Question

When fish is no longer fresh, it often has an unpleasant odor (it is said to smell fishy). This odor is caused by amines (e.g. ethylamine) that are produced when fish begin to deteriorate. Cooks often add vinegar (which is 5% acetic acid) or lemon juice which contains citric and ascorbic acids to minimize this odor. How do you think these acids reduce this fishy odor? Give chemical reactions.

Answer 1

Ehtylamine has a boiling point of 17 degree celsius. So this compound is volatile and has unpleasant odour. So we can make this less volatile by making it to react with an natural acids (vinegar, citric acid or ascorbic acid). This reaction is acid base reaction which gives ammonium salt. Ammonium salts are not volatile and hence reduces the odour.

Reaction:

amine + acid --------> salt + water.

With Vinegar:

CH₃CH₂NH₂ + CH₃COOH -----------> CH₃CH₂NHCOCH₃ + H₂O.

With Citric acid:

CH₃CH₂NH₂ + C₃H₅O(COOH)3--------->CH₃CH₂NHCOCH(COOH)2OC3H5 + H2O

With Ascorbic Acid:

CH₃CH₂NH₂ + C₆H₈O₆ ----------------> CH₃CH₂NHCOC₆H₇O₅ + H₂O.