— 189 — 



is formed in the shape of fine needles, m. p. 93° On the other hand, 

 an attempt to obtain from "dichl >ro-piperonal" the corresponding glycol 

 diacetate CO»0 2 -CgHg-CH^OCOCHg^ by means of acetate of 

 silver, proved the chlorine atoms to be linked comparatively firmly. 

 The expected body, which crystallised out in warts (m. p. 84,5 to 85 ) 

 from ligroin-benzene could only be readily obtained by boiling dichloro- 

 piperonal with acetate of silver and aceiic anhydride for several hours. 

 The reduction of "dichloro-piperonal" by zinc dust and glacial acetic 

 acid, which proves its constitution, and which had been carried out 

 previously, yields almost 90 per cent, of the theoretical quantity of 

 homo-pyrocatechol carbonate when the following method is applied: 

 instead of dissolving the concentrated acid solution in water and neu- 

 tralising it with soda when the process of reduction is completed, the 

 residue is dissolved in chloroform, the glacial acetic acid still remaining 

 is repeatedly extracted with water until the acid reaction has ceased; 

 and after drying the solvent is evaporated and the residue distilled 

 in vacuo. Under certain conditions, when completely anhydrous glacial 

 acetic acid is used and the operation is conducted in the cold way, 

 it is possible, by adding known quantities of zinc dust, to carry the 

 reduction only up to the point where the carbonate of the 3, 4-di- 

 hydroxy-benzylchloride CO • 2 • C 6 H 3 • CH 2 C1 (lustrous needles, 

 m. p. 53,5 to 54 , from ligroin) is formed. Boiled with acetate of 

 silver and acetic anhydride, this body yielded the corresponding car- 

 bonate of the 3,4-di-hydroxy-benzylalcohol, m. p. 59,5°. With pyridin 

 and the required volume of water, the theoretical quantity of carbonic 

 acid was split off from the carbonate, but with simultaneous formation 

 of a pyridinium-compound, probably of the following formula: (HO) 2 

 • C 6 H 3 . CH 2 N(C1): C 5 H 5 melting between 170 and 171 . 



Ketones. 



Methyl-heptenone. It has been stated by Verley 1 ) that when 

 methyl-heptenone is heated with sulphuric acid as a dehydrating agent, 

 it yields 1,3 -dimethyl cyclohexadiene. 



In order to prepare this compound, W. Crossiey and N. Renouf 2 ) 

 heated methyl-heptenone with sulphuric acid, but in doing so they 

 obtained a hydrocarbon which boiled somewhat inconstantly at from 

 130 at 1 3 2° and of which the analytical constants pointed to a mixture 

 of dimethyl -cyclohexadiene and dimethyl -cyclohexane. The same 

 result was observed' when chloride of zinc and phosphorus pentoxide 

 were used. Wallach had informed the authors that the hydrocarbon 

 which is formed when water is eliminated from methyl-heptenone is 



*) Bull. Soc. Chim. III. Yi (1897), 180; Report April 1897, 53. 

 2 ) Journ. chem. Soc. 95 (1909), 930. 



