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Edwards, John Duncan (1956) Interaction of boron trichloride with alcohols and ethers containing chlorine. Doctoral thesis, Northern Polytechnic.
Further to the work of Gerrard Lappert on the properties of borates and alkoxy-boron chlorides in unsubstituted alkyl systems, the influence of chlorine substituion in the alkyl group has been investigated, more particularly with reference to the thermal stabilities of the and dichloroboronites and chloroboronates.
The following systems were investigated: 2-chloroethyl, 3-chloropropyl and 4-chlorobutyl. With the exception of 4-chlorobutyl dichloroboronite, chlorine substitution was found to increase the thermal stabilities of the chloroesters. Explanations are offered to account for this behaviour. Disproportionation of the chloroesters appeared to be more facile than in the unsubstituted systems. Pyridine complexes of the chloroesters were prepared.
Leading from earlier work concerned with the direction of fission of mixed ethers under the influence of boron trichloride, the reaction of boron trichloride with chlorinated alkyl ethers has been investigated.
The following ethers, methyl 2-chloroethyl, ethyl 2- -chloroethyl, 2,2-dichlorodiethyl and monochlorodimethyl formed 1:1 complexes with boron trichloride. No complex was formed between boron trichl ether. oride and l,l-dichlorodimethyl The 2-chloroethyl ether complexes, the thermal stabilities of which were determined, decomposed on heating.to give 2-chloroethyl dichloroboronite and alkyl chloride. Ether fission was in one direction only. On heating some dissociation of the 2,2-dichlorodiethyl complex into the ether and boron trichloride was also observed. With pyridine or n-butanol the ethers were liberated from the complexes.
On being heated in the presence of excess of the ether the monochlorodimethyl ether complex afforded some 1,1-di- chloromethyl ether.
An investigation into the reactions of cyclic ethers with boron trichloride has also been made.
With boron trichloride tetrahydropyran and tetrahydro- furan both formed 1:1 complexes; thermal decomposition of these led to the appropriate dichloroalkanes, boron tri- chloride and boron trioxide. With the tetrahydropyran com- plex pyridine liberated the ether. With the tetrahydro-furan complex n-butanol liberated the ether, but with pyridine, monopyridine-4-chlorobutyl dichloroboronite resulted. Both ether complexes in the presence of excess of the corresponding ethers gave derivatives of 4-(4-chloro-butoxy)-1--butanol and 5-(5-chloropentoxy)-1-pentanol respectively.
Ethylene oxide, propylene oxide and epichlorohydrin formed no complexes with boron trichloride, but afforded immediately 2-chloroalkyl dichloroboronites. Derivatives of 2-(2-chloroethoxy)-ethanol resulted from a certain experiment with ethylene oxide and similar evidence of polymerisation was forthcoming in experiments with epichlorohydrin. Fission of epichlorohydrin afforded none of the primary alkyl dichloroboronite. Fission of propylene oxide afforded a mixture of primary and secondary dichloroboronites. Trimethylene oxide was extensively polymerised in the presence of boron trichloride; there was no evidence of complex formation.
Complexes were formed between isobutyl n-butyl and di-n-butyl ethers and boron trichloride. Even at -80º, sec.-octyl ethyl ether decomposed out the formation of a stable complex.
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