Aldehydes are more reactive than ketones towards nucleophilic addition because in a ketone
Correct answer: B. two alkyl groups release electron density towards the carbonyl carbon and also hinder attack
- A. the carbonyl group is absent
- B. two alkyl groups release electron density towards the carbonyl carbon and also hinder attack
- C. the carbonyl carbon carries a full positive charge
- D. the carbon to oxygen bond is much longer
Explanation
Alkyl groups push electron density towards the carbonyl carbon, reducing its positive character, and their bulk physically blocks the approaching nucleophile, so two of them make a ketone markedly less reactive than an aldehyde with only one. Methanal, having none at all, is the most reactive carbonyl compound of the series. Both electronic and steric factors point the same way here.
Report an error
The more specific you are, the faster it gets fixed. A source beats an opinion.
Prefer email? support@testustad.com
About Reactivity of Aldehydes and Ketones
The polar carbonyl group makes aldehydes and ketones undergo nucleophilic addition, reduction and condensation reactions. Aldehydes are generally more reactive and oxidise readily to carboxylic acids, whereas ketones resist mild oxidation; reactions with hydrogen cyanide, sodium bisulfite and 2,4-DNP help identify their behaviour.
Practise Aldehydes and Ketones
679 free Aldehydes and Ketones MCQs from Chemistry, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Discussion
Stuck on an option, or know a faster way to get there? Ask or explain it here.
No comments yet. Be the first to explain this one.
Exams that ask Chemistry questions like this
Chemistry is on 14 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
More Reactivity of Aldehydes and Ketones questions
The carbonyl carbon of an aldehyde or ketone is attacked by nucleophiles because
Tollens reagent, ammoniacal silver nitrate, gives a silver mirror with
Fehling's solution is reduced to a red precipitate of copper one oxide by
Aldehydes and ketones both react with 2,4-dinitrophenylhydrazine to give
Which compound gives a positive iodoform test?