{"id":232333,"date":"2025-06-11T23:08:57","date_gmt":"2025-06-11T23:08:57","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=232333"},"modified":"2025-06-11T23:08:59","modified_gmt":"2025-06-11T23:08:59","slug":"choose-the-compound-that-matches-the-ir-spectrum-shown","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/06\/11\/choose-the-compound-that-matches-the-ir-spectrum-shown\/","title":{"rendered":"Choose the compound that matches the IR spectrum shown"},"content":{"rendered":"\n

Choose the compound that matches the IR spectrum shown: 100 = Kw L 50 68 0 4000 3500 3000 2500 2000 1500 Wavenumber (cm\u00e2\u0081\u00bb\u00c2\u00b9) 1000 500 A: B: HO D: E: F: OH The spectrum belongs to compound (select)<\/p>\n\n\n\n

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

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

An analysis of the provided IR spectrum reveals several key absorption bands that are crucial for identifying the unknown compound.<\/p>\n\n\n\n

    \n
  1. O-H Stretch (Carboxylic Acid):<\/strong>\u00a0The most prominent feature of this spectrum is the extremely broad and strong absorption band that dominates the region from approximately 3600 cm\u207b\u00b9 down to 2500 cm\u207b\u00b9. This exceptionally wide peak is the hallmark of the O-H stretching vibration in a hydrogen-bonded carboxylic acid dimer. The broadness is caused by the extensive hydrogen bonding between two acid molecules. This single feature strongly suggests the presence of a \u2013COOH group.<\/li>\n\n\n\n
  2. C=O Stretch (Carbonyl):<\/strong>\u00a0There is a very strong and sharp absorption peak located at approximately 1710 cm\u207b\u00b9. This peak falls squarely in the carbonyl region (1650-1850 cm\u207b\u00b9) and is characteristic of the C=O stretch of a saturated carboxylic acid. The combination of this peak with the aforementioned broad O-H stretch is definitive evidence for a carboxylic acid functional group.<\/li>\n\n\n\n
  3. C-H Stretch (Alkyl):<\/strong>\u00a0The spectrum shows several sharp peaks just below 3000 cm\u207b\u00b9 (in the range of 2850-2960 cm\u207b\u00b9). These are characteristic of C-H stretching vibrations from sp\u00b3-hybridized carbon atoms, indicating the presence of an alkyl (alkane) portion in the molecule.<\/li>\n<\/ol>\n\n\n\n

    Now let’s evaluate the given options:<\/p>\n\n\n\n

      \n
    • A (Alkene):<\/strong>\u00a0Lacks both the O-H and C=O groups.<\/li>\n\n\n\n
    • B (Aromatic hydrocarbon):<\/strong>\u00a0Lacks both the O-H and C=O groups.<\/li>\n\n\n\n
    • C (Ether):<\/strong>\u00a0Lacks both the O-H and C=O groups.<\/li>\n\n\n\n
    • D (Ester):<\/strong>\u00a0Contains a C=O group but lacks the O-H group. An ester C=O stretch typically appears at a higher wavenumber (~1740 cm\u207b\u00b9).<\/li>\n\n\n\n
    • E (Alcohol):<\/strong>\u00a0Contains an O-H group, which would show a broad peak around 3200-3600 cm\u207b\u00b9, but it would not be as exceptionally broad as the one observed. More importantly, it lacks a C=O group.<\/li>\n\n\n\n
    • F (Carboxylic Acid):<\/strong>\u00a0This compound, pentanoic acid, possesses a carboxylic acid group (\u2013COOH) and an alkyl chain. It would exhibit all the characteristic peaks seen in the spectrum: the very broad O-H stretch, the strong C=O stretch around 1710 cm\u207b\u00b9, and the sp\u00b3 C-H stretches below 3000 cm\u207b\u00b9.<\/li>\n<\/ul>\n\n\n\n

      Based on this analysis, the spectrum perfectly matches the expected absorptions for pentanoic acid.<\/p>\n\n\n\n

      The spectrum belongs to compound (F).<\/strong><\/p>\n\n\n\n

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

      Choose the compound that matches the IR spectrum shown: 100 = Kw L 50 68 0 4000 3500 3000 2500 2000 1500 Wavenumber (cm\u00e2\u0081\u00bb\u00c2\u00b9) 1000 500 A: B: HO D: E: F: OH The spectrum belongs to compound (select) The Correct Answer and Explanation is: An analysis of the provided IR spectrum reveals several key […]<\/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-232333","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/232333","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=232333"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/232333\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=232333"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=232333"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=232333"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}