Nn ans > ; 
ed i nitroquinol Fone Bhsopiciol and soon fet a few pate were taken out 
a 5 weil as pyrocatechine from phenols with occupied para-position. | 
On the behaviour of hydroxyaldehydes with persulphates there have so far been 
_ but a few communications by Neubauer and Flatow?) who obtained much in the same 
way gentisine aldehyde, C;H3(OH),(CHO) from salicylaldehyde, Cs H.(OH)(CHO). When 
E extending the persulphate reaction on anisaldehyde, piperonal, and vanilline, K. Elbs — 
_and H. Lerch’) ascertained that no hydroxylation of the benzene nucleus takes place. 
_ Anisaldehyde produces a nearly quantitative yield of anisic acid, whilst with vanillin 
= and piperonal oxidation sets in in the benzene nucleus along with condensation and 
- formation of. diphenyl derivatives, vanillin being converted to dehydrodivanillin*). 
_ In the process of oxidation of vanillin the peculiar phenomenon is observed that ; 
_ the yield. ‘depends in a large measure on_the kind of the persulphate used. The sodium 
salt gives a quantitative yield of dehydrodivanillin, the potassium salt 60 to 70 per cent. 
SHO <> = CHO CHO 
| _ Hf “SH : Ae ACN : 
oS Hi, Ae aes ie so 3 fee he 
Bee 0s Sees | OH — OH 
- ; os _Vanillin. foe aoe: Dehydrodivanillin. 
> 
Band the ammonium salt 50. per cent. ae of the calculated quantity. Tiemann had used 
at the time ferric chloride for the oxidation of vanillin, a process which produced, 
_ even though in small yield, a dehydrodivanillin of great purity, whilst the preparation 
nraduced by means of persulphate becomes mixed with impurities which are very — 
_ difficult to eliminate. If, however, ferrous sulphate is used as oxygenator a pure © 
_ dehydrodivanillin is obtained also by means of persulphate. 
In the preparation of dehydrodivanillin the authors proceed as follows: — 30 g. vartilli 
are dissolved in 2 litres of water on the water-bath, and while stirring the solution first 
1 g. of ferrous sulphate and thereafter 25 g. of sodium persulphate are added; after 
_ 30 minutes the liquid is drawn off, the precipitate dissolved in dilute potash lye and 
_ precipitated with dilute hydrochloric acid. In this way 29 g. of chemically pure dehydro- 
 divanillin of the m. p. 305° are obtained. The position of the diphenyl bond in de- 
« hydrodivanillin, which had not been established so far, has. been ascertained by the 
authors by an examination of the nitroderivatives. Of course nitration offers difficulties — 
and also the nitration of the dimethylether andthe diacetyl compound requires strictest 
_ observation of definite experimental conditions. The dimethylether is nitrated to dinitro- 
dehydrodivanillin dimethylether by treatment with fuming nitric acid and concentrated 
sulphuric acid. In exactly the same way diacetyldehydrodivanillin yields dinitrodiacetyl- 
_ dehydrodivanillin (I) (m. p. 90°) which, by reduction with tin and hydrochloric acid, is 
_ converted to diacetyldimethoxydehydrodianthranil (Il). As by the formation of the di- 
anthranil derivative the ortho-position of the nitro group to the aldehyde groups is 
a proved, the position of the diphenyl bond is determined. For besides the suggested 
1) Journ. f. prakt. Chem. M1. 48 (1893),: 193. — *) Chem. Zentralbl. 1907, Il. 901. — 3) Journ. f. prakt. 
Chem. Il. 98 (1916), 1. — 4) F. Tiemann, Berl. Berichte 18 (1885), 3493. ; 
for r the analogous preparation of quinol derivatives from phenols with free para-position 
z formula for the dinitrodiacetyldehydrodivanillin only one more (Ill) would remain in 
