The expected changes in the IR spectra when the conversion of a carboxylic acid to an ester is successful are:
- Loss of sharp peak around 1700 cm-1
- Loss of weak peak around 2200 cm-1
- Loss of broad peak around 3000 cm-1
When the conversion of a carboxylic acid to an ester is successful, several changes can be expected in the infrared (IR) spectra. Let's analyze each option to determine the correct changes:
a. Loss of sharp peak ~1700cm-1: This is correct. Carboxylic acids typically exhibit a sharp peak around 1700 cm-1, which corresponds to the carbonyl stretch of the carboxylic acid functional group. In the formation of an ester, this peak is expected to disappear.
b. Appearance of new sharp peak ~1700cm-1: This is incorrect. The formation of an ester does not result in the appearance of a new sharp peak around 1700 cm-1. Instead, the peak at this region disappears.
c. Appearance of new broad peak ~3000cm-1: This is incorrect. The formation of an ester does not result in the appearance of a new broad peak around 3000 cm-1. The broad peak around 3000 cm-1 is typically associated with the stretching vibration of the O-H bond in carboxylic acids, which is absent in esters.
d. Loss of weak peak around 2200cm-1: This is correct. Carboxylic acids may exhibit a weak peak around 2200 cm-1, which corresponds to the C≡C triple bond. In the formation of an ester, this weak peak is expected to disappear.
e. Loss of broad peak ~3000cm-1: This is correct. Carboxylic acids typically exhibit a broad peak around 3000 cm-1, which corresponds to the stretching vibration of the O-H bond. In the formation of an ester, this broad peak is expected to disappear since esters do not have an O-H bond.
f. Loss of new weak peak around 2200cm-1: This is incorrect. The formation of an ester does not result in the loss of a new weak peak around 2200 cm-1 since there is no new weak peak associated with esters.