58797-30-1Relevant academic research and scientific papers
Regioregular and regioirregular oligoether carbonates: A 13C{1H} NMR investigation
Byrnes, Matthew J.,Chisholm, Malcolm H.,Hadad, Christopher M.,Zhou, Zhiping
, p. 4139 - 4145 (2007/10/03)
Oligoether carbonates R(PO)nOCO2(PO)nR, where R = Me, Et, or H, PO = propylene oxide ring-opened unit, and n = 1, 2, 3, 4, ～10, and ～30, have been prepared and characterized by ESI/MS or MALDI/MS and 13C{1H} NMR spectroscopy in addition to 1H NMR, DEPT, COSY, and HMQC. The propylene oxide (PO) units have been derived from S-PO and rac-PO. The compounds have been examined as potential models for polyether carbonate units in poly(propylene carbonate). For HH junctions, assignments of isotactic (i) and syndiotactic (s) diads and iii, iis/sii, sis, isi, ssi/iss, and sss tetrads are unequivocal. Assignments at the hexad level are limited. For higher oligoether carbonates, i.e., n ～ 10 or ～30, only the i and s diad sensitivity is possible at 150 MHz 13C{1H} NMR. Calculations on the compounds MeOCH 2CHMeOCO2CHMeCH2OMe (RR (i) and SR (s)) and MeOCO2CH2CHMeOCO2CHMeCH2OCO 2-Me were carried out employing density functional theory (DFT) at the B3LYP/6-31G(d) level for geometry optimization and the B3LYP/6-311+G(2d,p) level for NMR calculations. These results are compared with the experimental work and structures of dimethyl carbonate.
13C-N.M.R.-SPECTRAL AND RELATED STUDIES ON THE DISTRIBUTION OF SUBSTITUENTS IN O-(2-HYDROXYPROPYL)CELLULOSE
Lee, Dae-Sil,Perlin, Arthur S.
, p. 1 - 20 (2007/10/02)
Information about the degree of substitution at individual oxygen atoms of O-(2-hydroxypropyl)cellulose, and the total molar substitution, was obtained from 13C-n.m.r. spectra of the intact polymer and of its hydrolyzate.On the basis of their 13-CH3 chemical-shifts, O-(2-hydroxypropyl) (HOPr) substituents occurring singly, or as terminal units of substituent chains, were radily distinguished from inner HOPr units of chains.Differentiation between monomeric HOPr units and longer chains located at O-2 of D-glucosyl residues was effected by the transformation of appropriatly substituted sugars in the hydrolyzate into 1,2-cyclic acetals incorporating a 2-O-(2-hydroxypropyl) group.Similarly, the pattern of substitution at O-6 of D-glucosyl residues was determined, through selective degradation, from the identity of HOPr derivatives of ethylene glycol, representing C-5 and C-6 of the residues.Overall, it was found that, although O-2 and O-6 are more readily substituted than O-3, the rate at which each, initially introduced, HOPr substituent is converted into a dimeric structure is not materially affected by its location.Also described are the synthesis and the n.m.r. spectra of several HOPr derivatives of D-glucose, and of simple alkanols that served as model compounds.
