Question

Below are six infrared IR Spectra for the following compounds.Determine which IR fits which structure. Indicate the diagnostic bands you used to differentiate between the six compounds, draw your answer in the box on the right along with the appropriate name, and the reasoning for your answer in the box provided.
1. Below are six Infrared (IR) Spectra for the following compounds. Determine which IR fits which structure. Indicate the diagnostic bands you used to differentiate between the six compounds, draw your answer in the box on the right along with the appropriate name, and the reasoning for your answer in the box provided. Names: butanal, butanoic acid, methyl acrylate, 2-pentanol, 2-pentanone, 4-penten-2-ol OH voi mom m Compound Name: 1468 Compound Structure: 2960 1706 - HEN Missing wavenumbers at the dashes are 1368 & 1172 Reasoning

Answer 1

1. First spectrum is of 2-pentanone.
   Reasoning : It shows a ketone C=O stretching vibration band at 1706 cm-Absorption near 1368 shows presence of CH3-CO group. Peak near 1172 cm-1 indicates presence of C-CO-C stretching and bending vibration. Absorption near 2960 indicates presence of aliphatic C-H stretching vibrations.
   Thus, there is methyl keto group and aliphatic C-H groups indicating presence of 2-pentanone.
   
   2-pentanone
   
   
   
2. Second spectrum is of butyraldehyde.
   Reasoning: It shows absorption at 1729 indicating presence of carbonyl C=O group stretching vibrations. Small peak near 2725 indicates presence of aldehydic C-H stretching vibrations. Thus, aldehyde functional group is present. Absorption near 2966 indicates presence of aliphatic C-H stretching vibrations. Weak absorption near 1468 indicates aliphatic C-H bending vibrations.
   Thus, there is aldehyde functional group in the molecule indicating presence of butyraldehyde.
   
   H butyraldehyde
   
   
3. Third spectrum is of 4-penten-2-ol.
   Reasoning: Third IR spectrum shows broad absorption near 3359 indicating presence of hydroxyl group. Medium absorption at 3042 indicates presence of alkene C-H stretching vibrations. Strong absorption at 2963 indicates alkane C-H stretching vibrations. Peak at 1655 indicates alkene C=C stretching vibrations. Strong peaks near 1100 indicates presence of C-O stretching vibrations. Absorption near 1468 indicates aliphatic C-H bending vibrations.
   Thus, there is hydroxyl and alkene functional group indicating presence of 4-penten-2-ol.
   
   4-penten-2-ol
   
   
4. Fourth spectrum is of pentan-2-ol.
   Reasoning: Fourth IR spectrum shows strong and broad absorption near 3315 indicating presence of hydroxyl group. Strong absorption near 2975 indicates presence of aliphatic C-H stretching vibrations. Peak at 1473 indicates aliphatic C-H bending vibrations.
   Thus, there is hydroxyl functional group and aliphatic C-H indicating presence of pentan-2-ol.
   
   pentan-2-ol
   
   
5. Fifth spectrum is of methyl acrylate.
   Reasoning: Fifth IR spectrum shows absorption near 3041 indicating alkene C-H stretching vibrations. Absorption near 2945 indicates alkane C-H stretching vibrations. Strong absorption near 1709 indicates carbonyl C=O group stretching vibrations. Strong absorption near 1188 indicates C-O stretching vibrations indicating presence of ester functional group. Peak at 1645 indicates alkene C=C stretching vibrations.
   Thus, there is ester group and alkene C=C, indicating presence of methyl acrylate.
   
   methyl acrylate
   
   
6. Sixth spectrum is of butanoic acid.
   Reasoning: Sixth IR spectrum shows broad absorption from 3500 to 2500 indicating carboxylic acid functional group. Absorption near 2973 indicates presence of aliphatic C-H stretching vibrations. Strong absorption near 1714 indicates carbonyl C=O stretching vibrations. Absorption near 1417 indicates alkane C-H bending vibrations. Peak near 1222 indicates C-O stretching vibrations.
   Thus, there is carboxylic acid functional group and alkyl chain indicating presence of butanoic acid.
   
   HO butanoic acid