Chemistry Aldehydes & Ketones UHS 2024
PMDC Verified Question 1 of 94
\( C_nH_{2n}O \) is the general formula of:
A
Ether
B
Ketones
C
Carboxylic acid
D
Carbolic Acid
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Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Ketones
Concept:

A homologous series is defined by a distinct general formula determined by its functional group and degree of unsaturation.

Solution:

  • A fully saturated, non-cyclic organic molecule with one oxygen (like an ether or alcohol) follows the formula \( C_nH_{2n+2}O \).


  • The formula \( C_nH_{2n}O \) lacks two hydrogens, implying exactly one double bond.


  • In aliphatic carbonyls, this is the \( C=O \) double bond.


  • Therefore, the formula perfectly describes aliphatic Ketones (and Aldehydes).


Why other options are incorrect:

Ethers (\( C_nH_{2n+2}O \)) have no double bonds. Carboxylic acids (\( C_nH_{2n}O_2 \)) have two oxygens. Carbolic acid (Phenol, \( C_6H_6O \)) has a highly unsaturated aromatic ring.

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