Question

22. Of the following lowest Pka
value
Chloroacetic acid
O Cyanoacetic acid
O bromoacetic acid
O Nitroacetic acid​

Answer 1

Answer:

Low pKa means they are asking for stronger acid,

this will work on the principle of conjugate base, the more stronger the acid is, the weaker/stable  is its conjugate base.

here all are electron withdrawing groups which will pull and delocalize the electron of the conjugate base of substituted acetic acid and make it more stable.

The electron withdrawing tendecy/ base stabilising tendency/imparting more acidic character tendency are in this order:-

-NO2>-CN>-Cl>-Br