Betaïne

Betaïne (Oxyneurine, Lycine), C5H13NO3, a substance discovered in the sugar beet (Beta vulgaris) in 1869 by C. Scheibler (Ber., 1869, 2, p. 292). It is also found in cotton seed, in the vetch and in wheat sprouts (E. Schulz and S. Frankfurt, Ber., 1893, 26, p. 2151). It may be synthetically prepared by oxidizing choline with chromic acid (O. Liebreich, Ber., 1869, 2, 13), (CH3)3N(OH)·CH2·CH2OH -> C5H13NO3 \+ H2O; by heating trimethylamine with monochloracetic acid (Liebreich), (CH3)3N + CH2Cl·COOH = (CH3)3N(Cl)·CH2·COOH (betaïne hydrochloride); and by heating amino-acetic acid (glycocoll) with methyl iodide in the presence of an alkali (P. Griess, Ber., 1875, 8, p. 1406). It crystallizes from alcohol in large deliquescent crystals; and is readily soluble in water, but insoluble in ether. It is a weak base. As is shown by the various syntheses of the base, it is the methyl hydroxide of dimethyl glycocoll. This free base readily loses water on heating and gives an internal anhydride of constitution  which is the type of the so-called “betaïnes.” These organic betaïnes are internal anhydrides of carboxylic acids, which contain an ammonium hydroxide group in the α-position. A. Hantzsch (Ber., 1886, 19, p. 31) prepared the betaïnes of nicotinic, picolinic and collidine carboxylic acids from the potassium salts of the acids, by treatment with methyl iodide, followed by moist silver oxide. The reaction may be shown as follows:—

The methyl betaïne of nicotinic acid is identical with the alkaloid trigonelline, which was discovered in 1885 by E. Jahns in the seeds of Trigonella faenum-graecum (Ber., 1885, 18, p. 2518). It has also been obtained from nicotine by A. Pictet by oxidizing the methyl hydroxide of nicotine with potassium permanganate (Ber., 1897, 30, p. 2117).

Substances closely related to betaïne are choline, neurine and muscarine. Choline (bilineurine, sincaline), (Gr. χολή, bile), C5H15NO2 or HO·CH2·CH2·N(CH3)3·OH, first isolated by A. Strecker in 1862 (Ann. 123, p. 353; 148, p. 76), is found in the bile, in brain substance, and in yolk of egg in the form of lecithin, a complex ester of glycerin with phosphoric acid and the fatty acids. It is also found in combination with sinapic acid in sinapin, the glucoside obtained from white mustard, and can be obtained from this glucoside by hydrolysis with baryta water,

C16H23NO5 \+ 2H2O | = | C5H15NO2 | + | C11H12O5.  
---|---|---|---|---  
Sinapin. |   | Choline. |   | Sinapic acid.  
  
It can be synthetically prepared by the action of trimethylamine on an aqueous solution of ethylene oxide (A. Wurtz, Ann. Suppl., 1868, 6, p. 201). It forms deliquescent crystals of strongly alkaline reaction, and absorbs carbon dioxide from the air. It is not poisonous. By continued boiling of its aqueous solution, it is resolved into glycol and trimethylamine.

Neurine, trimethyl vinyl ammonium hydroxide (Gr. νεῦρον, nerve), CH2 : CH·N(CH3)3·OH, is a product of the putrefaction of albumen. It may be prepared by the action of moist silver oxide on ethylene dibromide and trimethylamine,

CH2Br·CH2Br -> CH2Br·CH2N(CH3)3Br -> CH2 : CH·N(CH3)3·OH.

It is a crystalline solid, very soluble in water, and is strongly basic and very poisonous. Muscarine, C5H15NO3, is an exceedingly poisonous substance found in many fungi. It may be obtained synthetically by oxidizing choline with dilute nitric acid (O. Schmiedeberg, Jahresb., 1876, p. 804). The exact constitution has not yet been definitely determined.

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