Chemistry Aldehydes & Ketones MDCAT 2015
PMDC Verified Question 80 of 94
Both aldehydes and ketones are planar to the neighborhoods of carbonyl (\( C=O \)) group. Which one of the following bonds is distorted towards the oxygen atoms?
A
\( \pi \) bond of C and O
B
\( \sigma \) bond of C and O
C
\( \sigma \) bond of C and H
D
\( \sigma \) bond of C and C
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: \( \pi \) bond of C and O
Concept:

The carbonyl group (\( >C=O \)) is highly polar due to the electronegativity difference between carbon and oxygen.

Solution:

  • Oxygen is significantly more electronegative than carbon.


  • While both the \( \sigma \) and \( \pi \) bonds are polarized, the electrons in the \( \pi \) bond are held more loosely (side-to-side overlap) compared to the tightly held \( \sigma \) bond electrons (head-to-head overlap).


  • Therefore, the electron cloud of the \( \pi \) bond is strongly distorted (pulled) towards the highly electronegative oxygen atom, creating a permanent dipole.


Why other options are incorrect:

The \( \sigma \) bond is more rigid and less polarizable. \( C-H \) and \( C-C \) bonds are virtually non-polar compared to the \( C=O \) bond.

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