Ninhydrin test is used to estimate the amount of amino acid present in a solution while they are being eluted in an ion exchange chromatography or HPLC. Concept introduction: In the ion-exchange technique, separated amino acids eluting from the chromatography column mix with a solution of a substance called ninhydrin and undergo a rapid reaction that produces an intense purple color. The color is measured by a spectrometer, and a plot of elution time versus spectrometer absorbance is obtained. To determine: The structure and mechanisms involved in the reaction of ninhydrin with α-amino acid.

Question

The reaction of ninhydrin with an -amino acid occurs in several steps (a) The first step is loss of water to give a triketone. Show the mechanism of the reaction and the structure of the triketone.(b) The second step is formation of an imine by reaction of the amino acid with the triketone. Show its structure. (c) The third step is a decarboxylation. Show the structure of the product and the mechanism of the decarboxylation reaction. (d) The fourth step is hydrolysis of an imine to yield an amine and an aldehyde. Show the structures of both products. (e) The final step is formation of the purple anion. Show the mechanism of the reaction

Answer 1

Question

Chapter 26.SE, Problem 24MP

Interpretation Introduction

Interpretation:

Ninhydrin test is used to estimate the amount of amino acid present in a solution while they are being eluted in an ion exchange chromatography or HPLC.

Concept introduction:

In the ion-exchange technique, separated amino acids eluting from the chromatography column mix with a solution of a substance called ninhydrin and undergo a rapid reaction that produces an intense purple color. The color is measured by a spectrometer, and a plot of elution time versus spectrometer absorbance is obtained.

To determine:

The structure and mechanisms involved in the reaction of ninhydrin with α-amino acid.

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