Effect of ferric chloride on acid hydrolysis of viscose rayon

A comparison between the fine structure of viscose hydrocelluloses prepared by acid hydrolysis of viscose fibers in the absence and presence of ferric chloride is given. The results indicate that ferric chloride has little effect on the change in x-ray crystallinity indices accompanying acid-hydrolysis of the fibers. On the other hand, specific volume results show that the inner fine structure of hydrocelluloses prepared by hydrolyzing the fibers with free acid differs from that for hydrocelluloses prepared with an HCl-FeCl₃ reagent.     

Effect of acid hydrolysis on accessibility of micropores and thermal transition of viscose rayon

The changes in micropores accessible to toluene but inaccessible to decalin taking place during acid hydrolysis of viscose rayon were followed by specific volume measurements. The results show that these changes at the different stages of hydrolysis are of different order and dependent on the hydrolytic conditions. Also, it was found that the decalin molecules, which are larger than toluene molecules, could not follow the gradual disappearance of the thermal transition of viscose rayon with the progress of hydrolysis.     

Effect of the fine structure of viscose hydrocellulose on its adsorption properties

From the heat of wetting in water and the iodine adsorption measurements of certain hydrolytic residues prepared by the acid hydrolysis of viscose rayon in the absence and presence of FeCl₃, a comparison was made between their water adsorption capacity and iodine molecules. The data obtained revealed first that in the initial stages of acid action of the fibers the adsorption cites accessible to water or iodine molecules decrease to some extent, depending on the hydrolytic condition. Second, in the inner fine structure of the various residues examined, there remains a high proportion of cites accessible to water molecules that are inaccessible to iodine. These results are explained by the fact that the water molecules can penetrate the submicroscopic structure of cellulose chains by molecular forces and the swelling effect.     

Assessment of the state of order of hydroxyl groups and of molecular segments in hydrocellulose

Through a study of the selective distribution of substituents introduced into hydrocellulose from reaction with N,N-diethylaziridinium chloride, the change in selective availability of hydroxy groups at C-2, C-3, and C-6 has been followed as a function of duration of hydrolysis to form the hydrocellulose. The hydrocellulose formed at a particular duration of hydrolysis showed maximum selective availability of hydroxyl groups; this was found to coincide with minimum moisture regain and minimum breadth at half height for 101 , 101, and 002 peaks in x-ray diffractograms. These points are discussed in terms of the structures of the hydrocelluloses at various stages of hydrolysis and in terms of the sequence of changes which is now associated with the conversion of fibrous cotton to “exemplar hydrocellulose,” i.e., the hydrocellulose having the highest degree of crystalline order, and subsequently, to less highly ordered hydrocelluloses.     

中国乌头的研究XIV: 紫草乌碱甲的化学结构的研究

从云南紫草乌(Aconitum delavayi Franch)中所得的紫草乌碱甲(delavaconitine)是具有麻醉作用的新的二萜类生物碱,其分子式应更正为C29H39O6N.经水解、乙酰化、热解和异构化等化学反应及紫外光谱、红外光谱、质谱及^1H和^1^3C核磁共振的测定,确定它的化学结构为;其水解产物紫草乌碱甲胺醇(delavaconine)经X射线衍射测定,进一步证实了它的化学结构.     

Effect of acid hydrolysis on the apparent specific volume of viscose rayon

The apparent specific volumes of viscose rayon and its hydrolysis residues, prepared by the action of 0·2 and 1 N HCl at 100°, were measured dilatometrically in the range 5–50° using toluene as displacement medium. The variation of the specific volume at 20° with the progress of hydrolysis showed a characteristic minimum, dependent on the hydrolytic conditions. These results, with those previously obtained from i.r. studies showed that the crystallinity of the fibre increased till 2·5% dissolution, and then decreased. Also, it was found that the second order transition of viscose rayon is primarily a function of its accessibility rather than its DP.     

