ON THE STUDY OF HYDRO-AROMATIC SUBSTANCES 157 
On the other hand, with acetic anhydride in presence of only traces 
of alkali C-acetyl derivatives are formed (2). In contradistinction to the 
O-acetyl derivatives, these bodies have marked acid properties, and give 
an intense ferric chloride reaction. On boiling with mineral acids they 
are decomposed into acetic acid and substituted dihydroresorcin, and 
oxidation with sodium hypobromite converts them into substituted 
glutaric acids. 
O-acetyl derivatives are converted into C-acetyl derivatives by heating 
with acetic anhydride and a trace of alkali. 
The possibility of using condensing agents other than alkali has been 
experimented on, and it is shown that dimethylaniline and quinoline 
produce O-acetylation ; pyridine and tripropylamine produce C-acetyla- 
tion, and concentrated sulphuric acid principally C-acetylation, but to a 
small extent O-acetylation. 
Acids.—The fractions obtained in the distillation of petroleum may 
be converted into the corresponding carboxylic acids! by chlorinating, 
adding magnesium and a catalytic agent, passing a current of carbon 
dioxide, and decomposing the complex magnesium compound thus 
obtained. The method is more particularly applicable for the preparation 
of fatty acids, but the fraction boiling at 80° to 82° yields pure hexa- 
hydrobenzenecarboxylic acid, and the fraction 71° to 79° this same acid 
mixed with methyleyclopentanecarboxylic acid. 
When acetonedipropionic acid ? CO(CH,.CH,.CH,.COOH),, obtained 
by the hydrolysis of ethyl ketoheptanetetracarboxylate, is heated, water 
is eliminated and dihydroresorcinpropionic acid results. It possesses all 
VAIS 
CH CH.CH, CH,.COOH 
4 2 2 
\cu,.coZ 
the characteristics of the dihydroresorcin derivatives.* 
Following von Baeyer’s directions‘ for the reduction of phthalic acid, 
Abati and Bernardinis® have isolated three new substances, namely, 
cis-A?-tetrahydrophthalic anhydride, 4'**-dihydrophthalic anhydride, and 
a substance M.P. 174°, which is most probably a dihydrophthalic 
acid. 
Von Baeyer has shown ® that the reduction of isophthalic acid takes 
place with much greater difficulty than in the case of phthalic or tere- 
phthalic acids. He obtained an acid melting at 199° which agreed on 
analysis with a tetrahydroisophthalic acid. In 1891 Perkin’ synthesised 
the cis- and trans-modifications of hexahydroisophthalic acid, and shortly 
afterwards Baeyer and Villiger® obtained these same cis- and trans-acids 
by the direct reduction of isophthalic acid. 
Perkin and Pickles 9 have now obtained all four possible tetrahydro- 
isophthalic acids also by direct reduction of isophthalic acid, and for 
reasons given in the original paper these authors conclude that the con- 
! Zelinsky, D. R. P., 151880. 
2 Yon Pechmann and Sidgwick, Ber., 1904, 37, 3816. : 
3 Compare Merling, Annalen, 1894, 278, 20, and Vorlaender, ibid., 1897, 294, 270. 
4 Annalen, 1890, 258, 199. 5 Cent. Blatt., 1905 (1), 1318. 
® Ber., 1886, 19, 1806. 7 J. C.8., 59, 808, 
5 Annalen, 1893, 276, 255. 
® 7. E. 8, 1905, 87, 293, 
