{"id":231241,"date":"2025-06-10T17:52:35","date_gmt":"2025-06-10T17:52:35","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=231241"},"modified":"2025-06-10T17:52:37","modified_gmt":"2025-06-10T17:52:37","slug":"if-cn-is-a-lewis-base-can-it-also-act-as-a-lewis-acid","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/06\/10\/if-cn-is-a-lewis-base-can-it-also-act-as-a-lewis-acid\/","title":{"rendered":"If CN^ – is a Lewis base, can it also act as a Lewis acid"},"content":{"rendered":"\n

If CN^ – is a Lewis base, can it also act as a Lewis acid?<\/p>\n\n\n\n

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

Expand to view model thoughtschevron_righteditmore_vert<\/p>\n\n\n\n

Correct Answer<\/strong><\/h3>\n\n\n\n

No, the cyanide ion (CN\u207b) cannot act as a general Lewis acid in typical chemical reactions. Its fundamental and overwhelmingly dominant chemical character is that of a Lewis base. However, in the specialized context of coordination chemistry, it can function as an electron pair acceptor in a specific type of interaction known as \u03c0-backbonding.<\/p>\n\n\n\n

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

A Lewis base is defined as a chemical species capable of donating a pair of electrons to form a covalent bond. The cyanide ion, with its molecular structure :C\u2261N:\u207b, is a classic example of a strong Lewis base. The negative formal charge resides primarily on the carbon atom, which possesses a highly accessible and reactive lone pair of electrons. This lone pair is readily donated to a Lewis acid, such as a proton (H\u207a) to form hydrocyanic acid (HCN) or a metal cation (like Fe\u00b2\u207a) to form stable coordination complexes such as hexacyanoferrate(II), [Fe(CN)\u2086]\u2074\u207b. In these interactions, CN\u207b is unambiguously the electron pair donor.<\/p>\n\n\n\n

Conversely, a Lewis acid is a species that can accept a pair of electrons. Typical Lewis acids possess an incomplete electron octet (e.g., BF\u2083) or have low-energy, empty atomic orbitals available to accommodate an incoming electron pair (e.g., transition metal ions). The cyanide ion does not meet these criteria. Both the carbon and nitrogen atoms have a complete valence shell of eight electrons, and there are no low-energy, vacant atomic orbitals to accept an electron pair from another base in a standard acid-base reaction.<\/p>\n\n\n\n

The nuance arises in its role as a ligand in coordination chemistry. While CN\u207b first acts as a Lewis base by donating its lone pair to a metal’s empty orbital (a \u03c3-bond), it can then exhibit Lewis acidic character. The triple bond in CN\u207b has associated empty, high-energy antibonding molecular orbitals (\u03c0* orbitals). If bonded to an electron-rich transition metal (typically one in a low oxidation state), the metal can donate electron density from its filled d-orbitals back into these empty \u03c0* orbitals of the cyanide ligand. In this specific interaction, called \u03c0-backbonding, the cyanide ion is the acceptor<\/em> of electron density, thereby fulfilling the definition of a Lewis acid. This back-donation strengthens the metal-ligand bond and is crucial for the stability of many organometallic complexes.<\/p>\n\n\n\n

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

If CN^ – is a Lewis base, can it also act as a Lewis acid? The Correct Answer and Explanation is: Expand to view model thoughtschevron_righteditmore_vert Correct Answer No, the cyanide ion (CN\u207b) cannot act as a general Lewis acid in typical chemical reactions. Its fundamental and overwhelmingly dominant chemical character is that of a […]<\/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-231241","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/231241","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=231241"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/231241\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=231241"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=231241"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=231241"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}