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Kinetic and mechanistic investigatio...

Yarbrough, Jason C.

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Kinetic and mechanistic investigations of the copolymerization reaction of carbon dioxide and epoxides, using chromium chloride salen catalysts.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Kinetic and mechanistic investigations of the copolymerization reaction of carbon dioxide and epoxides, using chromium chloride salen catalysts./
Author:	Yarbrough, Jason C.
Description:	240 p.
Notes:	Source: Dissertation Abstracts International, Volume: 64-04, Section: B, page: 1732.
Contained By:	Dissertation Abstracts International64-04B.
Subject:	Chemistry, Inorganic. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3088200
ISBN:	0496359622

Kinetic and mechanistic investigations of the copolymerization reaction of carbon dioxide and epoxides, using chromium chloride salen catalysts.
Yarbrough, Jason C.

Kinetic and mechanistic investigations of the copolymerization reaction of carbon dioxide and epoxides, using chromium chloride salen catalysts. - 240 p.

Source: Dissertation Abstracts International, Volume: 64-04, Section: B, page: 1732.

Thesis (Ph.D.)--Texas A&M University, 2003.

A series of air-stable (salen)CrIIICl complexes, where H2salen = N,N'-bis(3,5-di-t-butylsalicylidene)-1,2-di-(R)-1,2-ethylenediimine, have been shown to be effective catalysts for the coupling of cyclohexene oxide and propylene oxide with CO2, to afford co-poly(cyclohexene carbonate) and co-poly(propylene carbonate), along with various quantities of the associated cyclic carbonate byproduct. The polycarbonate obtained for the reaction of cyclohexene oxide and CO2, mediated by Jacobsen's catalyst (N,N'-bis(3,5-di-t-butylsalicylidene)-1,2-cyclohexanediimino Cr(III) chloride), exhibited >99% CO2 incorporation and a Mn = 8900 g/mol with a polydispersity index (PDI) of 1.2 as determined by gel permeation chromatography. Further, Jacobsen's catalyst proved most active giving turnover number (TON) and turnover frequency (TOF) values of 250 moles of CHO consumed/mole of Cr and 10 mol CHO consumed/mol Cr/hour for reactions carried out at 80°C and 58.5 bar in CO2 pressure. These values increased by threefold upon addition of 5 equivalents of N-methylimidazole relative to [Cr]. The polymer produced was completely atactic as evidenced by 13C NMR spectroscopy. The rate of carbonate chain growth and cyclic carbonate production are linearly dependent on [Cr]. This is demonstrated herein by way of in situ measurements. This was shown to hold for the use of CHO and PO substrates. Investigations of this (salen)CrIII-catalyzed system for the coupling of propylene oxide and CO2 revealed that although cyclic carbonate was the major product at elevated temperatures, reactions carried out at ambient temperature produced predominantly co-poly(propylene carbonate). This characteristic difference between alicyclic and aliphatic substrates was investigated quantitatively by way of variable-temperature in situ measurements. Arrhenius analysis of the thus obtained rate data showed the activation energies for copolymer and cyclic carbonate formation in the PO/CO2 coupling reaction to be 20 kJ/mol greater and 33 kJ/mol lower than that observed for the CHO/CO2 coupling reaction, respectively.

ISBN: 0496359622Subjects--Topical Terms:

517253
Chemistry, Inorganic.

Kinetic and mechanistic investigations of the copolymerization reaction of carbon dioxide and epoxides, using chromium chloride salen catalysts.
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245 1 0 $a Kinetic and mechanistic investigations of the copolymerization reaction of carbon dioxide and epoxides, using chromium chloride salen catalysts.
300 $a 240 p.
500 $a Source: Dissertation Abstracts International, Volume: 64-04, Section: B, page: 1732.
500 $a Chair: Donald J. Darensbourg.
502 $a Thesis (Ph.D.)--Texas A&M University, 2003.
520 $a A series of air-stable (salen)CrIIICl complexes, where H2salen = N,N'-bis(3,5-di-t-butylsalicylidene)-1,2-di-(R)-1,2-ethylenediimine, have been shown to be effective catalysts for the coupling of cyclohexene oxide and propylene oxide with CO2, to afford co-poly(cyclohexene carbonate) and co-poly(propylene carbonate), along with various quantities of the associated cyclic carbonate byproduct. The polycarbonate obtained for the reaction of cyclohexene oxide and CO2, mediated by Jacobsen's catalyst (N,N'-bis(3,5-di-t-butylsalicylidene)-1,2-cyclohexanediimino Cr(III) chloride), exhibited >99% CO2 incorporation and a Mn = 8900 g/mol with a polydispersity index (PDI) of 1.2 as determined by gel permeation chromatography. Further, Jacobsen's catalyst proved most active giving turnover number (TON) and turnover frequency (TOF) values of 250 moles of CHO consumed/mole of Cr and 10 mol CHO consumed/mol Cr/hour for reactions carried out at 80°C and 58.5 bar in CO2 pressure. These values increased by threefold upon addition of 5 equivalents of N-methylimidazole relative to [Cr]. The polymer produced was completely atactic as evidenced by 13C NMR spectroscopy. The rate of carbonate chain growth and cyclic carbonate production are linearly dependent on [Cr]. This is demonstrated herein by way of in situ measurements. This was shown to hold for the use of CHO and PO substrates. Investigations of this (salen)CrIII-catalyzed system for the coupling of propylene oxide and CO2 revealed that although cyclic carbonate was the major product at elevated temperatures, reactions carried out at ambient temperature produced predominantly co-poly(propylene carbonate). This characteristic difference between alicyclic and aliphatic substrates was investigated quantitatively by way of variable-temperature in situ measurements. Arrhenius analysis of the thus obtained rate data showed the activation energies for copolymer and cyclic carbonate formation in the PO/CO2 coupling reaction to be 20 kJ/mol greater and 33 kJ/mol lower than that observed for the CHO/CO2 coupling reaction, respectively.
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650 4 $a Chemistry, Polymer. $3 1018428
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773 0 $t Dissertation Abstracts International $g 64-04B.
790 1 0 $a Darensbourg, Donald J., $e advisor
790 $a 0803
791 $a Ph.D.
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