13C NMR Study on the Distribution of Substituent Groups on Trihydric Alcohol Units in Cellulose Xanthate

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ABSTRACT:An attempt was made to assign a number of peaks, observed in carbonyl region (168-171 ppm) of 13 C{ 1 H} NMR spectra of cellulose acetate (CA), to twelve magnetically different acetyl groups existing in 8 kinds of glucopyranose units constituting CA. CA samples with total degree of substitution ((F)> ranging 0.43 to 2.46 were prepared by acid-hydrolysis of CA with ((F)> =2.92 dissolved in acetic acid. 13 C{ 1 H} NMR measurements were made on these ten CA samples in deuterated dimethylsulfoxide and 14 peaks in total were observed definetely over the whole range of ((F)> from 2.92--0.43. From the spectra of CA samples with highest ((F)> (2.92) and lowest (0.43) carbonyl carbon peaks at C6 , C3, and C2 positions in trisubstituted and monosubstituted glucopyranose units were successfully assigned. Deducing the effect of an acetyl group on the chemical shift of other acetyl groups, and vise versa, based on an empirical rule, 6 carbonyl carbon peaks in 3 kinds of disubstituted glucopyranose units were assigned, Eight average molar fractions ((f,.,,.)> (/= I or O means that a hydroxyl group attached directly at C2 position is or is not substituted and m = I or O means that C3 position is or is not substituted, and n corresponds to C6 position) [i.e., ((f000)>, ((f100)}, · · ·, ((f111 )>] were evaluated from integrated intensity ratios. The probability of substitution at Ck position ((fk)> (k=2, 3, and 6) and ((F)>, both evaluated from the above ((f,,,,0 )> values, fairly agree with those estimated by the conventional NMR method, indicating the validity of the assignment in this paper.

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confidence: 89%

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confidence: 99%

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confidence: 99%

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Determination of the Distribution of the Substituent Group in Cellulose Acetate by Full Assignment of Au Carbonyl Carbon Peaks of 13C{1H} NMR Spectra

Kowsaka¹,

Okajima²,

Kamide³

1988

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“…From systematic analysis on 1 H and 13 C NMR spectra of sodium cellulose sulfate,4 cellulose acetate (CA), 5 -7 sodium carboxymethylcellulose,8 sodium cellulose xanthate (CX), 9 carboxyethylcarbamoylethylcellulose 10 and cyanoethylcellulose, 11 Kamide, Okajima, and their coworkers elucidated <(fk)) (k =2, 3,6), correlation <(fk)) with some physical and physilogical properties. Wu, 12 Clark and Stephenson, 13 and Miyamoto et al 14 estimated, from NMR spectra, <(fk)) of cellulose nitrate and CA.…”

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confidence: 99%

Two-Dimensional Nuclear Magnetic Resonance Spectra of Cellulose and Cellulose Triacetate

