Triketohydrindene hydrate

Ninhydrin (also named 1 2 3-triketoindane or 1 2 3-triketohydrindene hydrate) is prepared most simply from the inexpensive phthahc anhydride (I). The latter is condensed with acetic anhydride In the presence of potassium acetate to give phthalylacetlc acid (II) reaction of the latter with sodium methoxide in methanol yields 1 3-indanedionecarboxyhc acid, which is decomposed upon warming with dilute hydrochloric or sulphuric acid to indane-1 3-dione (or 1 3-diketohydrindene) (HI). Selenium dioxide oxidation of (III) afibrds indane-1 2 3-trione hydrate (ninhydrin) (IV). 

Ninhydrin (1,2,3-triketohydrindene hydrate) [485-47-2] M 178.1, m 241-243 (dec), pK 8.82. Crystd from hot water (charcoal). Dried under vacuum and stored in a sealed brown container. 

Detection powders and fingerprint development kits commonly contain cream- or yellow-colored ninhydrin crystals or a solution of dissolved ninhydrin. Ninhydrin (also known as 1,2,3-indantrione, monohydrate 2,2-dihydroxy-1,3-indandione triketohydrindene, monohydrate and triketohydrinden hydrate) has the structure presented in Fig. 13.3.1. Ninhydrin will react with a free a-amino group, -NH2. This group is contained in all amino acids, and analysis with ninhydrin is often performed to verify the presence of amino acids. When a-amino acids (i.e., amino acids with the structure NH2-CHR-COOH) react with ninhydrin, a characteris-... 

Ninhydrin (triketohydrindene hydrate) reacts with an amino acid when heated under acidic conditions (pH 3-4) to produce ammonia, carbon dioxide and a blue-purple complex. This reaction forms the basis of many widely used methods (Figure 10.11). One mole of carbon dioxide is liberated from each mole of amino acid, exceptions being the dicarboxylic amino acids, which produce two moles of carbon dioxide, and the a-imino acids, proline and hydroxyproline, which do not produce carbon dioxide. Although this formed the basis of a gasometric technique, colorimetric methods are now the most common. 

Ninhydrin Reaction. A neutral solution of an amino acid will react with ninhydrin (triketohydrindene hydrate) by heating to cause oxidative decarboxylation. The central carbonyl of the tnketone is reduced to an alcohol. This alcohol further reacts with ammonia formed from the amino add and causes a red-purplish color. Since the reaction is quantitative, measurement of the optical density of the color produced is an indication of amino add concentration. Imino acids, such as hydroxyproline and proline, develop a yellow color in the same type of reaction. 

Triketohydrindene Hydrate TS (Ninhydrin TS) Dissolve 200 mg of triketohydrindene hydrate (C9H4O3 H2O) in water to make 100 mL. Prepare this solution fresh. 

Identification Heat 5 mL of a 1 1000 solution with 1 mL of triketohydrindene hydrate TS (ninhydrin TS). A reddish purple color appears. 

Dithiobis (2-nitrobervzoic acid) ninhydrin (triketohydrindene hydrate)... 

Ninhydrin (triketohydrindene hydrate) Primary amine (440 nm), secondary amine (570 nm) 100 pmol 30 min postcolumn Low sensitivity and resolution Good reprodudbiUty... 

Proteins respond to the following color tests (a) biuret, pink to purple with an excess of alkali and a small amount of copper sulfate (b) ninhydrin. a blue color when boiled with ninhydrin (triketohydrindene hydrate), which is intensified by the presence of pyridine (c) Millon s test for tyrosine, a brick-F color or precipitate when boiled with mercuric nitrate in an excess of nitric acid (d) Hopkins-Cole test for tryptophan, a violet zone with a salt of glyoxylic acid and stratified over sulfuric acid and (e) xanthoproteic test, a brilliant orange zone when a solution in concentrated nitric acid is stratified under ammonia. Almost all so-called alka-loidal reagents will precipitate proteins in slightly acid solution. 

Ninhydrin (triketohydrindene hydrate) reacts with a-amino acids to produce CO2, NH3, and an aldehyde with one less carbon than the parent amino acid. In most cases, a blue or violet compound (proline and hydroxyproline give a yellow color) is formed owing to reaction of the liberated NH3 with ninhydrin, as shown in Figure 2-11. Color and CO2 production provide a basis for the quantitative determination of amino acids. 

The second method involves staining larval entry holes in pulse seeds. In the third method, ninhydrin (triketohydrindene hydrate) has been used to react with the body fluids of insects developing inside grains. A purple spot develops when ninhydrin reacts with the free amino acids (and keto acids) present in the body fluids of insects (Dennis and Decker, 1962). Ninhydrin at a 0.3% level in acetone is impregnated into filter paper. When infested grains are crushed between the folds of ninhydrin-treated paper, the body fluids from the crushed insect bodies react with ninhydrin in the paper. Purple spots develop in the paper in 20-30 minutes at room temperature (20-25 °C), the number of spots indicating the number of insects present. 

---