— 150 — 



As a matter of fact, there was formed, by splitting off the 

 carbonyl-group situated at the tertiary carbon atom, as might be 

 expected, the compound II, the lactone of an as yet unknown hydroxy- 

 cinenic acid, which was proved by the conversion of the latter in 

 1, 3-dimethylbenzoic acid-4 1 ); this speaks against the formation of 

 compound III. 



With regard to the position of the bromine atoms in the sub- 

 stitution products, Rupe and Lotz do not express any definite 

 opinion. 



The hydroxycinenic acid lactone just described is formed by treating 2 ) 

 cineolic acid, or better still its anhydride, with concentrated sul- 

 phuric acid in the cold, which reaction is also accompanied by 

 loss of carbon oxide. The loss takes place, as above, at the tertiary 

 carbon atom. If the lactone melting at 50 to 51 is heated with 

 concentrated sulphuric acid, or if cineolic acid or its anhydride are 

 heated directly with oil of vitriol, the above-mentioned 1, 3-dimethyl- 

 benzoic acid-4 (m. p. 125 to 12 6°) is obtained: — 



CK CH, 



O C. 



CH 3 .C( >CH 



I \ch 2 .ch/ 1 



O CO 



lactone of hydroxycinenic acid 



CEL-C 



CH 8 

 I 



OH CK.C, 



V 



I ^CH 2 CH/ I 



O CO 



intermediate product 

 CH, 



H 2 + H 2 + CH 3 .C 



// 



CH- 



^ 



C-COOH 



CH = CH/ 



dimethylbenzoic acid 



It will be seen from the formulae that the sulphuric acid has a 

 condensing as well as an oxidising action. But from an attempt 

 to arrive at dihydrodimethylbenzoic acid, in a manner analogous to 

 the formation of dihydro-m-xylene from cineolic acid according to Wal- 

 lach and Gildemeister 3 ), by melting the above-described lactone with 

 zinc chloride, it would appear that the intermediary formation of the acid 

 is not impossible. Dihydro-m-xylene boiled at 132 to 134,5° (according 

 to Wallach and Gildemeister at 132 to 134°); n D20° 1,46867; the 

 dinitroxylene produced from it melted at 90 to 91°. 



*) Comp. hereafter the action of sulphuric acid on cineolic acid. 



2 ) Berl. Berichte 39 (1906), 4083. 



3 ) Liebig's Annalen 246 (1888), 268. 



