Question

Compare the rate of reduction with \(\mathrm{NaBH}_{4}\). CC(=O)c1ccccc1 O=Cc1ccc([N+](=O)[O-])cc1 O=Cc1ccccc1 (I) (II) (III) (A) I > II > III (B) II > III > I (C) II > I > III (D) \(\mathrm{III}>\mathrm{II}>\mathrm{I}\)

Short answer

The rate of reduction with NaBH₄ can be compared by examining the electron-donating or withdrawing groups' effect on the carbonyl group reactivity. Acetophenone (I) has an electron-donating methyl group (-CH3) making it more susceptible to reduction; 4-Nitrobenzaldehyde (II) has an electron-withdrawing nitro group (-NO₂), making it less susceptible; Benzaldehyde (III) has no additional groups, lying between the other two. Thus, the correct order of rate of reduction is I > III > II or (A) I > II > III.

Step-by-step solution

Convert SMILES notations to chemical structures

Use an appropriate tool or software to draw the structures of the compounds from the given SMILES notations: (I) CC(=O)c1ccccc1 - Acetophenone (II) O=Cc1ccc([N+](=O)[O-])cc1 - 4-Nitrobenzaldehyde (III) O=Cc1ccccc1 - Benzaldehyde

Examine the functional groups

Take note of the functional groups present in each compound, which are affected by reduction using NaBH₄. The primary functional group that undergoes reduction in all three structures is the carbonyl group, C=O.

Analyze the effect of different groups on the rate of reduction

The electron-donating or withdrawing groups on the aromatic ring have a significant influence on the rate of reduction. Electron-donating groups activate the carbonyl group and make it more susceptible to reduction. Conversely, electron-withdrawing groups deactivate the carbonyl group and make it less susceptible to reduction. In the given compounds: - Acetophenone (I) has an electron-donating methyl group (-CH3) at the alpha position. - 4-Nitrobenzaldehyde (II) has an electron-withdrawing nitro group (-NO₂) at the para position. - Benzaldehyde (III) has no additional electron-donating or withdrawing groups.

Determine the relative rates of reduction

Compare the structures considering the electron-donating or withdrawing groups present: - Acetophenone (I) has an electron-donating group, making it easier to reduce. - 4-Nitrobenzaldehyde (II) has an electron-withdrawing group, making it harder to reduce. - Benzaldehyde (III) lies somewhere in between as it has neither an electron-donating nor an electron-withdrawing group. Thus, the correct order for the rate of reduction is Acetophenone > Benzaldehyde > 4-Nitrobenzaldehyde, or I > III > II.

Choose the correct option

Based on our analysis, the correct order of the rate of reduction is I > III > II. Therefore, the correct option is (A)I > II > III.