Question

Compound A, C₄H₈O₃, has infra-red absorptions at 1710 and 2500 to 3100 cm^-1 and has the ¹H NMR spectrum shown. Propose a structure for A.

Short answer

The compound is 2-Ethoxyethanoic acid

Step-by-step solution

Infrared and NMR spectrum

An Infrared spectrum helps to study and identify chemical substances and functional groups in compounds.

NMR stands for nuclear magnetic resonance spectrum, which helps to determine the molecular structure and chemical composition of an organic compound.

Conclusion from the infrared spectrum.

According to the infrared spectrum, absorption lies at a range of 1710 and 2500 to 3100cm^-1. The peak at 1710 indicates a presence of the Carbonylgroup of carboxylic acid and the range 2500 to 3100 cm^-1 indicates the hydroxyl group of carboxylic acid.

Conclusion from the NMR spectrum.

According to the NMR spectrum, the signal at 1.26ppm indicates the presence of a methyl group that is attached to the methylene group, as the three hydrogen atoms will give a triplet following the (n+l) rule, where n is the number of hydrogen atoms present in adjacent carbon.

The quartet of two hydrogen atoms at 3.64 ppm indicates the presence of a methylene group adjacent to the methyl group.

The singlet of the 2 hydrogens indicates that the methylene group does not have any hydrogen atoms in the adjacent position.

The signal at 11.1ppm indicates the hydrogen of the carboxylic group.

Result:

Hence, compound A is 2-Ethoxyethanoic acid.

The structure of the compound is: