35- Notes from the Chemical Laboratory of the Presidency 



CoIIegfc. Note No, S-— Reactions at Low Temperatures. 

 Part !♦ Aliphatic lodochlorides. 



^ ■ 



By BiDHU Bhushax Dutta, M.A., 



Second Assistayit^ Chemical Laboratory^ Presidency College, 



i 



Wh 



iodide at the ordinary temperature, two iaomeric cLloro-iodo- 



I I 



benzenes I [ ] and | [ ) are formed. If tlie phenyl iodide solution 



CI 

 he, however, cooled by immersing it in iced water, phenyl iodo- 



Cl 



chloride (G^J.<qy) is formed. The latter reaction is an addl- 



tive one, while the former is substitutive. The change in the 

 course of reaction with the change in temperature might be 

 explained by assuming that the phenyl iodochloride is also 

 formed in the case of tlie higher temperature, but it instantly de- 

 composes with the liberation of hydrochloric acid and formation 

 of the chloro-iodo-benzenes. 



One might expect similar reactions to occur in the case of the 

 aliphatic iodides, for in these reactions the peculiar ring structure 

 of the aromatic compounds does not particularly come into play. 

 The reaction, in this case, however, is apparently dissimilar ; for, 

 when chlorine is passed through ethyl iodide cooled to 0®, instead 

 of the expected iodochloride, we get only a liberation of iodine. 

 In the light of Nef's addition theory, the liberation of iodine might 

 be explained as due to a secondary reaction, ethyl-iodo-chloride 

 being formed in the first instance, although it is incapable of any- 

 thino- but a temporary existence at the temperature of the experi- 

 ment. It might be expected therefore that the aliphatic iodo- 

 chlorides could be isolated at comparatively low temperatures. 



The aliphatic iodide chosen for the experiment was amyl 

 iodide, because it was thought that the weight of the hydrocarbon 

 radicle might influence the stability of the iodochloride. In the 

 case of the phenyl iodochloride, which is the most stable of these 

 compounds, the weight of the phenyl group is 77, while the weight 

 of the two chlorine atoms amounts to 71, so that these two ap- 

 proximately equal weights might be expected to balance each 



other. 



) 



est approximation to the phenyl group, although the peculiar 



