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Give plausible explanation for each of the following: Why are amines less acidic than alcohols of comparable molecular masses? - CBSE (Science) Class 12 - Chemistry

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Question

Give plausible explanation for each of the following :

Why are amines less acidic than alcohols of comparable molecular masses?

Solution 1

Amines undergo protonation to give amide ion.

`R- NH_2 -> R - bar(N) H + H^(+)`

                         Amide ion

Similarly, alcohol loses a proton to give alkoxide ion.

`R - OH -> R - bar(O) + H^(+)`

Alcohol          Alkoxide ion

In an amide ion, the negative charge is on the N-atom whereas in alkoxide ion, the negative charge is on the O-atom. Since O is more electronegative than N, O can accommodate the negative charge more easily than N. As a result, the amide ion is less stable than the alkoxide ion. Hence, amines are less acidic than alcohols of comparable molecular masses

Solution 2

Loss of proton from an amine gives an amide ion while loss of a proton from alcohol give an alkoxide ion.

R—NH2—>R—NH +H+

R—O —H—>R— O +H+ .

Since O is more electronegative than N, so it wijl attract positive species more strongly in comparison to N. Thus, RO~ is more stable than RNH®. Thus, alcohols are more acidic than amines. Conversely, amines are less acidic than alcohols.

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Solution Give plausible explanation for each of the following: Why are amines less acidic than alcohols of comparable molecular masses? Concept: Amines - Preparation of Amines.
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