 a{color:#aab0c0; text-decoration:none;}\n.ols-cc-hyc-001 a:hover{text-decoration:underline;}\n.ols-hyc-001 .hyc-seg button{display:inline-flex; align-items:center;}\n.ols-hyc-001 .hyc-seg button .hyc-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-hyc-001 .hyc-seg button[aria-pressed=\"true\"] .hyc-n{background:#ffffff; color:#2563eb;}\n<\/style>\n\n<div class=\"hyc-head\">\n  <h2 class=\"hyc-title\">Hydrogenation on a Catalyst Surface<\/h2>\n  <p class=\"hyc-sub\">Choose a step to watch ethene and hydrogen meet on a nickel surface and leave as ethane.<\/p>\n<\/div>\n\n<div class=\"hyc-stage\" id=\"hycStage\">\n  <canvas class=\"hyc-canvas\" id=\"hycCanvas\"><\/canvas>\n  <div class=\"hyc-overlay\" id=\"hycOverlay\"><\/div>\n  <div class=\"hyc-caption\" id=\"hycCaption\"><\/div>\n  <div class=\"hyc-hint\" id=\"hycHint\">Drag to rotate<\/div>\n  <div class=\"hyc-badges\" id=\"hycBadges\"><\/div>\n<\/div>\n\n<div class=\"hyc-controls\">\n  <div class=\"hyc-row\">\n    <span class=\"hyc-rowlab\">Step<\/span>\n    <div class=\"hyc-seg\" role=\"group\" aria-label=\"Step\">\n      <button type=\"button\" data-step=\"1\" aria-pressed=\"true\"><span class=\"hyc-n\">1<\/span>Adsorb<\/button>\n      <button type=\"button\" data-step=\"2\" aria-pressed=\"false\"><span class=\"hyc-n\">2<\/span>Split<\/button>\n      <button type=\"button\" data-step=\"3\" aria-pressed=\"false\"><span class=\"hyc-n\">3<\/span>Add<\/button>\n      <button type=\"button\" data-step=\"4\" aria-pressed=\"false\"><span class=\"hyc-n\">4<\/span>Desorb<\/button>\n    <\/div>\n  <\/div>\n\n  <div class=\"hyc-row\">\n    <span class=\"hyc-rowlab\">View<\/span>\n    <button type=\"button\" class=\"hyc-pill\" id=\"hycResetV\">Reset view<\/button>\n  <\/div>\n<\/div>\n\n<div class=\"hyc-info\">\n  <h3 id=\"hycInfoTitle\"><\/h3>\n  <p id=\"hycInfoText\"><\/p>\n  <div class=\"hyc-facts\" id=\"hycFacts\"><\/div>\n  <div class=\"hyc-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:#b2b8c4\"><\/i>Nickel<\/span>\n    <span><i class=\"k-ball\" style=\"background:#2f5f9a\"><\/i>Weak bond to the surface<\/span>\n  <\/div>\n<\/div>\n\n<script src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/JS\/hydrogenation-catalyst.js?v=20261025p\"><\/script>\n<\/section>\n\n<p class=\"ols-cc-hyc-001\">&copy; Dr. Mohammed Al-Fatah &#8211; <a href=\"https:\/\/www.onlinelearningsystem.net\" target=\"_blank\" rel=\"noopener\">onlinelearningsystem.net<\/a><\/p>\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: Catalysts and Hardening Oils<\/h2>\n<p>Answer three quick GCSE questions before you start.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"748\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">1<\/div>\n<h2>The Overall Reaction<\/h2>\n<\/div>\n<p>Alkenes react with <strong>hydrogen, H<sub>2<\/sub><\/strong>, in the presence of a <strong>nickel catalyst<\/strong>. The reaction converts an <strong>alkene<\/strong> into an <strong>alkane<\/strong>.<\/p>\n<p>The C=C double bond opens and one hydrogen atom adds to each carbon atom from the original double bond. This removes the alkene functional group and produces a saturated hydrocarbon.<\/p>\n<p>For example, <strong>ethene<\/strong> reacts with hydrogen to form <strong>ethane<\/strong>.<\/p>\n<div class=\"ols-reaction-summary\">\n<div class=\"ols-summary-item\"><span>Functional group change<\/span><strong>Alkene \u2192 alkane<\/strong><\/div>\n<div class=\"ols-summary-item\"><span>Reagent<\/span><strong>Hydrogen, H<sub>2<\/sub><\/strong><\/div>\n<div class=\"ols-summary-item\"><span>Conditions<\/span><strong>Nickel catalyst<\/strong><\/div>\n<div class=\"ols-summary-item\"><span>Type of reaction<\/span><strong>Addition and reduction<\/strong><\/div>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Key idea:<\/strong> Hydrogen adds across the C=C double bond, so the alkene becomes an alkane.<\/p>\n<\/div>\n<div class=\"ols-figure-card\">\n<div class=\"ols-figure-image\">\n<button class=\"ols-image-fullscreen-button ols-lightbox-trigger\" type=\"button\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/skel-30-ethene-hydrogenation.svg\" data-fullscreen-alt=\"Hydrogenation of ethene to ethane with a nickel catalyst, with the added hydrogen atoms highlighted\" aria-label=\"Open image fullscreen\"><img decoding=\"async\" alt=\"Ethene plus hydrogen over nickel giving ethane, with the added hydrogen atoms highlighted\" class=\"ols-hover-zoom-img ols-lightbox-target\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-cd-19-hydrogenation.svg\" width=\"1416\" height=\"756\"\/><\/button>\n<\/div>\n<div class=\"ols-figure-caption\">\n<p>Ethene reacts with H<sub>2<\/sub>; the C=C double bond is converted into a C-C single bond as ethane forms.<\/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\/t4-cd-19b-propenehydrog.svg\" 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-cd-19b-propenehydrog.svg\" alt=\"Ethene plus hydrogen over nickel giving ethane, with the added hydrogen atoms highlighted\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-cd-19b-propenehydrog.svg\">\n<\/a>\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: How Much Hydrogen?