T h e first successful p r c p a r a t i o~~ of w,wl-clibromidcs from the electrolyses of a series of w-bromoc-arbosylic acids, Br(CIH?),,COOI-I (12 = 5 to 17 = 11), is reportecl. U~~d e r r o~~d i t i o~~s of fairly lo\\-temperature and c u r r c~~t density, yields from 5-L to Sl';& of these clibromitles \yere obtained.T h e electrolysis of 11-bromouncleca~~oic aricl is discussed a s a n e s a~n p l e of ho\v a s~n a l l change in experimental conclitions can produce a collsiclerable change in the protlucts of reaction. A t 50°, t h e product was mainly 1,20-dibronloeicosane, \\rhercas a t 65' the protlucts \yere mainly the esters methyl 11-bromo~~ndecanoate ant1 methyl 11-metl~osyundeca~ioi~tc. I t has been reported (1) that w-bromocarbosylic acids with cllain l e~~g t h s of 10 cni-bolls or less do not electrolyze normally to yield w,wl-dibromicles, while those with gi-eater chain lengths behave as expected (the acicls used were of formula Br(C1-I?),,COOI-I, wllere n = I-,?, 7, 9, 10, 1.7). No products were isolated and ideiltifiecl in these non-couplillg reactions. Later, a successful mised coupling reaction involving S,T,-dimethyl-6-bl-onlol~exanoic acicl (I) was run ( 2 ) , but 110 experimental details regarding conditions, yields, etc. were gi\.en. Also, 11-bromoundecanoic acid, which has been electrolyzed normally on nlore than one occasion (1, 3), has been 1;nown (4) to split out brotlii~~e ~~n d e r a high temperature of reaction, to yield a neutral product not identifiecl further.I11 view of these uilespected and sometimes conflicting results, a thorough investigation of the electrolyses of w-bromocarbosylic acicls seemecl necessary. This investigatioll has procluced the first successf~~l anodic couplings of G-broinohexanoic acid, 7-bromoheptanoic acicl, 5-bron~ooctanoic acid, 9-bromononanoic acicl, 10-bromodecanoic acid, ancl 12-bron~odocleca~~oic acicl, giving the corresponcling w,wl-clibromides in yields of 54-71%. These clibromicles, while known compounds, have not been made previously b\-the Icolbe reaction.The \\-ork reported is part of a study being carried out 011 electrolyses of w-bromocarbosylic acids \\rliicli may or may not electrolyze normally, i.e. produce w,wl-dibromides in reasonable J ield. The results show that w-bromocarboxylic acids of chain lengths from Ci to 12 \\rill electrol5 ze to give the expected symmetrical coupling products. T h e best esperimental conditions seem to be a Iow temperature of reaction (at least below 50" ancl often below 40") and not too high a current density. Norinally such factors as concentration of acid, current density, temperature of reaction, etc. are not nearly so critical for electrolyses in absolute illethailol as they are for electrolyses in aqueous media (5, G). I-Io~vever, for the w-bromocarboxylic acids, it appears that these factors may be much more critical than for various unhalogenated acids and half-esters. Certainly, temperature of reaction seems to be quite critical if a good yield of the dibromide is desired. So, while the results in t...
