Question

Isoamyl acetate is the primary component of artificial banana flavor. Which signals will be in the positive phase, negative phase, or nonexistent in normal 13C NMRof isoamyl acetate?

Answer 1

Ans.

The structure of isoamyl acetate is shown below.

In a proton decoupled C13 NMR, there will be six signals due to six Cs in different chemical environment.

In DEPT 45, signals for carbons in CH, CH₂ and CH₃ will be positive. So, there will be five signals and there will be no signal for carbon numbered (e).

DEPT 90 shows positive signal only for CH groups. So, in DEPT 90 only carbon numbered (b) will show a positive signal. Other carbons will not show any signal in DEPT 90.

DEPT 135 shows positive signal for CH and CH₃ groups and negative signal for CH₂ group. So in DEPT 135, carbons numbered (a), (b) and (f) will show a positive signal. Carbons numbered (c) and (d) will show negative signal. Carbon numbered (e) will not show any peak in DEPT 135.