Clinton P. Wade

Effect of base concentration upon the reactivities of the hydroxyl groups in methyl d-glucopyranosides

Abstract The anomeric methyl D -glucopyranosides were treated with N,N-diethylaziridinium chloride in various molarities of aqueous sodium hydroxide at variable ionic strength and constant ionic strength. It was found that the extent of reaction of the hydroxyl groups at C-2, C-3, and C-4 decreased with increasing concentration of base. Reaction at the C-6 hydroxyl group remained essentially constant with increasing concentration of base. Neither varying the ionic strength nor the concentration of reagent affected the distribution of substituents at any given concentration of base.

Selective Accessibilities of Hydroxyl Groups in the Microstructure of Cotton Cellulose1

The reactions of 2-chloroethyldiethylamine with the hydroxyl groups at C-2, C-3, and C-6 of the d-glucopyranosyl unit of cotton cellulose were investigated as a means of evaluating the relative accessibilities of these hydroxyl groups in heterogeneous reactions of fibrous cellulose. The relative rate constants for reactions of the individual types of hydroxyl groups were determined from reactions of cellulose in solution and from reactions of disordered cellulose in heterogeneous systems. Quantitative determinations of the distributions of 2-(diethylamino)ethyl substituents in the mono-substituted d-glucopyranosyl units involved hydrolysis of the chemically modified cellulose to glucose and substituted glucoses followed by gas-liquid chromatographic analysis. The relative accessibilities of the hydroxyl groups at C-2 and C-3 vs those at C-6 were estimated for crystalline celluloses by employing the relative rate constants (noted above) together with the experimentally measured distributions of substituents resulting from heterogeneous reactions of crystalline celluloses and appropriate kinetic expressions. The relative accessibilities of the hydroxyl groups at C-2, C-3, and C-6 in cellulose in strong mercerizing media approach those of cellulose in solution. In media of lower concentration of sodium hydroxide (i.e., 4 N or 13.9%), selective accessibilities of the individual types of hydroxyl groups become evident, and these selective accessibilities become pronounced in sodium hydroxide solutions of still lower concentrations (e.g., N and 2 N).

The Relative Reactivities of the Hydroxyl Groups of Cotton Cellulose—A Progress Report1

Major preceding studies of the distribution of substituents in cellulose have been reviewed. Over-all results indicate that the highest degree of reaction occurs at the hydroxyl group on C-2 in the case of the irreversible Williamson syntheses involving reagents of small molecular size. Pronounced preferential reaction occurs at the hy droxyl group on C-6 in the case of reversible reactions and with increasing molecular size of reagent. The relative reactivities of the hydroxyl groups on C-2, C-3, and C-6 of the D(1→4)- β-glucopyranosyl unit of cotton cellulose have been explored with three chemical agents. Predominant reaction of cotton cellulose occurs at the primary hydroxyl group on C-6 in the case of the reversible Michael addition of methyl vinyl sulfone (i.e., 2-0- : 3-0- : 6-0- = 0.20: 0.03: 1.00), at the hydroxyl groups on C-2 and C-6 in the case of the irreversible reaction with diethylaminoethyl chloride (1.27 : 0.35 : 1.00), and at the hydroxyl groups on C-6 and C-2 in the case of the irreversible Williamson synthesis with sodium allyl sulfate (0.7:0.2:1.0). The D-(1→4)-α-glucopyranosyl unit of dextrin (employed as a soluble model compound for cellulose) undergoes reversible esterification with formic acid most rapidly and to the highest equilibrium level at the primary hydroxyl group on C-6.

Structure of Reagent Residues in Cotton Cellulose Modified with Tris(1-aziridinyl)phosphine Oxide

Several samples of tris(1-aziridinyl)phosphine oxide (APO)-modified cotton were prepared with 5.8-14.6% APO in corporation. The samples were degraded by acid hydrolysis and attempts were made to isolate the expected 0-(2-amino ethyl)-D-glucopyranoses and 0-[N-(2-aminoethyl)-2-aminoethyl]-D-glucopyranoses by a variety of techniques. Neither of these glucose derivatives could be detected in the hydrolyzates; however, the hydrolyzates were found to contain a considerable quantity of ethanolamine along with N-(2-aminoethyl)ethanolamine and complex products resulting from reaction of the functional group at C-1 of glucose and the amino compounds derived from the APO during acid hydrolysis. The ethanolamine in the hydrolyzates of two samples of APO-modified cotton was estimated to account for about 85% of the total nitrogen in the samples. The N-(2-aminoethyl)ethanolamine was estimated to account for about 5% of the original nitrogen. The remaining 10% was in the form of polyethylenimines, N-glucosylamine complexes, and glucose substituents.

