— 181 — 



trimethoxybromobenzene yields trimethoxydibromobenzene (m. p. 61°). 

 Upon heating 1, 2, 5-trimethoxy-4-bromobenzene with copper, 2,4,5,2',4',5'- 

 hexamethoxy diphenyl (m. p. 160°) results. When the bromine additive 

 product of hexamethoxy-diphenylmethane is treated with cyanide of silver 

 it yields 2,4,5,2',4 / ,5'-hexamethoxy-diphenylacetonitrile (m. p. 155°). The 

 action of hydrochloric acid upon nonamethoxy-triphenyl methane results 

 in an additive product, probably an oxonium compound. 



Ketones. 



On the reduction of methylheptenone, see p. 165. 



Menthone. An article by C. Tubandt 1 ) on the inversion of menthone 

 contains a number of interesting observations, of which we will briefly 

 mention a few which are of special interest to us 2 ). 



It has been shown that in their inverting action acids show far greater 

 differences than correspond to their strength. As an example, the action 

 of sulphosalicylic acid in the menthone-inversion is decidedly weaker 

 than that of hydrochloric acid, notwithstanding that the two acids are of 

 the same strength. It is therefore evident that in the menthone-inversion 

 there is no question of a catalysis basing on the presence of hydrogen ions. 



In studying the problem of inversion it is necessary to conduct the 

 experiments with absolutely dry solutions. The speed of inversion is ex- 

 ceedingly sensitive to the presence of water, the catalysing action of acids 

 in alcoholic solution is lowered in an extraordinary degree by the slightest 

 traces of water. This retarding action of water is only observed in the 

 case of acids; the inversion by means of bases is not affected by small 

 quantities of water. Measurement of the rate of inversion may perhaps 

 be the most stringent analytical means of proving the presence in alcohols 

 of the minutest proportions of water. 



In indifferent solvents, such as benzene, the rate of inversion is much 

 increased by the presence of small quantities of alcohol. As the alcohol- 

 content rises, the rate of inversion increases rapidly; at about 3°/o a very 

 clearly-defined maximum is reached, upon further addition of alcohol the 

 rate falls, at first rapidly, afterwards more slowly. 



In absolute and aqueous alcohol the presence of considerable pro- 

 portions of neutral salts does not affect the rapidity of the reaction in 

 the inversion by means of alcoholates. This fact is of practical importance, 

 for it makes possible the quantitative determination of the degree of salt- 

 formation between strong bases and compounds with weak acid properties, 

 such as alcohols, phenols, mercaptanes, 8jc. in alcoholic solutions. With 

 acids the conditions are very different, there the catalysing action of, 



J ) Liebigs Annalen 377 (1910), 284. 

 2 ) Comp. Report October 1905, 116. 



