112 REPORT — 1875. 



Report of the Committee, consisting of Dr. H. E. Armstrong and 



Dr. T. E. Thorpe, appointed for the jJurpose of investigating Iso- 



■ meric Cresols and their Derivatives. Drawn up by Dr. Armstrong. 



Since the last Meeting of the Association a number of derivatives of para- 

 cresol have been examined, and some attention has been given to the isomeric 

 cresols ; but the investigation has meanwhile assumed a much wider aspect 

 than originally intended, having become a study of the " law of substitution " 

 in the phenol series, for reasons which may be briefly stated as follows. 



The examination of the derivatives of phenol, C^ Hj OH, carried on during 

 the past four years by various chemists, has shown conclusively that substi- 

 tution takes place in that compound in a very definite and simple manner. 

 Kekule's theory, it is well known, admits of the existence of three isomeric 

 mono-derivatives of phenol ; and it has been found that the action of all 

 reagents which lead to the production of substitution derivatives always gives 

 rise to the simultaneous production of two of the three, the so-called ortho- 

 and prtrrt-derivative. The third isomeric (so-called meta-) mono-derivative 

 is seldom formed in any quantity, if at all ; thus there is no evidence to show 

 that it is produced in the ease of the action of nitric or sulphuric acid, and it 

 is formed only in very small quantity by the action of chlorine and bromine ; 

 the action of iodine, however, appears to give rise to a somewhat larger amount 

 of the meta-derivative. The further action of reagents on the ortho- and 

 para-mono-derivatives leads ultimately to the production of ^/'^-derivatives, 

 and under ordinarj' conditions iliere is no tendency to the formation of liigher 

 substituted derivatives. In all the di- and tri-derivatives thus directly formed 

 from phenol, it is found that the ortho- and para-positions alone are occupied ; 

 so that employing the usual hexagonal symbol to represent phenol, what, 

 in the absence of a better expression, may be termed the direction in which 

 substitution is effected in phenol may be graphically represented, somewhat 

 in the manner suggested by Huebner, by lines drawn within the hexagon, 

 thus : — 



OH 



(Oi-tho-position) EC ^^•'*" ""-v!^ 



(Meta-position) H!C. 



.. CH (Ortho-position) 



-T* 



^ CH (Meta-position) 



C 



II 



(Para-position) 



It is evidently a pi'oblem of considerable importance to determine whether 

 this very simple " law of substitution " obtains in the case of the homologues 

 of phenol ; and our experiments have all been instituted in the hope of con- 

 tributing to its speedy solution. The behaviour of paracresol and of thymol 

 has, to a certain extent, already been studied, and experiments with the 

 isomeric cresols, ethylxDhenol, xylenol, and carvacrol are in progress. 



Paracresol derivatives. — Paracresol, C^ H^ (CH,) OH, being formed from 

 phenol by the displacement of the atom of hydrogen in the p«;-«-position by 

 methyl, it should yield c?i-derivatives only if the " law " above discussed is 

 capable of application, and would accordingly be represented by the symbol : — 



