Linked Life Data

18444619

Source:http://linkedlifedata.com/resource/pubmed/id/18444619

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
20
pubmed:dateCreated
2008-5-15
pubmed:abstractText
Chromium salen derivatives in the presence of anionic initiators have been shown to be very effective catalytic systems for the selective coupling of oxetane and carbon dioxide to provide the corresponding polycarbonate with a minimal amount of ether linkages. Optimization of the chromium(III) system was achieved utilizing a salen ligand with tert-butyl groups in the 3,5-positions of the phenolate rings and a cyclohexylene backbone for the diimine along with an azide ion initiator. The mechanism for the coupling reaction of oxetane and carbon dioxide has been studied. Based on binding studies done by infrared spectroscopy, X-ray crystallography, kinetic data, end group analysis done by (1)H NMR, and infrared spectroscopy, a mechanism of the copolymerization reaction is proposed. The formation of the copolymer is shown to proceed in part by way of the intermediacy of trimethylene carbonate, which was observed as a minor product of the coupling reaction, and by the direct enchainment of oxetane and CO 2. The parity of the determined free energies of activation for these two processes, namely 101.9 kJ x mol (-1) for ring-opening polymerization of trimethylene carbonate and 107.6 kJ x mol (-1) for copolymerization of oxetane and carbon dioxide supports this conclusion.
pubmed:language
eng
pubmed:journal
pubmed:status
PubMed-not-MEDLINE
pubmed:month
May
pubmed:issn
1520-5126
pubmed:author
pubmed:issnType
Electronic
pubmed:day
21
pubmed:volume
130
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
6523-33
pubmed:year
2008
pubmed:articleTitle
Mechanistic studies of the copolymerization reaction of oxetane and carbon dioxide to provide aliphatic polycarbonates catalyzed by (Salen)CrX complexes.
pubmed:affiliation
Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA. djdarens@mail.chem.tamu.edu
pubmed:publicationType
Journal Article