{"id":41615,"date":"2025-06-28T09:47:02","date_gmt":"2025-06-28T09:47:02","guid":{"rendered":"https:\/\/gaviki.com\/blog\/?p=41615"},"modified":"2025-06-28T09:47:03","modified_gmt":"2025-06-28T09:47:03","slug":"the-infrared-ir-spectrum-of-an-organic-compound-is-shown-below","status":"publish","type":"post","link":"https:\/\/gaviki.com\/blog\/the-infrared-ir-spectrum-of-an-organic-compound-is-shown-below\/","title":{"rendered":"The infrared (IR) spectrum of an organic compound is shown below"},"content":{"rendered":"\n

The infrared (IR) spectrum of an organic compound is shown below % Transmittance 100 50 0 4000 3000 2000 1500 1000 500 Wavenumber \/ cm
(d) Deduce the structures of two possible isomers of propanoic acid consistent with the IR spectrum.<\/p>\n\n\n\n

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

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

To answer part (d) \u2014 deducing two possible isomers of propanoic acid consistent with the IR spectrum \u2014 we must first analyze the spectrum provided and identify the key absorption peaks that indicate functional groups present.<\/p>\n\n\n\n

Key IR Peaks and Interpretation:<\/strong><\/h3>\n\n\n\n
    \n
  1. Broad absorption around 2500\u20133300 cm\u207b\u00b9<\/strong>:\n
      \n
    • This is characteristic of the O\u2013H stretch of a carboxylic acid. The broad and irregular shape supports this interpretation.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
    • Sharp peak near 1710 cm\u207b\u00b9<\/strong>:\n
        \n
      • This corresponds to the C=O stretching vibration typical of carboxylic acids.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
      • Multiple peaks in the fingerprint region (below 1500 cm\u207b\u00b9)<\/strong>:\n
          \n
        • These are consistent with various C\u2013H bending vibrations and other molecular features. While not individually diagnostic, they help confirm the molecular structure.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n

          Conclusion:<\/strong><\/h3>\n\n\n\n

          The compound is a carboxylic acid, consistent with propanoic acid (CH\u2083CH\u2082COOH)<\/strong>. Isomers of propanoic acid are compounds with the same molecular formula (C\u2083H\u2086O\u2082) but different structures.<\/p>\n\n\n\n

          Two Possible Isomers Consistent with the IR Spectrum:<\/strong><\/h3>\n\n\n\n
            \n
          1. Propanoic acid (CH\u2083CH\u2082COOH)<\/strong>:\n
              \n
            • A straight-chain carboxylic acid.<\/li>\n\n\n\n
            • Shows both O\u2013H and C=O stretches.<\/li>\n\n\n\n
            • No branching or other functional groups.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
            • 2-hydroxypropanal (CH\u2083CH(OH)CHO)<\/strong>:\n
                \n
              • While technically not a positional isomer of a carboxylic acid, it is a constitutional isomer with the same molecular formula.<\/li>\n\n\n\n
              • Contains an aldehyde (C=O around 1720 cm\u207b\u00b9) and hydroxyl (O\u2013H around 3300 cm\u207b\u00b9).<\/li>\n\n\n\n
              • However, this structure may not match as well due to the absence of a broad, strong carboxylic O\u2013H stretch.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n

                A better second candidate:<\/p>\n\n\n\n

                Methyl formate (HCOOCH\u2083)<\/strong>:<\/p>\n\n\n\n

                  \n
                • An ester, another isomer of C\u2083H\u2086O\u2082.<\/li>\n\n\n\n
                • Esters show a C=O stretch around 1740 cm\u207b\u00b9 and a C\u2013O stretch near 1200 cm\u207b\u00b9.<\/li>\n\n\n\n
                • However, the broad O\u2013H peak is absent in esters, so it’s less likely given the spectrum.<\/li>\n<\/ul>\n\n\n\n

                  Final answer:<\/strong><\/p>\n\n\n\n

                    \n
                  • Propanoic acid (CH\u2083CH\u2082COOH)<\/strong><\/li>\n\n\n\n
                  • 2-hydroxypropanoic acid (lactic acid, CH\u2083CH(OH)COOH)<\/strong> \u2014 a plausible isomer with similar O\u2013H and C=O signals, consistent with the IR spectrum.<\/li>\n<\/ul>\n\n\n\n
                    \"\"<\/figure>\n","protected":false},"excerpt":{"rendered":"

                    The infrared (IR) spectrum of an organic compound is shown below % Transmittance 100 50 0 4000 3000 2000 1500 1000 500 Wavenumber \/ cm(d) Deduce the structures of two possible isomers of propanoic acid consistent with the IR spectrum. The Correct Answer and Explanation is: To answer part (d) \u2014 deducing two possible isomers […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-41615","post","type-post","status-publish","format-standard","hentry","category-quiz-questions"],"_links":{"self":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/41615","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/comments?post=41615"}],"version-history":[{"count":1,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/41615\/revisions"}],"predecessor-version":[{"id":41625,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/41615\/revisions\/41625"}],"wp:attachment":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/media?parent=41615"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/categories?post=41615"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/tags?post=41615"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}