X-ray and neutron diffraction studies of the crystal and molecular structure of the predominant monocarboxylic acid obtained by mild acid hydrolysis of cyanocobalamin. Part III. Neutron diffraction studies of wet crystals

The molecular structure of the predominant monocarboxylic acid, E2, obtained by mild acid hydrolysis of cyanocobalamin has been determined by neutron diffraction with some support from x-ray diffraction. The undried crystals, formula probably C₆₃H₈₇O₁₅N₁₃PCo l6H₂O, have unit cell parametersa = 14.91(1) A, b = 17.49(l)A, c = 16.41(1)A, β = 104.11(5)°; space group P2₁, Z = 2. The analysis was carried out in two stages with data extending to 1.3 A (1531 terms) and to 1.0 A (2993 terms) respectively. It was initiated by the use of coordinates of 84 atoms from the parallel x-ray analysis to phase the first Fourier series. The atomic positions derived from the 1.3 A data set appeared in good agreement with the chemical evidence both on the corrin structure and on the position of the acid group ate. However the analysis by Fourier and least squares methods on the extended data defined the atomic positions much more clearly and showed that diffraction ripples had distorted some of the hydrogen atom positions in the low resolution map. The acid group appeared clearly placed in the higher resolution map at theb position. The positions of disordered atoms in thee chain and some water molecules were checked with the parallel x-ray analysis. It seems most likely to us therefore that this acid is α-(5,6-dimethylbenzimidazolyl)cobamic acida,c,d,g,e pentamide cyanide.     

Effect of alkali pre-treatment on hydrolysis of regenerated cellulose fibers (part 1: viscose) by cellulases

Viscose fabrics were pre-treated with liquid ammonia and NaOH solutions. The pre-treatment was varied in alkali concentration, time and drying conditions. Subsequently, the samples were subjected to cellulase hydrolysis. Microscope and SEM pictures were taken; weight loss, reducing sugar and protein content in solution, water retention value and tensile strength were determined. It was found, that the activity of cellulases is increased for viscose and that short time alkali pre-treatment reduces tensile strength due to changes in the substrate. The drying and drying conditions (wet, line dry of freeze dry) have great impact on the hydrolysis rate. A connection between the rate of protein loss in solution and changed water retention value was established. Weight loss of 80% of cellulose fabric was achieved within 4 h of enzyme hydrolysis.     

Hydration structures of U(III) and U(IV) ions from ab initio molecular dynamics simulations

We apply DFT+U-based ab initio molecular dynamics simulations to study the hydration structures of U(III) and U(IV) ions, pertinent to redox reactions associated with uranium salts in aqueous media. U(III) is predicted to be coordinated to 8 water molecules, while U(IV) has a hydration number between 7 and 8. At least one of the innershell water molecules of the hydrated U(IV) complex becomes spontaneously deprotonated. As a result, the U(IV)-O pair correlation function exhibits a satellite peak at 2.15 A? associated with the shorter U(IV)-(OH(-)) bond. This feature is not accounted for in analysis of extended x-ray absorption fine structure and x-ray adsorption near edge structure measurements, which yield higher estimates of U(IV) hydration numbers. This suggests that it may be useful to include the effect of possible hydrolysis in future interpretation of experiments, especially when the experimental pH is close to the reported hydrolysis equilibrium constant value.     

Molecular chain conformation and crystallite structure of cellulose. I. Fine structure of rayon fibers

A most reasonable folded-chain model for the fine structure of rayons (cellulose II) has been developed through experimental work on a theoretical basis. All the materials uniformly gave a levelling-off DP of about 40, equivalent to a length around 200 Å, for cellulose molecule segments at the early stage of heterogeneous acid hydrolysis when the first minor fraction is scarcely dissolved. Measurements by small-angle and wide-angle x-ray scattering put the crystallite length from various rayon fibers at about 200 Å, without exception. A family of GPC chromatograms, furthermore, on the hydrolyzed cellulose exhibited a single peak considered to represent monodispersed materials. These data suggest that clearly divided sections exist within the microfibril along its axis in a regular manner at an interval of about 200 Å. This cannot be explained in terms of the fringed micelle model. On the other hand, the possibility that cellulose II may have a folded-chain conformation has been demonstrated. A single cellulose molecule is essentially folded back and forth in the (101) plane to form a sheetlike structure. Such a structure is the basic unit that can fit perfectly into the unit cell of cellulose II. The cellulose molecule can achieve a fairly sharp U-turn in the (101) plane, with only one glucose unit of in the half-boat conformation. A crystallite consists of a number of sheets held together by secondary forces in the (101) plane. Accordingly, crystallographically, the crystallites are closely packed at the surface of each fold at its longitudinal edges to make up the cellulose microfibril. According to our model, the oxygen atom of the glucosidic link in the fold, where acid hydrolysis would have to take place, protrudes partially from the surface of the crystallite; a pair of atoms at the folds are then facing each other and are therefore, accessible for hydrolysis. This would explain chain scission of cellulose II at these sites in hydrolysis. This folded-chain model is supported further by other experimental evidence.     

