INTRAMOLECULAR DISPLACEMENT 89 



It however appears to be allyl mustard oil, SCN(C 3 H 5 ), 

 instead of the thiocyanate, NCS(C 3 H 5 ). The explanation 

 was given that this body is the result of a secondary 

 reaction due to the somewhat high temperature (100) 

 employed. In the cold the allyl thiocyanate expected is 

 actually formed, but it has the property of suffering an 

 inversion on heating, i. e. being converted into the isomeric 

 mustard oil. Two facts are thus simultaneously established: 

 first, that an inversion of atoms within the molecule may 

 stand in the way of determining constitutions by the 

 method we are discussing; second, that to exclude such 

 secondary changes, high temperatures should be avoided in 

 determining constitution. 



It has not so far always been found possible to analyse 

 these modified reactions, and distinguish with certainty the 

 primary reaction to be arrived at ; e. g. pinacone, which has 

 the constitutional formula 



(CH 3 ) 2 COHCOH(CH 3 ) 2 , 

 is converted by withdrawal of water into pinacolin 



C 6 H 14 2 -H 2 = C C H 12 0, 

 which accordingly was regarded by Friedel l as 

 (CH 3 ) 2 C-C(CH 3 ) 2 



V 



o 



But as Butlerow obtained the same body from trimethyl- 

 acetyl chloride, (CH 3 ) 3 CO Cl, and zinc methyl, Zn(CH 3 ) 2 , 



the formula 



(CH 3 ) 3 CCOCH 3 



was equally probable, according to the equation 



2(CH 3 )CCOCl-fZn(CH 3 )=:ZnCl 2 + 2(CH 3 )CCOCH 3 . 



In one of the two reactions an extra methyl group must 

 have been detached and displaced, and so far it is an open 



1 See among others Pomeranz, Wien. AkacL Ber. 106. 579 (1897). 



