352 
Mr Hill , The Orientation of a 
iodide obtained by the action of methyl iodide on dimethyl 
p-brom aniline : the melting-point of 200° G, higher than that of 
any of the other bromphenyl ammonium iodides, the crystalline 
form and the extremely small solubility in alcohol, all showed the 
two compounds to be identical. 
The mixture of ?i-propyl iodide and dimethyl p-bromaniline 
gave a small quantity of quaternary iodide at the ordinary tem- 
perature, which on recrystallisation from alcohol had a melting- 
point of 170° C. It appeared to be identical with the compound 
formed bj' the action of methyl iodide on methyl propyl brom- 
aniline, which also melts at 170° C. Consequently the latter has 
its bromine atom in the para position. 
The mixture of isopropyl iodide and dimethyl p-bromaniline 
gave a small quantity of solid which has not been identified ; and 
in the case of isobutyl and isoamyl iodides there was practically 
no action. 
If heated to 100° C., the mixtures of dimethyl p-bromaniline 
and alkyl iodides deposited solid fairly rapidly. It was shown to 
consist largely of p-bromphenyl trimethyl ammonium iodide in 
every case. 
This formation of the trimethyl compound appears to be due 
to the dissociation of ammonium salt into alkyl iodide and tertiary 
amine. The mechanism is probably somewhat thus : 
C 6 H 4 Br . (CH 3 ) 2 N + C 2 H 5 I ^ C 6 H 4 Br . (CH 3 ) 2 N . C 2 H 5 . 1 
C G H 4 Br . (CH 3 ) 2 N . C 2 H 5 . 1 Z C 6 H 4 Br . CH 3 . C 2 H 5 . N + CH 3 I 
C 6 H 4 Br.(CH 3 ) 2 N + CH 3 I X C 6 H 4 Br . (CB*) S . NI 
The trimethyl compound, being much more sparingly soluble 
than any of the other quaternary iodides which might be formed, 
will separate out and be removed from the sphere of action. This 
would account for its being the chief product of the reaction. 
So far the constitutions of only two members of the series had 
been proved — the ethyl and the n-propyl compounds. Some other 
method of orientation had, consequently, to be looked for. A 
reaction was eventually discovered which enabled the whole series 
to be orientated. 
It was found that if the quaternary iodides, obtained by the 
action of methyl iodide on the bromanilines and having the 
general formula C G H 4 Br.(CH 3 ) 2 (R) NI, were heated with excess of 
methyl iodide in sealed tubes at 100° G, p-bromphenyl trimethyl 
ammonium iodide was produced. In some cases the action was 
almost complete after two hours heating. But in the case of the 
isoamyl compound the action was very slow, and it was at first 
thought that no trimethyl compound had been produced ; however. 
