Chemical structures ninhydrin

Ninhydrin (1,2,3-triketohydrindene monohydrate). Widely available chemical, light-sensitive. Ninhydrin reacts with free amines (2 1 molar ratio), giving a purple product (Ruhemann s purple resonance structure). Used for a qualitative test to determine the presence of aliphatic amines on the agarose beads as a 0.2% w/v solution in ethanol (see Note 4). Hazards Harmful if swallowed skin, eye, and respiratory irritant. Toxicity data LD50 78 mg/kg intraperitoneal, mouse. Should be handled in a fume hood with safety glasses and gloves. 

Know the names, structures, and classification of all amino acids and their side chains present in proteins, and be familiar with their physical and chemical properties, such as conformation, absorption of ultraviolet light, and reactions with ninhydrin. 

The structure elucidation of 34 was based, in principle, on two facts color reactions and hydrolysis. Compound 34 does not react with ninhydrin (therefore, no primary amino group is present) but it does react with l-fluoro-2,4-dinitrobenzene. By exact determination of the absorption ratio E35O/E390 after the reaction with the latter reagent, Tait concluded that 34 contains a secondary amino group (50). Hydrolysis (6 N HC1, 110°C, 24 hr) of the so-called compound II afforded 2,3-dihydroxybenzoic acid and spermidine (50). The presence of two 2,3-dihydroxybenzoyl residues in 34 was demonstrated by its enzymatic (50) and chemical synthesis (51-54). 

Another structural revision is concerned with the repqrted " formation of the thiazine system (127) in the reaction of ninhydrin with cysteine. The chemical and spectroscopic properties of the condensation product are in... 

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