Question

Compare the bond length X, Y and Z in the following compound
Where: (X) is the C=O bond, (Y) is the C-O bond between carbonyl group and oxygen, (Z) is the C-O bond between the oxygen and the methyl group.

• A. X = Y = Z
• B. X = Y < Z
• C. X < Y < Z
• D. X < Y = Z

Hint:

In organic compounds, bond lengths depend on the type of bond (single, double, triple), as well as the inductive effects of surrounding atoms or groups. Electron-withdrawing groups shorten bonds, while electron-donating groups lengthen them.

Answer 1

The Correct Option is C

Step 1: Bond order in the compound.
In the given compound \(\mathrm{H_3C-C(=O)-O-CH_3}\), we have three distinct bonds to compare: - (X) C=O (double bond between carbon and oxygen in the carbonyl group).
- (Y) C-O (single bond between carbonyl group and oxygen).
- (Z) C-O (single bond between the oxygen and methyl group).

Step 2: Bond length comparison.
- The C=O double bond (X) is shorter than the single C-O bonds because a double bond has more electron density between the atoms, pulling them closer together.
- The C-O bond between the carbonyl group and oxygen (Y) is shorter than the C-O bond between oxygen and methyl group (Z). The reason is that the electron-withdrawing carbonyl group causes a greater attraction between carbon and oxygen in the carbonyl bond than between oxygen and the methyl group, which is electron-donating.
Step 3: Conclusion.
Therefore, the bond lengths follow the order: \[ X<Y<Z \] This makes option (C) the correct answer. Final Answer: Option (C) X < Y < Z.