Q82E - Organic Chemistry (Mcmurry)

Question

The ¹HNMR   spectrum shown is that of a compound isomeric with the one in Problem 19-81. This isomer has an IR absorption at 1730 cm^-1. Propose a structure.

[Note: Aldehyde protons (CHO) often show low coupling constants to adjacent hydrogens, so the splitting of aldehyde signals is not always apparent.]

Step-by-Step Solution

Answer

The structure of the compound is:

Step 1: Identify compound from IR

As the IR peak is observed at 1730 cm^-1 so the compound must be an aldehyde and the aldehyde proton show low so, it is not in conjugation with the aromatic rings.

Step 2: Identify compound from NMR

As per the graph, it is seen that the triplet is produced by the methylene group which means the two methylene groups are adjacent to each other and aldehyde is present at the terminal and the peak at 9.82 shows the presence of the aromatic ring so, the compound must be: