# Which compound would be expected to show intense IR absorption at 3363, 3185, 1660 cm-1? How do you know?

## $C {H}_{3} C {H}_{2} C {H}_{2} O H$ ${\left(C {H}_{3}\right)}_{2} C H N {H}_{2}$ $C {H}_{3} C {H}_{2} C O N {H}_{2}$ but-1-ene

May 16, 2016

${\text{CH"_3"CH"_2"CONH}}_{2}$ would be expected to show the observed peaks.

#### Explanation:

Let's eliminate the obvious culprits.

Propan-1-ol would show only a broad band from $\text{3200 - 3550 cm"^"-1}$.

2-Methylpropanamine would not show a peak at $\text{1660 cm"^"-1}$.

But-1-ene would show no peaks above $\text{3100 cm"^"-1}$.

The peak at $\text{1660 cm"^"-1}$ could be either "C=C" ("1620 – 1680 cm"^"-1") or "amide C=O" ("1640 – 1690 cm"^"-1").

The two peaks at $\text{3363 cm"^"-1}$ and $\text{3165 cm"^"-1}$ are definitive, however.

They must represent the symmetric ($\text{~3180 cm"^"-1}$) and asymmetric ("~3350 cm"^"-1")color(white)(l) "N-H" stretches of an amide ${\text{NH}}_{2}$ group.

The compound must be propanamide.