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Chapter 24: Q17P. (page 1273)

Use resonance forms to show delocalization of the negative charge in Ruhemann’s purple anion.

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Formation of Ruhemann’s purple anion

Resonance form of Ruhemann’s purple anion

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01

Formation of Ruhemann’s purple anion

When ninhydrin reacts with an amino acid, the product formed is a deep violet resonance-stabilized anion known as Ruhemann’s purple. The reaction of an amino acid with ninhydrin is shown below:

Formation of Ruhemann’s purple anion

02

Resonance form of Ruhemann’s purple anion

The resonance form of Ruhemann’s purple anion is as shown below:

Resonance form of Ruhemann’s purple anion

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Draw the electrophoretic separation of Trp, Cys, and His at pH 6.0.

The herbicide glyphosate(Roundup) kills plants by inhibiting an enzyme needed for synthesis of phenylalanine. Deprived of phenylalanine, the plant cannot make the proteins it needs, and it gradually weakens and dies. Although a small amount of glyphosate is deadly to a plant, its human toxicity is quite low. Suggest why this powerful herbicide has little effect on humans.

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