SYNTHESIS OF ORGANIC COMPOUNDS BY IONIZING RADIATION 



(e) Unidentifird polymers which did yield some glycine on drastic treat- 

 ment. Some products were carried down with trichloracetic acid (as 

 proteins are carried), but this behaviour is not specific for proteins. 



It is interesting to notice at this stage that it has been claimed that the 

 presence of an aromatic ring seems to be necessary for the radiation con- 

 densation of amino acids to polypeptides"-'. Phenylalanine, tryptophane and 

 tyrosine are condensed to polypeptides l:)ut glycine, alanine, leucine, valine, 

 lycine, glutamic acid and aspartic acid are not. 



SYNTHESIS OF UREA 



Loiseleur and Petit reported the synthesis of urea following the irradiation 

 of an ammoniacal and methanolic solution of ;?2-phenylenediamine and 

 dichloromethane with X-rays in the presence of air-^-'-'. They showed that 

 the formation of urea depended upon the concentration of diamine and the 

 irradiation dose falling off beyond certain values for both, and that, of the 

 diamine isomers, only m-phenylenediamine was efficacious. 



The urea present after irradiation was precipitated as the insoluble 

 dixanthylurea by the addition of 10 per cent methanolic solution of xanthy- 

 drol. The nitrogen content of this derivative was reported as 6-665 per cent 

 (theoretical 6-66 per cent). 



The proposed mechanism for this reaction was as follows, the need for 

 w-phcnylenediamine suggesting an intermediate stage: 



CI HoN HN 



HgC + CgH, > HoC CgH, + HCl 



\ / "II 



CI H,N CI NH, 



12 



NH2 



2NH3 Oxidation and 

 30 hydrolysis step 



OC + C6H4 + HCl -I- H2O 



2 



/ 

 NH2 NH2 



However, it is quite likely that the reaction actually proceeds by the initial 

 formation of an aromatic phenol leading to a relatively stable peroxide, which 

 takes part in coupling reactions with other molecules both during and after 

 irradiation. 



Our aim was to repeat this experiment using a y-ray source, to verify, if 

 possible, this reaction mechanism and then to synthesize substituted ureas. 



Irradiation Techniques 



The cell used consisted of a small round-bottomed glass tube 6 • 5 cm long and 

 3-0 cm in diameter fitted with a stopper through the centre of which passed 

 a smaller glass tube 7-0 cm long and ■ 75 cm in diameter. This small tube 



110 



