1.

Aqueous solution of which of the following amino acids will be basic?A. SerineB. LysineC. LeucineD. Glutamine

Answer» Correct Answer - B
Because it is a basic amino acid, due to the presence of a basic site in its side chain:
`H_(2)N-underset((CH_(2))_(4)NH_(2))underset(|)overset(COOH)overset(|)(C)-H`
There are two possible dipolar structures for Lysine
`underset((I))underset(NH_(2))underset(|)(H_(3)overset(+)(N)(CH_(2))_(4))CHCOO^(-) " " underset((II))underset(.^(+)NH_(3))underset(|)(H_(2)N(CH_(2))_(4)C)HCOO^(-)`
The `-COO^(-)` group is electron - withdrawing and hence base-weakening. The more distant `in`-amino group is affected less, hence, it is more basic, and gets the proton. Thus, `(I)` is the actual sturcture for lysine.


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