Which general formula represents an aldehyde?

Which general formula represents an aldehyde?

• A. R-X
• B. R-CO-R
• C. R-CHO
• D. R-OH

Answer: (C)

Aldehydes are defined by a carbonyl group (C=O) that is bonded to at least one hydrogen. This gives the formyl group -CHO, so the general formula is R-CHO, where R can be any carbon-containing group. The carbonyl carbon has one substituent that is a hydrogen, which is what distinguishes aldehydes from other carbonyl compounds. In contrast, a ketone has two carbon substituents on the carbonyl carbon (R-CO-R), and an alcohol carries a hydroxyl group (-OH) on carbon, while an alkyl halide has a halogen (X) attached (R-X).

Aldehydes are defined by a carbonyl group (C=O) that is bonded to at least one hydrogen. This gives the formyl group -CHO, so the general formula is R-CHO, where R can be any carbon-containing group. The carbonyl carbon has one substituent that is a hydrogen, which is what distinguishes aldehydes from other carbonyl compounds.

In contrast, a ketone has two carbon substituents on the carbonyl carbon (R-CO-R), and an alcohol carries a hydroxyl group (-OH) on carbon, while an alkyl halide has a halogen (X) attached (R-X).