Question

8. How would you use "H NMR to distinruish between the following compounds? (20 points) A. C10c and shows up between 1600-1680 shows up between 3200-3450 and

Answer 1

A. The right hand side molecule will give two singlet signals while the left hand side molecule will give one siglet signal. Thus they can be identified.

Explanation: In the molecule on the left, since it is a symmetrical molecule, the protons are equivalent. On the other hand, the molecule on the right, since it has Cl and Br on each side is not symmetrical and will give two signals.

B. The molecule on the right will give seven peaks (3 feom benzene ring, one from the sp3 carbon and 3 from the hydrogens attached to the double bond) while the molecule will give 5 signals (3 from the ring, one each from hydrogens attached to sp3 carbon and sp carbon). The hydrogens attached to sp2 hybridized carbon in the molecule on the left will have peaks at higher values due to the shielding effect of double bond.

C. The molecule on the left will show characterictic peak at high delta value correspinding to carboxylic acid proton while the molecule on the right will show characteristic peak corresponding to aldehyde proton.

D. Since on the molecule on the left, the -CH2CH3 group is attached to oxygen, the quqrtet signal of CH2 will be have higher delta value. On the molecule on right, the three hydrogens of CH3 group attached to oxygen will have higher delta value for the peak.