Amino acids are classified as acidic, basic or neutral depending upon the relative number of amino and carboxyl groups in their molecule. Which of the following are acidic?

Options

A. `(CH_(3))_(2)CH-underset(" "NH_(2))underset(|)(CH)-COOH`
B. `HOOC-CH_(2)-CH_(2)-underset(" "NH_(2))underset(|)(CH)-COOH`
C. `H_(2)N-CH_(2)-CH_(2)-CH_(2)-COOH`
D. `HOOC-CH_(2)-underset(" "NH_(2))underset(|)(CH)-COOH`

Answer

B, D

Explanation

(b) `HOOC-CH_(2)-CH_(2)-underset(" "NH_(2))underset(|)(CH)-COOH`
Number of COOH group = 2
Number of `NH_(2)` group = 1
Since, number of `COOH` groups `(2) gt` number of `NH_(2)` group (1). Thereofore this amino acid is acidic amino acid.
(d) `HOOC- CH_(2)-underset(" "NH_(2))underset(|)(CH)-COOH`
Number of `COOH` groups = 2
Number of `NH_(2)` groups=1
Since, Number of `COOH` groups `(2) gt` Number of `NH_(2)` groups (1). Therefore, amino acid is acidic. While other two are neutral amino acid as number of `NH_(2)` group in equal to number of `COOH` group in then.