{"id":256371,"date":"2025-07-16T09:10:29","date_gmt":"2025-07-16T09:10:29","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=256371"},"modified":"2025-07-16T09:10:31","modified_gmt":"2025-07-16T09:10:31","slug":"which-of-the-following-is-the-most-reactive-substrate-in-an-e1-reaction","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/07\/16\/which-of-the-following-is-the-most-reactive-substrate-in-an-e1-reaction\/","title":{"rendered":"Which of the following is the most reactive substrate in an E1 reaction"},"content":{"rendered":"\n

Which of the following is the most reactive substrate in an E1 reaction? Br Br I II III IV \u039f\u0399 \u039f\u0399\u0399 O III O IV<\/p>\n\n\n\n

The Correct Answer and Explanation is:<\/mark><\/strong><\/p>\n\n\n\n

Correct Answer: III<\/strong><\/p>\n\n\n\n

Explanation<\/h3>\n\n\n\n

To determine which substrate is the most reactive in an E1 reaction<\/strong>, we need to understand the E1 mechanism<\/strong>.<\/p>\n\n\n\n

E1 (Elimination Unimolecular)<\/strong> reactions follow two main steps:<\/p>\n\n\n\n

    \n
  1. Formation of a carbocation<\/strong> after the leaving group (like Br or I) leaves.<\/li>\n\n\n\n
  2. Loss of a proton (H\u207a)<\/strong> from a \u03b2-carbon to form a double bond.<\/li>\n<\/ol>\n\n\n\n

    The rate-determining step<\/strong> is the formation of the carbocation<\/strong>, so the stability of the carbocation<\/strong> is crucial. The more stable the carbocation intermediate, the faster and more favorable the E1 reaction.<\/p>\n\n\n\n

    Key factors influencing E1 reactivity:<\/strong><\/p>\n\n\n\n

      \n
    • Tertiary carbocations<\/strong> are more stable than secondary, which are more stable than primary.<\/li>\n\n\n\n
    • Allylic and benzylic carbocations<\/strong> are stabilized by resonance.<\/li>\n\n\n\n
    • Better leaving groups<\/strong> (like I\u207b is better than Br\u207b) also favor E1, but carbocation stability dominates.<\/li>\n<\/ul>\n\n\n\n

      Now, consider each compound:<\/p>\n\n\n\n

        \n
      • Compound I<\/strong>: Might form a primary or secondary carbocation (less stable).<\/li>\n\n\n\n
      • Compound II<\/strong>: Possibly forms a secondary carbocation.<\/li>\n\n\n\n
      • Compound III<\/strong>: Likely forms a tertiary carbocation<\/strong>, which is the most stable type.<\/li>\n\n\n\n
      • Compound IV<\/strong>: May form a benzylic or allylic carbocation, which is also stable, but not as much as a well-substituted tertiary one.<\/li>\n<\/ul>\n\n\n\n

        Also, though iodine (I\u207b) is a better leaving group<\/strong> than bromide (Br\u207b), carbocation stability is the dominant factor<\/strong> in E1 reactions.<\/p>\n\n\n\n

        Therefore, compound III<\/strong>, which forms a tertiary carbocation<\/strong>, is the most reactive substrate<\/strong> in an E1 reaction. Even if another compound has a better leaving group, it won\u2019t surpass the rate advantage provided by a more stable carbocation intermediate.<\/p>\n\n\n\n

        Conclusion<\/strong>: The most reactive substrate<\/strong> in an E1 reaction is III<\/strong> due to its ability to form a tertiary carbocation<\/strong>, which accelerates the rate-limiting step.<\/p>\n\n\n\n

        \"\"<\/figure>\n","protected":false},"excerpt":{"rendered":"

        Which of the following is the most reactive substrate in an E1 reaction? Br Br I II III IV \u039f\u0399 \u039f\u0399\u0399 O III O IV The Correct Answer and Explanation is: Correct Answer: III Explanation To determine which substrate is the most reactive in an E1 reaction, we need to understand the E1 mechanism. E1 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-256371","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/256371","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=256371"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/256371\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=256371"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=256371"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=256371"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}