Dielectric study of viscose rayon and viscose hydrocelluloses. II

The effect of temperature on the dielectric properties of viscose fibers as well as of some of its acid-modified residues was investigated. The results obtained show that: first, the change in the fine structure accompanying the acid degradation of the fibers has little, if any, effect on the location of the β peaks at any given temperature; second, the thermal transition of viscose fibers disappears with the late hydrolyzed vacuum-dried residues. These results are discussed in the light of infrared spectra of the OH stretching vibration as well as specific volume data.     

Infra-red study on the oxidation of cotton cellulose,viscose rayon and their hydrolysis residues

The i.r. absorption band at 5·8 μm, characteristic of the CO group resulting from the oxidation of cellulosic fibres, has been used to study the effect of acid hydrolysis on the accessible OH groups of cotton cellulose and viscose rayon. The results obtained in this investigation, and those previously found by measurement of the rate constant of oxidation, show that both the i.r. and the rate constant of oxidation may be used as quantitative measures of the accessible OH groups in the various cellulosic fibres. The effect of temperature on the rate constant of oxidation of some hydrolysis residues was studied. The activation energies of oxidation of the late cotton hydrocellulose and viscose hydrocellulose residues have been found to be 12·2 and 13·3 kcal. respectively.     

Small-angle scattering study of structural changes in the microfibril network of nanocellulose during enzymatic hydrolysis

The hydrolysis of nanofibrillated cellulose (NFC), consisting of individual cellulose fibrils, was followed using small-angle scattering techniques in order to reveal changes in the substrate structure caused by cellulose degrading enzymes. In particular, the nanoscale structure of the network of cellulose fibrils was characterized with the combination of small-angle neutron scattering and small-angle x-ray scattering. In the nanocellulose with higher xylan content, the interfibrillar distance was shown to remain unchanged during enzymatic degradation, whereas the distance increased in the nanocellulose with lower xylan content. The limiting effect of xylan on the hydrolysis and a faster hydrolysis of the more thoroughly fibrillated segments of the NFC network could be observed. Despite the extensive fibrillation of the raw material, however, the hydrolysis was eventually limited by the aggregated and heterogeneous structure of the substrate.     

Morphological and structural changes in a copolymer of glycolide and lactide occurring as a result of hydrolysis

The changes in the structure and morphology of a random copolymer containing 92 mol % glycolide units and 8 mol % lactide units as a function of in vitro hydrolysis have been studied. A number of techniques, such as wide-angle x-ray diffraction, small-angle x-ray scattering, density measurements, infrared spectroscopy, and viscometry were employed in this study. The results showed that the hydrolytic attack was initiated in the amorphous areas of the polymer. After 28 days in the in vitro medium most of the amorphous areas had been chemically converted to lower-molecular-weight species such as oligomers of poly(glycolide-co-lactide). These low-molecular-weight species become water solble and are removed rapidly after day 28. Thus the fiber takes on a Swiss cheese character as the amorphous matter is hydrolyzed and eventually dissolved. As hydrolysis proceeds further, the crystalline areas of the polymer are attacked and eventually removed from the fiber by solubilization. The resulting voids in the fiber are eventually filled by a “collapse” of the structure. The role of the amorphous areas of the polymer in controlling the tensile strength of the suture is discussed.     

Some considerations of the kinetics of the acid hydrolysis of poly- and oligosaccharides. Part III. The disaccharides 2-O-(α-D-glucopyranosyluronic acid)-D-xylose, 2-O-(4-O-methyl-α-D-glucopyrano-syluronic acid)-D-xylose,and 2-O-(4-O-methyl-α-D-glucopyranosyl)-D-xylitol

Rate equations have been formulated for the formation and depletion of the hydrolysis product(s) of the title disaccharides. They are based on the assumptions that (1) the rate of acid hydrolysis of the disaccharides is according to first order, and (2) the rate of depletion of the hydrolysis product(s) is constant in the early periods while it approaches first order in the more advanced stages of the reactions. By using experimental rate data from the literature the rate constants of the hydrolysis of the disaccharides and of the depletion of the hydrolysis product(s) have been computed. The validity of the assumptions underlying the rate equations advanced has been confirmed by (a) the agreement between experimental and calculated values and (b) the similar values for the rate constant of the depletion of xylose formed in the hydrolysis of the two biouronic acids. Also discussed are some implications arising from the magnitude of the hydrolysis rate constant of methylaldobiouronic acid and of the depletion rate constant of xylose in relation to complete hydrolysis of polysaccharides.     

