Compound a, c8h10, undergoes nitration to give 2 products. The 1h nmr spectrum of a shows a complex five-proton multiplet at 7.27-7.40 δ, a two-proton quartet at 2.60 δ, and a three-proton triplet at 1.25 δ. What is the structure of a?

1) The presence of multiplet signal ranging from δ 7.27 to 7.40 ppm confirms the presence of aromatic protons. Also the statement says that this signal is for 5 protons indicating that the benzene ring is mono substituted.

2) The substituted group on benzene is Ethyl because the quartet for two protons shows that two protons (-CH₂-) are coupled with a CH₃ group. Hence, the ethyl group gives one quartet and one triplet signal.

3) The chemical reaction stated in statement is Nitration reaction. Also, the alkyl group (ethyl) is ortho-para directing in nature. Hence, it will give two products i.e. 1-Ethyl-2-nitrobenzene and 1-Ethyl-4-nitrobenzene respectively.

Attached figure gives the calculated NMR spectrum of Ethylbenzene and the chemical shifts calculated are almost near to the given values. Also, the two products formed are shown.