Which one among the following compounds has a sweet and fruity smell?
- (a)Ethyl alcohol
- (b)Acetic acid
- (c)Ethyl acetate
- (d)Acetophenone
Correct — C, ethyl acetate. Ethyl acetate is an ester (CH3COOC2H5), formed by reacting acetic acid with ethyl alcohol, and esters are precisely the family of organic compounds responsible for the sweet, fruity aromas of ripening fruits and of many perfumes and flavourings. So the compound with a sweet and fruity smell is ethyl acetate.
- (a)Ethyl alcohol — Ethanol has a sharp, spirituous smell, not a sweet fruity one; it belongs to the alcohols, not the ester family that gives fruity odours.
- (b)Acetic acid — Acetic acid is the acid in vinegar and has a pungent, sour, vinegar-like smell — the opposite of a pleasant fruity aroma.
- (d)Acetophenone — Acetophenone is an aromatic ketone with a sweetish, heavy orange-blossom/almond-like odour used in perfumery, but the compound singled out for a characteristically light, fruity smell is the ester, ethyl acetate.
Different families of carbon compounds have characteristic smells. Esters — made by reacting a carboxylic acid with an alcohol — are the sweet, fruity-smelling compounds that occur naturally in fruits and flowers and are widely used as artificial flavours and in perfumes. Ethyl acetate is a simple ester made from acetic acid and ethanol.
Sort the options by chemical family and its typical odour. Alcohols smell sharp, carboxylic acids smell sour and pungent, ketones vary, and esters are the sweet, fruity ones. Only ethyl acetate is an ester, so it is the one carrying the fruity smell.
- Esters form by esterification — a carboxylic acid reacts with an alcohol, usually with a little concentrated sulphuric acid as catalyst.
- Ethyl acetate comes from acetic acid plus ethanol; it is a common solvent and contributes to fruity flavourings and to the smell of many nail-varnish removers.
- Acetic acid gives vinegar its sour, pungent smell, while ethanol has a characteristic spirit-like smell.
- Because they smell pleasant, esters are used as artificial fruit essences and in perfumes.
- Assuming any pleasant-smelling molecule is an ester — acetophenone, a ketone, also smells sweet.
- Confusing acetic acid (pungent vinegar smell) with its ester (fruity).
- Mixing up ethyl alcohol (ethanol) and ethyl acetate.
NDA/UPSC ask which compound or family is fruity-smelling, or to match an ester with its use as a flavour or perfume.
No directly related past PYQ was found.
- practice — not a real PYQ
Esters are generally prepared by the reaction of an alcohol with a
- (a)ketone
- (b)carboxylic acid
- (c)hydrocarbon
- (d)metal oxide
Answer(b) carboxylic acid — an acid reacting with an alcohol (esterification) gives an ester and water.
- practice — not a real PYQ
The pungent smell of vinegar is due to the presence of
- (a)ethanol
- (b)ethyl acetate
- (c)acetic acid
- (d)acetone
Answer(c) acetic acid — vinegar is a dilute solution of acetic acid, which has a sharp sour smell.