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Cooper, Sheila (1961) Interaction of boron thihalides with di-oxygen ethers. Doctoral thesis, Northern Polytechnic.
In continuation of work already carried out on the fission of ethers by boron trihalides at the Northern Polytechnic and elsewhere the reactions between boron trichloride and 1,4 dioxane, 1,3-dioxolane, 1,4-dioxene, 2,3-dichloro -1,4-dioxane, 1,3-dioxane, catechyl dime thylene ether, catechyl trimethylene ether and 2-methyl-benz-1,4-dioxen have now been investigated. In addition the reactions of boron tribromide with 1,4-dioxane and 1,3-dioxolane were studied. When ring fission was accompanied by the formation of dichloroborinates, chloroboronates and borates, the properties of these esters were also studied.
1,4-Dioxane formed two solid complexes with boron trichloride which were stable at room temperature. Ring fission occurred at the melting points of these complexes to give 1,2-dichloroethane, di-2-chloroethyl chloroboronate, tri-2-chloroethyl borate and boric oxide. The proportions of these boron esters and 1,2-dichloroethane depended on experimental conditions.
Boron tribromide formed a complex with 1,4-dioxane which decomposed to give either 1,2-dibromoethane and boric oxide, or 1,2-dibromoethane and 2-bromoethyl metaborate.
1,3-Dioxolane did not form a complex with boron trichloride or boron tribromide, but both of these trihalides caused ring fission. When one, two or three moles of dioxolane were added to one mole of boron trichloride the products were 2-chloromethoxyethyl dichloroborinate, di-(2-chloromethoxyethyl) chloroboronate and tri-(2-chloromethoxyethyl) borate respectively.
Attempted distillation of tri-(2-chloromethoxyethyl) borate resulted in the formation of di-(1,2-chloromethoxy)-ethane and 2-chloromethoxyethyl ethylene borate, and attempted distillation of 2-chloromethoxy-ethyl dichloroborinate resulted in disproportionation.
2,3-Dichloro-1,4-dioxane did not react with boron trichloride even at 80-100°, whilst 1,4-dioxene reacted vigorously at low temperatures. One, two or three moles of 1,3-dioxane react with one mole of boron trichloride to give 3-chloromethoxypropyl dichloroborinate, di-(3-chloromethoxypropyl) chloroboronate and tri-(3-chloromethoxypropyl) borate respectively.
Although catechyl dimethylene ether and 2-methyl-benz-1,4-dioxen appeared to form complexes at -80°, complete dissociation occurred at room temperature and atmospheric pressure. Catechyl trimethylene ether formed a 1:1 complex with boron trichloride which had a limited stability at room temperature.
The results of the interaction of boron trichloride with these dioxygen ethers can be correlated with the nucleophilic power of the ethereal oxygen atoms.
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