544 SCIENCE PROGRESS 



substituted did not react, or formed additive compounds 

 containing a mercurichloride group in position 3. 



CH— CH CH— CH CH-<:H 



li II -> II II and II II 



CH CH CH CHgCl ClHgC CHgCl 



\ / \ / * \ / 



s s s 



CH CH CH CH 



II II -> II II 



CCfiHg CH CQHg CHgCl 



s s 



CH CH CH CH . HgCI 



II II -> II I 



CMe CMe CMe CMe.OH 



/ V 



He pointed out, however, that certain irregularities occurred. 

 Further work has emphasised the fact that the above con- 

 clusions do not invariably hold. For example, 3:4 diphenyl- 

 thiophen does not react with mercuric chloride in the cold, and 

 behaves abnormally when heated with this compound ; again, 

 2:4-dimethylthiophen [i] and 2:5-diphenylthiophen [ii] both 

 behave in an unusual way. 



CMe CH HO. CMe CH CMe CH 



II II -^ I II -^ II II 



CH CMe HgCl2.ClHgCH CMe ClHgC CMe 



S S S 



[i] 



CH CH CH CHgCl 



II II -> II II 



CPh CPh CPh CPh 



\ / "^ / 



s s 



[ii] 



In addition, the conversion of the mercurichlorides into the 

 mercury dithienyls by the action of sodium iodide is not, as 

 was formerly thought, a reaction characteristic of mercuri- 

 chlorides of thiophen in which the mercurichloro group is 



i 



