Kinetic Studies of the Thermal cis-to-trans Isomerization of Dioxaphospholanes
作者： Herbert Hommer , Gabriel Cuevas , Barbara Gordillo
DOI: 10.1080/10426500801963822
关键词: Substituent 、 Kinetic energy 、 Chemistry 、 Work (thermodynamics) 、 Cis–trans isomerism 、 Activation energy 、 Epimer 、 Alkoxy group 、 Isomerization 、 Physical chemistry
摘要: By following a previously reported method,1 the synthesis of r-2-alkoxy-cis-4-cis-5-dimethyl-1,3,2-λ3-dioxaphospholanes ligands (1 and 3) was carried out. The purpose this work is kinetic study inversion barrier at phosphorus for 1 3 comparison with already informed dioxaphospholane 2. measurements thermal isomerization cis-to-trans were performed by 31P NMR spectroscopy, observing first order kinetics both compounds. energy activation (Ea) epimerization compounds cis-1 cis-3 calculated to be 16.0 ± 0.6 11.8 0.8 kcal/mol, respectively. values thermodynamic parameters transition state (Δ H≠, Δ S≠, G≠) suggest that not only depends on spatial requirements alkoxy substituent but also entropic effects. H°, S°, G° evaluated they show cis isomers are preferred from enthalpic point view, e...
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