ISSN:
0360-6376
Keywords:
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The initiation reaction of 1,1-diphenylethylene (DPE) dimerization by TiCl4 in dichloromethane has been studied at -30 and -70°C in the presence and absence of added cocatalyst. When water was added to the medium, the concentration of active centers was proportional to cocatalyst concentration. When carbocations R+ are formed without a cocatalyst, their usually low concentration depends on initial concentrations of reagents; thus |R+| ∝ |C|0/|M|0, which indicates that the olefin has an inhibiting effect. The simplest hypothesis applicable to these two observations is the existence of a secondary reaction parallel to initiation which traps the initiator in an inactive form; for example, as a complex with the monomer. The two kinetic schemes, which are proposed according to the stoichiometry of the inactive complex (bimolecular C,M or trimolecular C,M2), support mechanisms that would involve solvent cocatalysis, electronic transfer, or direct addition of TiCl4 on the monomer double bond. Consideration of these rival theories reveals that the most likely is the direct addition of TiCl4 on monomer, but unfortunately the known instability of the corresponding organotitanium intermediates does not allow their characterization.
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1978.170161201
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