Question

A compound, C9H12, shows an IR peak at 750 cm-1. Its 1H NMR spectrum has peaks at delta 7.1 (4 H, broad singlet), 2.6 (2 H, quartet, J=8 Hz), 2.3 (3 H, singlet), and 1.2 (3 H, triplet, J=8 Hz). Draw its structure in the window below.

Answer 1

Solution :-

Hydrocarbon with 9 carbon will have (9*2)+2 = 20 hydrogens

but we only have 12 hydrogens

so the number of hydrogen defficiency = 20 - 12 = 8

number of unsaturations = 8/2 = 4

4 H shown peak at 7.1 ppm means they are aromatic protons.

2H shows quartet ar 2.6 ppm means they are CH2 protons attached to CH3 group,

3H shows triplet at 1.2 ppm means they are CH3 protons attached to CH2 because the coupling constants are also same for both.

another 3 H shows singlet at 2.3 ppm means its CH3 group attached to ring.

Following is the possible structure of the compound.