— 169 — 



acetobromohydrin : do© 1,249, b. p. 160 with decomposition (13 mm. 

 pressure); cyclopropanol: b. p. of the crude fraction 145 to 160 

 (15 mm. pressure), m. p. 79 ; acetate of the cyclopropanol: doo 1,123, 

 b. p. 164 to 165 (13 mm. pressure); hydratropic aldehyde: doo 1,089, 

 b. p. 253 to 255 ; oxime: m. p. 98 ; semicarbazone : m. p. 136 ; 

 hydratropic acid: m. p. 5 8°. 



2. Safrol. Cyclopropanol: d o 1,286, b. p. 170 to 178 (15 mm. 

 pressure); acetate, do© 1,255; oxime of the hydratropic aldehyde: 

 m. p. 71 ; semicarbazone: m. p. 15 8°. 



The formation of aldehydes and ketones from a -glycols is ac- 

 complished (as Tiffeneau has demonstrated in various earlier works), 

 in the first case without displacement of linkings, in the second with 

 such, according to the following formulae: — 



1. Re-arrangement without linking- displacement : 



* I 

 Ar. CHOH-CHOH. R ► Ar. CH :COH : R > Ar. CH 2 CO . R. 



2. Re-arrangement with linking- displacement : 



* /Ar. 



Ar. CHOH-CHOH. R ► Ar. COH:CH.R ► CHO-CH<( 



X CH 3 



A migration of carbon atoms consequently occurs only if the more 

 stable of the two hydroxyl radicals is situated in proximity to the aryl 

 rest. A typical example of such a re-arrangement is the formation of 

 diphenylacetic aldehyde from hydrobenzoin. 



In view of the conversion (observed by Balbiano and Paolini) 1 ) 

 of a-glycols into hydrocinnamic aldehydes (by means of ZnCl 2 ): — 



Ar. CHOH-CHOH- CH 3 ► Ar. CH 2 . CH 2 . CHO 



although these were not clearly identified, and whose oximes and 

 semicarbazones showed melting points which agreed rather with those 

 of the arylacetone derivatives (Walla ch, Hoering, Behal and 

 Tiffeneau) than with those of the derivatives of hydrocinnamic 

 aldehyde (Fourneau and Tiffeneau), — Tiffeneau and Dauf resne 2 ) 

 undertook to test the reaction mentioned above under No. 1, for its 

 general applicability. 



The glycols were obtained from the dibromides of the propenyl 

 ethers through the acetobromohydrins, which on treatment with 

 acetates of heavy metals (Ag, Pb) yielded partly bromophenyl ethers, 

 and partly glycol diacetates. The derivatives hitherto produced from 

 anethol had the following constants: acetobromohydrin: do© 1,460, 

 b. p. 180 to 185 (14 mm. pressure): bromopropenyl ether: doo 1,325, 



*) Comp. Report April 1906, 100. 

 2 ) Compt. rend. 144 (1907), 1354. 



