200 CHEMISTRY 



RN=C ; these are in dynamic equilibrium with the absolutely 



inert molecules RN = C or better RN=C]. That this percentage 

 varies with the nature and mass of R is shown by the fact that 

 various alkylated and arylated isocyanides manifest different degrees 

 of chemical activity. Carbon monoxide possesses relatively a smaller 



number of such active particles, O =C , and consequently is a com- 



paratively inert substance, since the speed of addition reactions 

 shown by unsaturated compounds must naturally be directly in pro- 

 portion to the per cent of active molecules present. A similar concep- 

 tion obviously explains the relative differences in reactivity shown 

 by the various members of the olefine and acetylene series. Marsh 

 gas, a saturated system, reacts with other substances because it is par- 



tially dissociated as follows, CH, ? CH 3 - + H - and ^. CH 2 + 2H - . 



From this point of view chemical action depends entirely upon dis- 

 sociation processes. The reactions often proceed with very great 

 slowness because the percentage of dissociation is extremely low, 

 possibly one tenth to one thousandth of one per cent, or even less. 



Turning now to a consideration of the reactions of alkylisocyan- 

 ides; the substances which are absorbed by the unsaturated carbon 

 atom present in the isonitriles are the following. 



(1) Halogens [(chlorine, bromine, iodine) ; speed of reaction in the 

 order named]. 



X X 



\ \ 



X X 



The reactions, especially those with chlorine and bromine, take place 

 with great evolution of heat at 20. 



(2) Acidchlorides, such as RCO-C1, C1-OC 2 H 5 , C1-CO-C1, 

 Cl-CN, Cl-COOR, to form the addition products: 



Cl Cl 



/ I I 



RN=C/ RN = C-CO-C:NR, etc. 



COR, 



A hyphen denotes the point where the compounds are partially dis- 

 sociated and consequently absorbed. These reactions, especially those 

 with phosgene and ethylhypochlorite, take place with great violence 

 at -20. 



(3) Oxygen and sulphur, to form isocyanates and mustard oils, 

 RN=C=O and RN=C=S. Methylisocyanide unites directly at 

 its boiling-point, 58, with the oxygen of the air. The dry oxides 



