DSC

2473's picture

Synthesis and NMR Characterization of 6-Phenyl-6-Deoxy-2,3-Di-O-Methylcellulose

Journal Title, Volume, Page: 
Polymers for Advanced Technologies Volume 13, Issue 6, pages 413–427
Year of Publication: 
2002
Authors: 
Othman Hamed
Sucrochemistry Research Group, Hawaii Agriculture Research Center, New Orleans Office, Located at the SRRC, USDA-ARS, New Orleans, LA 70124, USA
Current Affiliation: 
Department of Chemistry, Faculty of Science, An-Najah National University, Nablus, Palestine
David L. Winsor
Sucrochemistry Research Group, Hawaii Agriculture Research Center, New Orleans Office, Located at the SRRC, USDA-ARS, New Orleans, LA 70124, USA
Dr Navzer (Nozar) D. Sachinvala
Cotton Textile Chemistry Research Unit, Southern Regional Research Center (SRRC), USDA-ARS, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA
Walter P. Niemczura
Department of Chemistry, University of Hawaii at Manoa, 2545 The Mall, Honolulu, HI 96822, USA
Karol Maskos
Coordinated Instrumentation Facility, 604 Lindy Boggs Building, Tulane University, New Orleans, LA 70118, USA
Tyrone L. Vigo
Cotton Textile Chemistry Research Unit, Southern Regional Research Center (SRRC), USDA-ARS, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA
Noelie R. Bertoniere
Cotton Textile Chemistry Research Unit, Southern Regional Research Center (SRRC), USDA-ARS, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA
Preferred Abstract (Original): 

Cellulose (1) was converted for the first time to 6-phenyl-6-deoxy-2,3-di-O-methylcellulose (6) in 33% overall yield. Intermediates in the five-step conversion of 1 to­6 were: 6-O-tritylcellulose (2), 6-O-trityl-2,3-di-O-methylcellulose (3), 2,3-di-O-methylcellulose (4); and 6-bromo-6-deoxy-2,3-di-O-methylcellulose (5). Elemental and quantitative carbon-13 analyses were concurrently used to verify and confirm the degrees of substitution in each new polymer. Gel permeation chromotography (GPC) data were generated to monitor the changes in molecular weight (DPw) as the synthesis progressed, and the compound average decrease in cellulose DPw was ∼ 27%. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to characterize the decomposition of all polymers. The degradation temperatures ( °C) and percent char at 500 °C of cellulose derivatives 2 to 6 were 308.6 and 6.3%, 227.6 °C and 9.7%, 273.9 °C and 30.2%, 200.4 °C and 25.6%, and 207.2 °C and 27.0%, respectively. The glass transition temperature (Tg) of­6-O-tritylcellulose by dynamic mechanical analysis (DMA) occurred at 126.7 °C and the modulus (E′, Pa) dropped 8.9 fold in the transition from −150 °C to + 180 °C (6.6 × 109 to 7.4 × 108 Pa). Modulus at 20 °C was 3.26 × 109 Pa. Complete proton and carbon-13 chemical shift assignments of the repeating unit of the title polymer were made by a combination of the HMQC and COSY NMR methods. Ultimate non-destructive proof of carbon–carbon bond formation at C6 of the anhydroglucose moiety was established by generating correlations between resonances of CH26 (anhydroglucose) and C1′, H2′, and H6′ of the attached aryl ring using the heteronuclear multiple-bond correlation (HMBC) method. In this study, we achieved three major objectives: (a) new methodologies for the chemical modification of cellulose were developed; (b) new cellulose derivatives were designed, prepared and characterized; (c) unequivocal structural proof for carbon–carbon bond formation with cellulose was derived non-destructively by use of one- and two-dimensional NMR methods. Copyright © 2002 John Wiley & Sons, Ltd.

Syndicate content