Question

Whats a Base that is the opposite of Lactic acid and that Base will change a color when coming across lactic acid ?

Answer 1

Lactic acid can be detected by the following qualitative reactions : Interaction with n- oxydiphenylene and sulfuric acid :

With gentle heating lactic acid in concentrated sulfuric acid is initially formed acetaldehyde and formic acid, the latter immediately decomposes :

$$\mathrm{CH_3CH(OH)COOH} \rightarrow \mathrm{CH_3CHO} + \mathrm{HCOOH} (\rightarrow \mathrm{H_2O} + \mathrm{CO})$$

Acetaldehyde reacts with n- oxydiphenylene, and apparently, condensation occurs in the o-position to the OH- group to form a 1,1- di ( hydroxybiphenyl ) ethane :

1,1- di ( hydroxybiphenyl ) etan.PNG

In a solution of sulfuric acid is slowly oxidized in purple product of unknown composition. Therefore, as in the detection of glycolic acid with 2,7- dioksinaftalina in this case occurs reacting an aldehyde with a phenol in which the concentrated sulfuric acid acts as a condensing agent and oxidizing agent. The same color reaction gives $\alpha$- hydroxybutyric acid and pyruvic acid.

Performing reactions: In vitro dry heated for 2 minutes in a water bath at $85^{\circ}\mathrm{C}$ a drop of the test solution with $1\mathrm{ml}$ of concentrated sulfuric acid. Then the mixer was cooled to below $28^{\circ}\mathrm{C}$, was added a small amount of solid n- hydroxybiphenyl and stir several times, allowed to stand for 10-30 minutes. Violet color appears gradually and after a while it becomes more profound. The opening at least $1,5\cdot 10^{-6}\mathrm{g}$ of lactic acid.

Interaction with acidic sulfuric acid solution of potassium permanganate

Performing reactions: In $1\mathrm{ml}$ vial tide lactic acid and then slightly acidified with sulfuric acid solution of potassium permanganate. Heat for 2 minutes on low heat. There is a smell of acetic acid.

$$\mathrm{S3N6O3} + [\mathrm{O}] = \mathrm{C3N4O3} + \mathrm{H_2O} \uparrow$$

The product of this reaction can be S3N4O3 pyruvic acid, which also has the smell of acetic acid.

$$\mathrm{S3N6O3} + [\mathrm{O}] = \mathrm{C3N4O3} + \mathrm{H_2O} \uparrow$$

However pyruvic acid is unstable under normal conditions and rapidly oxidized to acetic acid so that the reaction proceeds according to the overall equation

$$\mathrm{S3N6O3} \ 2 + [\mathrm{O}] = \mathrm{CH_3COOH} + \mathrm{CO_2} \uparrow + \mathrm{H_2O}$$