Q43E - Organic Chemistry (Mcmurry)

Question

Propose structures for compounds that meet the following descriptions:

1. An optically active compound C₅H₁₀O with an IR absorption at 1730 cm^-1 .
2.  A non-optically active compound C₅H₉N with an IR absorption at 2215 cm^-1 . 

Step-by-Step Solution

Answer

IR spectroscopy

All the absorptions seen in alkanes is due to the C-C and C-H bonds. The C-H bonds show absorption in the region 2850 to 2950 cm^-1  and the C-C bonds are seen in the region 800 to 1300 cm^-1.Most of the organic compounds exhibit these absorptions as they comprise saturated alkane portion.

Proposing the structure of the compound with different description

(a)The optically active compound with the formula C₅H₁₀O that absorbs at 1730 cm^-1 can be given as:

                                                  Optically active compound

The IR absorption at this region is due to the saturated aldehyde. The name of the compound is 2-methylbutanal.

(b)The non optically active compound has a formula C₅H₉N  that absorbs at 2215 cm^-1 can be given as:

The absorption at this frequency is due to the cyanide functional group. The given compound is trimethylacetonitrile.