6533b86dfe1ef96bd12c9ea9
RESEARCH PRODUCT
false
Miroslav JanataLubomír LochmannAxel H. E. Müllersubject
Reaction mechanismClaisen condensationchemistry.chemical_compoundAnionic addition polymerizationPolymerizationChemistryDimerPolymer chemistryMolar mass distributionTrimerSolution polymerizationdescription
The anionic polymerization of tert-butyl acylate (tBuA) initiated by tert-butyl α-lithioisobutyrate was investigated in THF at 25°C. The individual oligomers were isolated and characterized by UV, IR and NMR spectroscopy. The distribution of products was determined in the range of reaction times 0,02 s ≤ t ≤ 1800 s. The oligomerization is extremely fast. Even after 0,02 s at -30°C, no residual monomer could be detected. After short reaction times the reaction mixture almost exclusively consists of linear oligomers of tBuA. This indicates that there is no termination reaction by Claisen condensation during polymerization. Nevertheless, the molecular weight distribution is rather broad (Mw/Mn = 2,15). The very large amount of dimer observed is an indication of its low reactivity. A two-state mechanism is proposed to account for the high polydispersity. Only after longer reaction times side products are formed by Claisen condensation (“back-bitting”). The termination product of the trimer is an enolized cyclic β-ketoester.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 1990-10-01 | Die Makromolekulare Chemie |