<\/h2>\n<p>Apply the conditions to a molecule that has more than one double bond.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-39\" class=\"h5p-iframe\" data-content-id=\"39\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Hydrogenation MCQ: A Diene with an Excess of Hydrogen\"><\/iframe><\/div><\/div>\n<\/section>\n\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">2<\/div>\n<h2>Why This Is an Addition Reaction<\/h2>\n<\/div>\n<p>This reaction is an <strong>addition reaction<\/strong> because atoms are added across the carbon-carbon double bond.<\/p>\n<p>The alkene starts with a C=C double bond, meaning it is <strong>unsaturated<\/strong>. During the reaction, the double bond opens and two new C-H bonds form.<\/p>\n<p>The product is an alkane, which is <strong>saturated<\/strong> because it contains only single covalent bonds between carbon atoms.<\/p>\n<div class=\"ols-definition-box\">\n<div class=\"ols-definition-circle\">H<sub>2<\/sub><\/div>\n<p><strong>Hydrogenation:<\/strong> The addition of hydrogen across a C=C double bond, converting an alkene into an alkane.<\/p>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Remember:<\/strong> In alkene addition reactions, the C=C double bond is the reactive site. The double bond opens so new atoms can bond to the two carbon atoms.<\/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-28-nickelsurface.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-28-nickelsurface.jpg\" alt=\"Four frames on a nickel surface: H\u2082 and an alkene adsorb, the H\u2013H bond weakens, H atoms add across the C=C, the alkane leaves\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t5-img-28-nickelsurface.jpg\">\n<\/a>\n<\/div>\n<div class=\"ols-figure-caption\"><p>Hydrogen and the alkene are held on the nickel surface, the H\u2013H bond breaks and one hydrogen atom adds to 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: Formulae, Names and Amounts<\/h2>\n<p>Answer as quickly as you can, using alkenes that are not on this page.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-40\" class=\"h5p-iframe\" data-content-id=\"40\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Hydrogenation Quick-Fire: Formulae, Names and Amounts\"><\/iframe><\/div><\/div>\n<\/section>\n\n<article class=\"ols-note-card purple\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">3<\/div>\n<h2>Why This Is Also a Reduction Reaction<\/h2>\n<\/div>\n<p>The reaction with hydrogen can also be described as a <strong>reduction reaction<\/strong>.<\/p>\n<p>In organic chemistry, reduction often means the addition of hydrogen to a molecule. Since the alkene gains hydrogen atoms, the reaction is described as reduction.<\/p>\n<p>This is why the same reaction can be correctly described in two ways: <strong>addition<\/strong>, because atoms add across the double bond, and <strong>reduction<\/strong>, because hydrogen is added.<\/p>\n<div class=\"ols-mechanism-steps\">\n<div class=\"ols-step-card\">\n<h3>Step 1: Hydrogen is the reagent<\/h3>\n<p>The alkene reacts with H<sub>2<\/sub> in the presence of a nickel catalyst.<\/p>\n<\/div>\n<div class=\"ols-step-card\">\n<h3>Step 2: The double bond opens<\/h3>\n<p>The C=C bond is replaced by a C-C single bond as new C-H bonds form.<\/p>\n<\/div>\n<div class=\"ols-step-card\">\n<h3>Step 3: An alkane forms<\/h3>\n<p>The product is saturated because it no longer contains the alkene C=C functional group.<\/p>\n<\/div>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Exam focus:<\/strong> If asked for the reaction type, addition is essential. Reduction is also valid because hydrogen is added.<\/p>\n<\/div>\n<div class=\"ols-figure-card ols-zoom-pop\">\n<div class=\"ols-figure-image\">\n<a class=\"ols-image-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-img-73-hardening.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-73-hardening.jpg\" alt=\"Liquid vegetable oil hydrogenated over nickel to solid margarine, with kinked and straight chain packing\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-img-73-hardening.jpg\">\n<\/a>\n<\/div>\n<div class=\"ols-figure-caption\"><p>Adding hydrogen to C=C bonds in oils straightens the chains, so they pack closer and the fat is solid.<\/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: Two Names for One Reaction<\/h2>\n<p>Drag the words into place to describe the hydrogenation of a ring alkene that is not on this page.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-1273\" class=\"h5p-iframe\" data-content-id=\"1273\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Hydrogenation Drag: Cyclohexene, Addition and Reduction\"><\/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: Pick the Accurate Statement<\/h2>\n<p>In each round, choose the one statement that is accurate.