Kowsaka¹,

Okajima²,

Kamide³

1988

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ABSTRACT:An attempt was made to give a full assignment, using only NMR information, to all peaks in 1 Hand 13 C NMR spectra for systems of cellulose in 2.5 N NaOD/D2O and of cellulose triacetate (CTA, total degree of substitution 2.92) in deuterated trichloromethane (TCM-d), and in deuterated dimethylsulfoxide (DMSO-d6). For this purpose two-dimensional (2D) homonuclear 1 H shift correlation spectroscopy (COSY), heteronuclear 1 H-13 C shift correlation spectroscopy (C-H COSY), and long-range heteronuclear 1 H-13 C shift correlation spectroscopy (long-range C-H COSY) were applied to the above systems. By COSY 1 H peaks of cellulose/aq. alkali solution were assigned, from lower magnetic field, to H,, H6 , H6 ', (H3 + H4 + H5), and H2 protons, respectively.Here, two unequivalent H6 peaks heavily overlapped in the one-dimensional spectrum were observed very separately in 2D spectrum. By C-H COSY 13 C peaks of cellulose were assigned, from lower magnetic field, to C1, (C3, C4 , C5), C2 , and C6 carbons, respectively. C3 , C4 , and C5 carbon peaks were unable to be assigned separately, due to mutual and heavy overlapping of H3 , H4 , and H5 peaks. For cellulose triacetate, through use of COSY and C-H COSY all peaks in the region of glucopyranose backbone in 1 H and 13 C NMR wre able to be successfully and completely assigned. Long-range C-H COSY confirmed definitely the existence of the close correlationships between acetyl methyl proton and carbonyl carbon at the different carbon positions of CTA, which showed again the validity of the previous assignment with respect to carbonyl carbons (i.e., C6 , C3 , and C2 carbons from lower magnetic field). KEY WORDSCellulose / Cellulose Acetate / Cellulose Triacetate / 13 C NMR / 1 H NMR / Two-Dimensional NMR / Correlation Spectroscopy/ Long-Range Heteronuclear Correlation Spectroscopy/ Recently numerous studies have been published on the high resolution NMR spectra of solutim1.s of cellulose and its derivatives. NMR spectra of cellulose were utilized widely as a method for elucidating the dissolved state of solutes in solvents (i.e., interaction between solutes and solvents) and those of cellulose derivatives were employed for analysis of the average degree of substitution for each three hydroxyl groups «:fk» (k =2, 3, 6) in the glucopyranose unit: For example, Kamide et a/. 1 showed, from 1 H NMR spectra of eellulose in dimethylformamide/chloral/pyridine mixture, that cellulose dissolved in the form of cellulose trichlorate (CTC) in the solution. Gagnaire and his coworkers 2 speculated the dissolved state of cellulose in Nmethylmorpholine-N-Oxide/dimethylsulfoxide (DMSO), methylamine/DMSO, hydrazine/ DMSO, and paraformaldehyde/DMSO by comparing the 13 C chemical shifts in these solutions. Kamide and his collaborators 3 showed that a physically treated cellulose, whose intramolecular hydrogen bondings were de-* To whom all correspondence should be addressed. 1091

“…Kamide and his coworkers evaluated, mainly using NMR method, and for various cellulose derivatives including cellulose acetate (CA), 2 · 3 cellulose sulfate, 4 -6 sodium carboxymethyl cellulose (NaCMC), 6 cellulose xanthate, 7 and carboxyethyl carbamoylethyl cellulose, 8 and demonstrated that some physical and physiological properties are not only a single function of but also functions of (k=2, 3, and 6) and Kowsaka et a!. 9 determined average molar fractions for eight kinds of unsubstituted, partially and fully substituted AHG units of cellulose acetate samples by establishing full assignments of all carbonyl peaks of 13 C{ 1 H} NMR spectra.…”

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confidence: 99%

Determination of Sequence Distribution of Substituted and Unsubstituted Glucopyranose Units in Water-Soluble Cellulose Acetate Chain as Revealed by Enzymatic Degradation

Iijima¹,

Kowsaka²,

Kamide³

1992

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ABSTRACT:An attempt was made to investigate the distribution of substituent groups along the chains of water-soluble, partially substituted cellulose acetate (CA) molecules. For this purpose, two water-soluble CA samples (i.e., one with the total degree of substitution «F)>= 0.88 and the weight-average molecular weight Mw=35900 and the other with «F)>=0.60, and Mw=42000), prepared by acid-hydrolysis of cellulose diacetate (CDA) («F)>=2.46) synthesized by two-step method, were subjected to enzymatic hydrolysis in water solution. The degraded products were fractionated by preparative gel permeation chromatography (GPC) into 50 and 20 fractions, analyzed by analytical GPC and by 13 C NMR to determine peak molecular weight (Mp) and «F)>, respectively. «F)> of water-soluble components in the degraded products was nearly constant ( = 1.0) and the degree of polymerization DP was in the range 1-7 in both enzymatic hydrolysis experiments. The above characteristics were quantitatively consistent with computer experiments made under the condition of the endo-exo-exo degradation hypothesis. Cleavage of water-soluble CA samples yielded a small portion of water-insoluble CA component with «F)) of 2.48 and 2.45, respectively. The water-insoluble CA component had lower average molecular weight than the water-soluble CA, indicating that highly-substituted cellulose acetate short blocks can exist in water-soluble cellulose acetate chains having lower degree of substitution.