摘要:
The reactions of tetrabutyltitanate (TBT) with alcohols have been studied using IR, Raman, and NMR spectroscopy. It has been shown that TBT is associated and has a centrosymmetrical structure. In nonpolar solvents (CCl4, cyclohexane) the associates do not break down on dilution. In the presence of butanol breakdown of the associates occurs accompanied by a reduction in the number, and even the disappearance, of bridging alkoxy groups. C-13 NMR results show that in mixtures of TBT and alcohols two types of exchange reaction take place simultaneously: between terminal and bridging alkoxy groups, and between TBT and the alcohol. In the case of n-BuOH the first type of exchange is retarded as the temperature is reduced to 283 K but the second is unaffected right down to 213 K. IR results show that alcohols form complexes with TBT in which the alcohol is bonded by a H-bond to the oxygen of the alkoxy group of the TBT and by the oxygen atom to the Ti of a second molecule of TBT. For the exchange reaction between TBT radicals and n-C7H15OH in a binary mixture of 1:1 composition at 293 K, IR spectroscopy showed the degree of conversion in terms of alcohol to be 65% and the equilibrium constant K(e) = 3.4. For MeOH in CCl4 solution the conversion amounted to around 100%.