— n6 — 



J. Houben 1 ) reports on syntheses of aromatic carboxylic acids 

 by means of Grignard's reaction. It is a well known fact that, 

 according to V. Grignard, carboxylic acids can readily be obtained 

 by allowing carbon dioxide to act on the organomagnesium salts, and 

 decomposing the intermediate products formed with dilute sulphuric 

 acid: R-MgX-f C0 2 = R.CO.OMgX; R. COOMgX-J-H 2 = R 

 • COOH-f-HO.MgX. 



Already in 1902, J. Houben and L. Kesselkaul 2 ) have employed 

 this method for the production of aromatic and hydroaromatic carboxylic 

 acids. The work under review gives the composition of a few syntheses 

 in the series of aromatic and hydroaromatic carboxylic acids. First 

 of all Houben describes the action of magnesium and p-dibrom- 

 benzene in ethereal solution in the presence of a small quantity of 

 methyl iodide. By allowing carbon dioxide to act on the reaction 

 mass, he obtained terephthalic acid in addition to p-brombenzoic acid 

 and p-dibrom-acetophenone. 



Hydropinene carboxylic acid C 10 H 17 • C O O H, he obtained 

 in a yield of about 4O°/ , by pouring on 14 gm. magnesium in about 

 100 cc. absolute ether, a concentrated ethereal solution of 100 gm. 

 solid pinene hydrochloride C 10 H 17 CI, to which a small quantity methyl 

 iodide has been added. After several days, dry carbon dioxide is 

 introduced into the reaction mass. Next, the mass is decomposed 

 with ice and dilute mineral acid, and from the ethereal layer the acid 

 is isolated with soda solution. Hydropinene carboxylic acid boils at 

 atmospheric pressure at 268 °, at 13 mm. pressure at 153 °; melting 

 point 72 to 74 . It is a monobasic acid of the formula C 11 H 18 2 . 



The corresponding anhydride (hydropinene carboxylic acid 

 anhydride C 22 H 34 3 ) is formed fairly quantitatively when the acid 

 is boiled for half an hour with ten times the weight of acetyl chloride. 

 It crystallises from alcohol in silky brilliant feathers of the melting 

 point 211 to 212 . 



Hydrodicamphene. C 10 H 17 • C 10 H 17 , is formed by the action 

 of magnesium on pinene hydrochloride in ethereal solution, according 

 to Wurtz's synthesis, in a yield of 19 to 2 2°/ , when 2 molecules 

 pinene hydrochloride act on 1 molecule magnesium with formation of 

 magnesium chloride and hydrodicamphene. It crystallises from alcohol 

 in feathery crystals of the melting point 74 to 75 and boiling point 

 322 to 3 2 3 . It is scarcely attacked by concentrated sulphuric acid 

 and by chromic acid. At 12 mm. pressure it distils at 180 to 190 

 as a water-white liquid, and appears to be identical with the hydro- 

 carbon C 20 H 34 , produced by A. Etard and G. Meker 3 ), and also by 



x ) Berl. Berichte 38 (1905), 3796. 



2 ) Berl. Berichte 35 (1902), 2519 and 3695. 



s ) Compt. rend. 126 1898), 525. 



