{"id":219869,"date":"2025-05-27T06:11:23","date_gmt":"2025-05-27T06:11:23","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=219869"},"modified":"2025-05-27T06:11:25","modified_gmt":"2025-05-27T06:11:25","slug":"h2o-nh2-primary-amines-can-be-prepared-from-nitriles-by-reduction-with-lialh4","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/05\/27\/h2o-nh2-primary-amines-can-be-prepared-from-nitriles-by-reduction-with-lialh4\/","title":{"rendered":"H2O NH2 Primary Amines Can Be Prepared From Nitriles By Reduction With LiAlH4"},"content":{"rendered":"\n

CN 2. LiAIH4 3. H2O NH2 Primary Amines Can Be Prepared From Nitriles By Reduction With LiAlH4. The Two-Step Sequence Involves SN2 Displacement Of Halide Ion By Cyanide Ion Followed By Reduction, And Yields A Primary Amine With One More Carbon Than Was Present In The Alkyl Halide. Draw Curved Arrows To Show The Movement Of Electrons In This Step Of The<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

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

Correct Arrow-Pushing Mechanism (Reduction of Nitrile to Amine using LiAlH\u2084):<\/h3>\n\n\n\n

In the image provided, the mechanism step shown is the reduction of a nitrile (-C\u2261N)<\/strong> by lithium aluminum hydride (LiAlH\u2084)<\/strong>. The curved arrows should show the following steps:<\/p>\n\n\n\n

Correct Arrow Movements:<\/h4>\n\n\n\n
    \n
  1. Nucleophilic attack by hydride (H\u207b)<\/strong> from the AlH\u2084\u207b anion:\n
      \n
    • The hydride attacks the electrophilic carbon of the nitrile group (C\u2261N), breaking one \u03c0 bond of the triple bond.<\/li>\n\n\n\n
    • The electrons from the \u03c0 bond move to the nitrogen, forming an imine anion intermediate.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
    • Second hydride transfer<\/strong>:\n
        \n
      • Another hydride from LiAlH\u2084 attacks the carbon again, reducing the imine to an amine anion.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
      • Coordination to AlH\u2083<\/strong>:\n
          \n
        • The nitrogen donates its lone pair to aluminum, forming a coordinate bond with AlH\u2083 (as shown in the rightmost product).<\/li>\n<\/ul>\n<\/li>\n\n\n\n
        • Final hydrolysis (with H\u2082O)<\/strong> step not shown here, but it would liberate the free primary amine<\/strong> (\u2013NH\u2082) by breaking the Al\u2013N bonds.<\/li>\n<\/ol>\n\n\n\n
          \n\n\n\n

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

          The transformation shown is a classic method to synthesize primary amines<\/strong> using a three-step sequence<\/strong> involving cyanide substitution followed by reduction. The substrate is a benzyl bromide, which undergoes SN2 substitution<\/strong> with cyanide ion (CN\u207b) to form a nitrile intermediate. This nitrile is then reduced by lithium aluminum hydride (LiAlH\u2084)<\/strong>.<\/p>\n\n\n\n

          LiAlH\u2084 is a strong reducing agent that donates hydride ions (H\u207b). In the reduction step, the hydride nucleophilically attacks the electrophilic carbon<\/strong> of the nitrile (C\u2261N), breaking one of the carbon-nitrogen \u03c0 bonds and producing an imine anion intermediate<\/strong>. A second hydride attack further reduces the imine to an amine anion<\/strong>, which is stabilized by coordination to AlH\u2083<\/strong> through the lone pair on nitrogen.<\/p>\n\n\n\n

          The final step (not shown) involves aqueous work-up<\/strong> (addition of water), which hydrolyzes the Al\u2013N bonds to yield the free primary amine<\/strong> product.<\/p>\n\n\n\n

          This process is extremely useful in synthetic organic chemistry because it adds a carbon to the original alkyl halide chain via the cyanide ion and then converts the nitrile into a primary amine. This method is particularly valuable for extending carbon chains while introducing nitrogen functionality.<\/p>\n\n\n\n

          The curved arrow mechanism illustrates the flow of electrons, helping to rationalize the bonding changes that take place during the reaction. Understanding these mechanisms is key to mastering organic synthesis and reaction design.<\/p>\n\n\n\n

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

          CN 2. LiAIH4 3. H2O NH2 Primary Amines Can Be Prepared From Nitriles By Reduction With LiAlH4. The Two-Step Sequence Involves SN2 Displacement Of Halide Ion By Cyanide Ion Followed By Reduction, And Yields A Primary Amine With One More Carbon Than Was Present In The Alkyl Halide. Draw Curved Arrows To Show The Movement […]<\/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-219869","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/219869","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=219869"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/219869\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=219869"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=219869"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=219869"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}