Poly(alkylene oxide) ionomers. XII. Hydrolysis of polymers and copolymers of methyl 10,11-epoxyundecanoate

Ester-substituted oxyethylene polymers and copolymers of methyl 10,11-epoxyundecanoate were prepared with an aluminumalkyl–water coordination initiator system modified with acetylacetone. Poly(ethylene oxide) ionomers, polyelectrolytes, and polycarboxylic acids were obtained by alkaline hydrolysis of the pendant carbomethoxy groups and by neutralizations with acetic acid. The high molecular weight substituted poly(ethylene oxide)s were characterized by spectral, thermal, and dilute solution measurements. The infrared spectra of carboxylate substituted poly(ethylene oxide)s, both homo- and copolymers, show the typical shifts in the carboxyl absorption when going from the ester to the carboxylate group to the free acid. Polymer transitions temperatures, as measured by DSC, changed accordingly. Wide-angle x-ray diffraction measurements strongly suggest the existence of ionic domains in the oxyethylene polymer matrix. Dilute solution properties of the ionomers show typical polyelectrolyte behavior, including a substantial change in viscosity when ionic solute is added.     

Unusually ready hydrolysis of nitrile groups in 1,1,2,2-tetracyanoethane by pyruvic acid

A scheme for the unusually ready selective hydrolysis of three of the cyano groups in 1,1,2,2-tetracyanoethane to 2-cyanoethane-1,1,2-tricarboxamide by the action of pyruvic acid was proposed. Only one cyano group undergoes hydrolysis in the reaction with sodium pyruvate. In the course of this reaction, 2-amino-5-methyl-3, 4-dicyano-4,5-dihydrofuran-4,5-dicarboximide, the structure of which was determined by x-ray diffraction investigation of the monocrystal, is formed. I. N. Ul'yanov Chuvashsk State University, Cheboksary 428015. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1472–1476, November, 1997.     

Studies on steroids. CXXVIII. Separation and determination of bile acids by high-performance liquid chromatography

A method is described for the simultaneous determination of major bile acids by high-performance liquid chromatography without prior hydrolysis. A mixture of bile acids is divided into the free, glyco- and tauro-conjugate groups by thin-layer chromatography. Separation of each group into cholate, ursodeoxycholate, chenodeoxycholate, deoxycholate and lithocholate is attained in two stages on a muBondapak C18 column; first, 0.3% ammonium carbonate-acetonitrile (9:4) is used as a mobile phase for the separation of the last three compounds. Subsequently cholate and ursodeoxycholate are resolved by chromatography in 0.3% ammonium carbonate-acetonitrile (11:4).     

Etching of crystalline poly(ethylene terephthalate) by hydrolysis

Conditions have been found for the etching of poly(ethylene terephthalate) with water so that the crystalline portions alone remain. Initial sample and hydrolysis products are analyzed by extraction of low molecular weight products; density, viscosity molecular weight, and endgroup determination; heating-rate-dependent thermal analysis; low-angle and wide-angle x-ray analysis; and electron microscopy. On hydrolysis of a 67% crystalline polymer at 180°C for about 300 min, almost fully crystalline extended-chain oligomers can be obtained with about 65% yield. The morphology of melt-crystallized poly(ethylene terephthalate) and the melting behavior of oligomer lamellae are discussed.     

1-Aryl-5-carboxymethylhydantoin derivatives. structure of 1-phenyl-2-thio-5-carbomethoxymethylhydantoin

The reaction of aromatic amines with maleic acid or its diethyl ester with subsequent hydrolysis gave N-arylaspartic acids, which were converted to 1-aryl- and 1-aryl-2-thio-5-carboxymethylhydantoins by the action of urea, cyanates, or thiocyanates in an acidic medium. Esterification of the acid products with methanol gave the corresponding carbomethoxymethylhydantoins, which were converted by reduction to tetrahydroimidazole derivatives and by acetylation to acetyl derivatives. Alkylation of the carboxymethylhydantoins with dimethyl sulfate gave 3-methyl derivatives of hydantoins, while alkylation with formaldehyde gave 3-hydroxymethyl derivatives of hydantoins. Data from the x-ray diffraction analysis of 1-phenyl-2-thio-5-carbomethoxymethylhydantoin are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1669–1674, December, 1981.