摘要
This paper determined the association degree of n-BuLi and polybutadinyllithium(PBLi)by UV spec-trometry and viscometry.The experimental results of UV spectrometric analysis showed that the associationdegree of n-BuLi as well as PBLi is dependent mainly on their concentration in solutions;there may be specieswith three and two degrees of association in cyclohexane solvent respectively for n-BuLi and PBLi,i.e.the asso-ciation degree for the former is equal to 2,4 and 6;and for the latter it equals to 2 and 4.Similarly,the experi-mental results obtained by viscometric measurement showed that the average association degree N of PBLiin cyclohexane changed from 2 to 4 with increasing of its concentration in solution and decreased with addi-tion of a small amount of polar additive into the above mentioned system.Furthermore,in pure polar solvent,such as dimethoxyethane(DME),tetrahydrofuran(THF)or dioxane(DOX),PBLi is completely dissociatedinto monomeric species;however,in pure diethyl ether,due to its weak polarity a part of associated species stillcan be found.Generally speaking,all of the above results were consistent with the results of kinetic studies in-vestigated by us before.
This paper determined the association degree of n-BuLi and polybutadinyllithium(PBLi)by UV spec- trometry and viscometry.The experimental results of UV spectrometric analysis showed that the association degree of n-BuLi as well as PBLi is dependent mainly on their concentration in solutions;there may be species with three and two degrees of association in cyclohexane solvent respectively for n-BuLi and PBLi,i.e.the asso- ciation degree for the former is equal to 2,4 and 6;and for the latter it equals to 2 and 4.Similarly,the experi- mental results obtained by viscometric measurement showed that the average association degree N of PBLi in cyclohexane changed from 2 to 4 with increasing of its concentration in solution and decreased with addi- tion of a small amount of polar additive into the above mentioned system.Furthermore,in pure polar solvent, such as dimethoxyethane(DME),tetrahydrofuran(THF)or dioxane(DOX),PBLi is completely dissociated into monomeric species;however,in pure diethyl ether,due to its weak polarity a part of associated species still can be found.Generally speaking,all of the above results were consistent with the results of kinetic studies in- vestigated by us before.
