Amino acids are

Options

A. nonpolar
B. amphoteric
C. acidic
D. basic

Answer

B

Explanation

Amino acids undergo internal acid has reaction to form dipolar ion or zwitterion:
`RCHoverset(+)((NH_(3)))COO^(-)`
In zwitteronic form, amino acids show amphoteric behaviour as they react the both with acids and bases, In acidic solution the carboxylate the function `(-COOH^(-))` accepts a proton and gets converted to carboxyl substituent,
`H_(3) overset(+)NCHRCOO^(-) overset(H^(+))rarr H_(3) overset(+)NCHRCOOH`
While in basic solution the ammonium substituent `overset(+)((NH_(3)))`change to amino group `(-NH_(2))` by losing a proton
`H_(3) overset(+)NCHRCOO^(-)overset(OH^(-))rarr H_(2) NCHRCOO^(-)`
The crystal structure of `alpha`-amino acid, existing as dipolar ions, is a consequence of the strong intermolecular electrostatic attractive forces. and unlike uncharged molecules of the same molecular mass, most `A A's` decompose rather than melt. Owing to their dilopar structure, most `A A's` are appreciably soluble in water (forming H - bonds and ion-diplole bonds) and insoluble in nonpolar of aprotic solvents. In quite alkaline solution, an amino acid cantains two basic groups, `-NH_(2)` and `COO^(-)`. The former is more basic, therefore, a proton preferertially goes to `NH_(2)` as acid is added to the solution:
`H_(2) NCHRCOO^(-) + H^(+) rarr H_(3) overset(+)NCHRCOO^(-)`
In quite acidic solution, an amino acid contains two acidic groups, `-underset(+)NH_(3)` and `- COOH`. The latter is more acidic, therefore, `COOH` group more readily gives up a proton as base is added to the solution
`H_(3) overset(+)NCHRCOOH overset(OH^(-))rarr H_(2) O + H_(3) overset(+)NCHRCOO^(-)`