Give plausible explanation for each of the following :
Why are amines less acidic than alcohols of comparable molecular masses?
Amines undergo protonation to give amide ion.
`R- NH_2 -> R - bar(N) H + H^(+)`
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
Loss of proton from an amine gives an amide ion while loss of a proton from alcohol give an alkoxide ion.
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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- Amines - Preparation of Amines