Where is the carbonyl group located in a ketone?

Where is the carbonyl group located in a ketone?

• A. Terminal carbon
• B. On a side chain
• C. Middle carbon (C=O)
• D. On a ring carbon

Answer: (C)

The key idea is that in a ketone the carbonyl carbon is bonded to two other carbon atoms, placing the C=O group inside the carbon chain rather than at an end. This internal position is what distinguishes ketones from aldehydes, where the carbonyl carbon is at the terminal position and connected to a hydrogen. For example, in propanone (CH3-CO-CH3) the carbonyl carbon sits between two carbon groups, illustrating the middle location of the C=O in ketones. While a cyclic ketone has the carbonyl on a ring carbon, the standard description of a ketone’s carbonyl location is that the C=O carbon is the middle carbon, bonded to two carbons.

The key idea is that in a ketone the carbonyl carbon is bonded to two other carbon atoms, placing the C=O group inside the carbon chain rather than at an end. This internal position is what distinguishes ketones from aldehydes, where the carbonyl carbon is at the terminal position and connected to a hydrogen. For example, in propanone (CH3-CO-CH3) the carbonyl carbon sits between two carbon groups, illustrating the middle location of the C=O in ketones. While a cyclic ketone has the carbonyl on a ring carbon, the standard description of a ketone’s carbonyl location is that the C=O carbon is the middle carbon, bonded to two carbons.