PYRIMIDIN GROUP. 417 



Eoeder). It is difficultly soluble in cold, easily so in boiling water, 

 less easily in alcohol than in ether. Although it is neither acid 

 nor basic in character a potassium thymin compound can be obtained 

 (Steudel), with mercuric nitrate it yields a voluminous precipitate. 

 Mercuric chlorid gives no precipitate but does form one if the 

 liquid containing the mercury salt is rendered slightly alkaline with 

 sodium hydrate. In like manner silver nitrate does not yield a pre- 

 cipitate but the subsequent addition ammonium or barium hydrate 

 produces a gelatinous precipitate which redissolves in excess of the 

 alkali. 



Thymin decolors bromin water and eventually forms a bromin 

 derivative. According to Jones (1900) this change takes place 

 according to the equation : 



C^HgNjOj + 2Br + Hp = C^H^N^OjEr + HBr. 



On heating with phosphorus oxychlorid Steudel and Kossel (1900), 

 obtained a dichlorthymin which was different from that obtained from 

 the isomer methyl uracil. By heating potassium thymin with methyl 

 iodid Steudel obtained a dimethyl thymin which also differed from 

 the isomeric trimethyl uracil of Behrend. 



Although at the time of the discovery of thymin Kossel suggested 

 that it possibly might be a pyrimidin body, yet positive proof of this 

 and the demonstration of its constitution was not supplied until re- 

 cently. The pyrimidin character was demonstrated by Steudel (1901), 

 who succeeded in obtaining a nitro-thymin and this on reduction with 

 tin and hydrochloric acid gave a body which with chlorin water and 

 ammonia yielded an intense murexid reaction, thus indicating the 

 presence of the alloxan group. This was further corroborated by the 

 oxidation of thymin with barium permanganate, urea being obtained. 

 In view of these reactions thymin is a pyrimidin body isomeric with 

 methyl uracil. The di-substitution products indicate that thymin pos- 

 sesses the following structural formula : 



<I— CH HN— OH N=CH 



Thymiw. Ubaoil. Fyrikidih. 



CjHjNA- C,H.NA- C.H^N,. 



The position of the carbon and nitrogen is indicated by numbers 

 in the same way as in the case of purin (p. 338). Thymin is there- 

 fore 5-methyl 2-6-dioxypyrimidin. Methyl uracil, the isomer syn- 

 thesized by Behrend and Eoosen, has the methyl group in position 

 4 ( = 6). It is prepared by the action of urea on acetacetic ether. 

 Gabriel and Colman * changed methyl uracil into 4 ( = 6) methyl 

 pyrimidin and eventually into pyrimidin. From the 4.5.6-metLyl 



>£encA(e. 32, 1537(1899). 

 27 



