Patent GB-947766-A (GB)
Title: Novel bromine-containing alkanes and processes for their production and use
IPC: C07C19/075
Filed: 1960-04-08
Abstract: The invention comprises 2-chloro-8-bromo-2, 6-dimethyloctane and 2, 8-dibromo -2, 6-di-methyloctane; their production by treating 2, 6-dimethyl -2, 7-octadiene or 2-chloro- or 2-bromo -2, 6-dimethyl-7-octene with substantially anhydrous HBr in the presence of free radicals. and the optional further steps of pyrolysis is citronellyl bromides followed by hydrolysis, esterification or etherification by replacement of the bromine atom. In specific embodiments: (a) 2,6-dimethyl -2, 7-octadiene or 2-chloro- or 2-bromo-2, 6-dimethyl -7- octene is reacted with HBr in the presence of a peroxide catalyst; (b) heating at 80 DEG -600 DEG C. produces a - and b -citronellyl bromide; (c) replacing the bromine atom by alkaline hydrolysis or by esterification with a salt of a carboxylic acid or by etherification; or (d) hydrolysing the product of step (a) with an aqueous base to obtain an 8-bromo-2-hydroxy-2, 6-dimethyloctane and subsequently the corresponding glycol.  The 2-chloro-2, 6-dimethyl-7-octene used as starting material may be obtained by reacting 2, 6-dimethyl-2, 7-octadiene with HCl in the absence of free radicals.  The free radicals required for the reaction with HBr may be produced by irradiating the gaseous mixture, by adding peroxides, or by producing peroxides in situ by blowing the olefine with air or oxygen before admission of the HBr.  If the pyrolysis step is carried out at 75 DEG -230 DEG C. in the presence of a carboxylic acid salt citronellyl esters (rich in the a -form) are obtained directly; heating in an acid medium then produces the b -citronellyl ester. In examples (1) 2, 6-dimethyl -2, 7-octadiene is hydrochlorinated to 2-chloro -2, 6-dimethyl-7-octene, which is then reacted with HBr in the presence of benzoyl peroxide to produce 2-chloro -8-bromo -2, 6-dimethyloctane; (2) 2-chloro -8-bromo -2, 6-dimethyloctane is treated with Ca(OH)2 and water to yield 2, 6-dimethyl-octane -2, 8-diol and 8-bromo -2, 6-dimethyl-octan -2-ol; (3)-(5), (8) 2-chloro -2, 6-dimethyl -7-octene, HBr and various peroxides or air give 2-chloro- 8-bromo-2, 6-dimethyloctane; (6) 2, 6-dimethyl -2, 7-octadiene, HBr and air give 2, 8-dibromo -2, 6-dimethyloctane; (7) 2-bromo-2, 6-dimethyl -7-octene, HBr and benzoyl peroxide give the dibromide; fractionation at 0.5 mm Hg gives citronellyl bromide, which with sodium acetate and acetic acid yields citronellyl acetate, saponification then giving citronellol; (9) as (3), using irradiation to produce free radicals; (10) 2-chloro -8-bromo -2, 6-dimethyloctane, acetic acid and sodium acetate give citronellyl acetate; (11) 2, 8-dibromo -2, 6-dimethyloctane is pyrolysed to give mainly citronellyl bromide; (12), (13) 2, 8-dibromo -2, 6-dimethyloctane and sodium acetate give citronellyl acetate; (14) refluxing 2, 8-dibromo-2, 6-dimethyloctane with water gives citronellyl bromide; (15) 2, 8-dibromo -2, 6-dimethyloctane, Ca(OH)2 and water give 8-bromo -2-hydroxy -2, 6-dimethyloctane; (16) citronellyl esters are obtained from 2, 8-dibromo-2, 6-dimethyloctane and salts of carboxylic acids; (17) 2-chloro-8-bromo -2, 6-dimethyloctane, KOH and isopropanol give citronellyl isopropyl ether; (18) 2-chloro -8-bromo -2, 6-dimethyloctane is pyrolysed to citronellyl bromide; (19) the dibromodimethyloctane is similarly pyrolysed; (20), (21) 2-chloro -8-bromo-2, 6-dimethyloctane and Ca(OH)2 or sodium acetate give citronellyl bromide; (22) 2-chloro -8-bromo -2, 6-dimethyl-octane, KOH and isopropanol yield citronellyl bromide and citronellyl isopropyl ether; (23) 8-bromo -2, 6-dimethyloctan -2-ol and sodium acetate yield 2-hydroxy -2, 6-dimethyloct- 8-yl acetate, which is hydrolysed to 2, 6-dimethyl-octane -2, 8-diol; (24) 2-chloro -8-bromo -2, 6-dimethyloctane and sodium acetate yield citronellyl acetate and hydrocarbons (including 2, 6-dimethyl -2, 7-octadiene). Other products are obtained in various examples in small amounts. Specifications 859,567 and 886,763 are referred to.ALSO:A product consisting of about 50% citronellyl acetate and 50% hydrocarbons (including 2,6-dimethyl-2,7-octadiene is obtained by reacting 2 - chloro - 8 - bromo - 2,6 - dimethyloctane with sodium acetate at 230 DEG  C. (Example 24).  Specifications 859,567 and 886,763 are referred to.