Question

Question: Propose possible structure consistent with each set of data. Assume each compound has ${\mathbf{sp}}^{\mathbf{3}}$hybridized C-H absorption in its IR spectrum, and that other major IR absorption above 1500${\mathbf{cm}}^{\mathbf{-}\mathbf{1}}$are list.

1. A compound having a molecular ion at 72 and an absorption in its IR spectrum at 1725 ${\mathbf{cm}}^{\mathbf{-}\mathbf{1}}$.
2. A compound having a molecular ion at 55 and an absorption in its IR spectrum at 2250 ${\mathbf{cm}}^{\mathbf{-}\mathbf{1}}$.
3. A compound having a molecular ion at 74 and an absorption in its IR spectrum at 3600-3200 ${\mathbf{cm}}^{\mathbf{-}\mathbf{1}}$.

Short answer

Answer

a. Molecular ion peaks at 72 and IR peaks at 1725 ${\mathrm{cm}}^{-1}$; the possible structure is-

2-butanone

b. Molecular ion peaks at 55 and IR peaks at approximately 2250 ${\mathrm{cm}}^{-1}$; the possible structure is

propionitrile

c. Molecular ion peaks at 74 and IR peaks at 3600-3200 ${\mathrm{cm}}^{-1}$; the possible structures are as shown below:

alcohols

Step-by-step solution

Molecular ion peak

The molecular ion peak indicates the m/z value in mass spectra, and the base peak is the most intensive peak.The molecular ion peak is the highest in mass spectra, indicating the greatest relative abundance.

Functional group identification

a. Molecular ion peaks at 72 and IR peaks at 1725 ${\mathrm{cm}}^{-1}$, indicating the presence of the carbonyl group.

2-butanone

b. Molecular ion peaks at 55 and IR peaks at approximately 2250 ${\mathrm{cm}}^{-1}$, then is present.

propionitrile

c. Molecular ion peaks at 74 and IR peaks at 3600-3200 ${\mathrm{cm}}^{-1}$, then the hydroxyl group is present.

Alcohols