Question

why nitroacetic acid is more acidic then 2 hidrodyacetic acid ​

Answer 1

Answer:

My prediction is that hydroxyl acetic acid (glycolic acid) will be stronger than amino acetic acid (aka, glycine). The reason for this is the the group in the alpha position (-OH or -NH2, respectively) is the only difference, that these groups will exert their effect by induction, and that the electronegativity of ‘O’ is greater than ’N’ (thus stabilizing the carboxylate form with its negative charge).

Explanation:

Unfortunately, my prediction does not agree with reality. The pKas are as follows:

hydroxyl acetic acid (glycolic acid) pKa = 3.7

amino acetic acid (glycine) pKa = 2.34

I think the reason my prediction is off is that the pKa reported for:

(NH3+)-CH2-COOH

and not

(NH2)-CH2-COOH

NH3+ is much more electron withdrawing relative to NH2. However, if you could measure the pKa of

(NH2)-CH2-COOH, I bet it would be between 3.7 and 4.76 (the pKa of acetic acid).

Answer 2

Answer:

This is due to resonance effect.

Explanation:

As look at the structures of both compounds:

First of all, in case if nitroacetic acid there were one negatively charged oxygen forming single bond with nitrogen atom and other oxygen atom forming double bond with that nitrogen atom.

This double and single bond change their position with each other.

Or simply we say, there were a conjugation betwene two oxygen and one nitrogen atom.

Due to this reason they makes the molecule stable.

But,

In case of 2-hydroxyacitic acid:

A hydroxyl OH group present at the place of NO₂ which is itself has a high tendency to accept proton H+.

Thus, 2-hydroxyacitic acid is less acidic, than nitroacetic acid.