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-41\" class=\"h5p-iframe\" data-content-id=\"41\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Hydrogenation Summary: Skeletons, Names and the Nickel\"><\/iframe><\/div><\/div>\n<\/section>\n\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">4<\/div>\n<h2>Common Exam Mistakes<\/h2>\n<\/div>\n<p>Students often lose marks by forgetting the <strong>nickel catalyst<\/strong>, or by describing the reaction as substitution. This is not substitution because no atom is replaced.<\/p>\n<p>Another common error is to leave the product as an alkene. The product must be an <strong>alkane<\/strong>, because the carbon-carbon double bond has been removed.<\/p>\n<p>For a simple reaction question, the safest answer should include the reagent, condition, product type and reaction type.<\/p>\n<div class=\"ols-reaction-summary\">\n<div class=\"ols-summary-item\"><span>Do say<\/span><strong>Hydrogen adds across the C=C double bond.<\/strong><\/div>\n<div class=\"ols-summary-item\"><span>Condition<\/span><strong>Use a nickel catalyst.<\/strong><\/div>\n<div class=\"ols-summary-item\"><span>Product type<\/span><strong>Alkane, not alkene.<\/strong><\/div>\n<div class=\"ols-summary-item\"><span>Do not say<\/span><strong>Substitution reaction.<\/strong><\/div>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Exam focus:<\/strong> Link the functional group change to the reaction type: alkene to alkane happens because hydrogen adds across the C=C double bond.<\/p>\n<\/div>\n<\/article>\n\n<section class=\"ols-faq-card\">\n        <h2>FAQs<\/h2>\n        <p>These questions cover the hydrogenation points that cost marks.<\/p>\n        <div class=\"ols-faq-list\">\n          <div class=\"ols-faq-item\">\n            <h3>What does the nickel catalyst do?<\/h3>\n            <p>It adsorbs hydrogen and the alkene on its surface and weakens the H-H bond, so the reaction is fast at a moderate temperature.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Is hydrogenation addition or reduction?<\/h3>\n            <p>Both. Hydrogen adds across the C=C bond, which is addition, and gaining hydrogen counts as reduction in organic chemistry.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>What forms when propene reacts with hydrogen?<\/h3>\n            <p>Propane, CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>3<\/sub>. One hydrogen atom adds to each carbon of the double bond.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>How many moles of H<sub>2<\/sub> does a diene take?<\/h3>\n            <p>Two. Each C=C bond takes one mole of H<sub>2<\/sub>, so counting moles of H<sub>2<\/sub> absorbed tells you how many double bonds are present.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Where is hydrogenation used?<\/h3>\n            <p>In making margarine. Some C=C bonds in vegetable oils are hydrogenated, which raises the melting temperature so the fat is solid at room temperature.<\/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\" alt=\"Dr. Mohammed Al-Fatah\" class=\"ols-author-avatar-img\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\"\/>\n<div class=\"ols-author-content\">\n<h2 class=\"ols-author-title\">\n        Written by: Dr. Mohammed Al-Fatah\n      <\/h2>\n<p class=\"ols-author-description\">\n        Chemistry specialist revision notes for A Level Chemistry.\n      <\/p>\n<a class=\"ols-linkedin-pill\" href=\"https:\/\/www.linkedin.com\/in\/doctormohammedfatah\/\" rel=\"noopener noreferrer\" target=\"_blank\">\n<svg aria-hidden=\"true\" class=\"ols-linkedin-icon\" fill=\"currentColor\" viewbox=\"0 0 24 24\">\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 5 by linking hydrogenation to halogen addition, hydrogen halide addition and hydration with steam.<\/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\/reactions-of-alkenes\/bromine-water\/\">Bromine Water<\/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\/steam\/\">Steam<\/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\/hydrogen-halide\/\">Hydrogen Halide<\/a>\n<\/div>\n<\/section>\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\n<script type=\"application\/ld+json\">\n{\n    \"@context\": \"https:\/\/schema.org\",\n    \"@graph\": [\n        {\n            \"@type\": \"Organization\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/#organization\",\n            \"name\": \"Online Learning System\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/\",\n            \"logo\": {\n                \"@type\": \"ImageObject\",\n                \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2025\/07\/a-level-chemistry-virtual-lesson-tutor.webp\"\n            }\n        },\n        {\n            \"@type\": \"WebSite\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/#website\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/\",\n            \"name\": \"Online Learning System\",\n            \"publisher\": {\n   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