Which term correctly describes the functional group R-CHO?

Which term correctly describes the functional group R-CHO?

• A. Ketone
• B. Aldehyde
• C. Alcohol
• D. Carboxylic acid

Answer: (B)

R-CHO represents an aldehyde. The carbonyl carbon (the C=O) is bonded to one carbon-containing group (the R) and to a hydrogen, which is the hallmark of aldehydes. This terminal position with a hydrogen distinguishes aldehydes from ketones, where the carbonyl carbon is bonded to two carbon groups, not hydrogen. Alcohols have an O-H bond (R-OH), and carboxylic acids have a carbonyl carbon also bonded to a hydroxyl group (R-COOH). Writing as R-CHO explicitly shows the formyl group that defines aldehydes, with common examples like formaldehyde (H-CHO) and acetaldehyde (CH3-CHO).

R-CHO represents an aldehyde. The carbonyl carbon (the C=O) is bonded to one carbon-containing group (the R) and to a hydrogen, which is the hallmark of aldehydes. This terminal position with a hydrogen distinguishes aldehydes from ketones, where the carbonyl carbon is bonded to two carbon groups, not hydrogen. Alcohols have an O-H bond (R-OH), and carboxylic acids have a carbonyl carbon also bonded to a hydroxyl group (R-COOH). Writing as R-CHO explicitly shows the formyl group that defines aldehydes, with common examples like formaldehyde (H-CHO) and acetaldehyde (CH3-CHO).