Substantivity of Polyethylenimines on Cotton Fabric

Samples of cotton print cloth were impregnated with 10% solutions of polyethylenimines of various molecular weights, line-dried or oven-dried, and then subjected to ten standard laundering and drying cycles. Analysis for retention of the polyethylenimine (PEI) on cotton fabric through a series of ten laundering cycles showed that substantivity increased with increasing molecular weight of PEI. The effect of oven-drying of PEI-cotton fabric was to increase the retention of PEI over that on line-dried samples; the magnitude of the increase was tmoportional to the moledular weight of the PEI. Fabric properties are described.

Enzymatic Hydrolysis as a Source of Structural Information on Cellulose

An apparatus and a procedure are descrihed to facilitate saturation of accessible surfaces of solid cellulose with cellulase and to facilitate removal of inhibiting byproducts from the sphere of reaction. Fibrous cotton cellulose (lattice I) was observed to undergo enzymatic hydrolysis (cluture filtrate from T. Viride, 50°C) in a rate curve similar to that resulting from mineral acid hydrolysis (2.5 N HCl, reflux) but with a time scale greater by a factor of 24. Other similarities be tween enzymatic and mineral acid hydrolyses of this fibrous cellulose are brought out.

N,n-diethylaziridinium chloride as a coreactant catalyst for reactions of n-methylol reagents with cellulose

The use of N,N-diethylaziridinium chloride (DAC) as a coreactant catalyst for the reaction of cellulose with several N-methylol compounds has been investigated. This catalyst was effective in promoting reaction between cotton and all of the four methylol derivatives tested but especially effective in promoting the reactions of dimethylolethyleneurea and methylated trimethylolmelamine with cotton cellulose. These two cross-linking agents could be used in a delayed- cure process with DAC as the catalyst. Little reaction occurred with either of these reagents during delay periods up to 33 days and no increases in recovery angles were found in the delayed and uncured samples. The delayed-but-cured samples showed crease-recovery angles equal to those achieved in immediate cures.

Preparation of whole-fiber cotton gel-filtration chromatography columns

Abstract Methods of preparing whole-fiber gel-filtration columns are described. Reproducible results were obtained with columns prepared by packing with randomized fiber mat type discs (such as cut from absorbent cotton mat rolls). Results from these columns compared favorably with Sephadex columns. The columns had a useful life exceeding one year. Techniques for reducing void volume and increasing the accessible pore volume are described.

Neighboring-group effects in the reactivities of hydroxyl groups in d-glucopyranosides

Abstract Glucosides having the hydroxyl groups at C-2 and C-3 individually substituted were treated with N , N -diethylaziridinium chloride in the presence of concentrations of sodium hydroxide ranging from 0.1 m to 6.0 m . Substitution of the hydroxyl group at C-2 greatly enhances the reactivities of the hydroxyl groups at C-3 and C-4 in dilute base but has less effect in more-concentrated base. Substitution of the hydroxyl group at C-2 has little effect upon the reactivity of the hydroxyl group at C-6. Substitution of the hydroxyl group at C-3 depresses the reactivity of the hydroxyl group at C-2 throughout the range of base concentrations, but this substitution enhances the reactivity of the hydroxyl group at C-6 to a great extent in dilute base and to a much smaller extent in the more concentrated base. Proposed explanations for these results are discussed.

Recent Developments in the Chemistry of Cellulose which Pertain to the Cross-Linking of Cotton1

The distributions of sites of attachment of substituents or cross linkages (a) at the 2–0-, 3–0-, and 6–0-positions of the d-glucopyranosyl units, (b) along the molecular chains of cellulose, (c) on or in the microstructural units, and (d) within the fiber cross sections are reviewed in order to develop perspective for the factors that influence and control these distributions. Among the factors determining the site of attachment in the d-glucopyranosyl unit are: (1) the type of reaction (e.g., reversible or nonreversible), (2) the specific nature of the reagent (e.g., molecular size), and (3) the medium from which the reagent is introduced. Means of controlling this distribution are discussed. There is no available information on the distributions of linkages introduced along the molecular chains of cellulose from reactions that occur without disruption of the crystalline order. It is evident, however, that, even under these conditions, every molecule in the cellulose matrix has one or more accessible segments along its chain. Measurements that are specific to the distribution of substituents among the total d-glucopyranosyl units, but which are applicable, in first-order approximation, to the units along the molecular chain, are discussed in connection with reactions conducted in mercerizing media. Evidence indicative of reactions occurring on the surfaces of highly ordered micro-structural units (microfibrils or bundles of microfibrils) has been obtained from measurement of the distribution of substituents introduced into the d-glucopyranosyl units of cotton cellulose under nonmercerizing conditions. Penetration within these units is evident under mercerizing conditions of reaction. An interrelationship between the site of attachment in the d-glucopyranosyl unit and the site of reaction in the microstructural unit is discussed. At the fiber level of structure, the complex interplay between rate of chemical reaction and rate of diffusion into the fibers is considered. Gross variations of distribution of substituents or cross linkages in the fiber cross section (from peripheral to uniform) result from changes in the two rates noted. In a case examined in some detail, wrinkle-recovery angles benefit from the more uniform distribution of cross linkages.