Hydrolytic treatments

In this context, some experimental results relevant to these open questions of enzymatic degradation will be presented and will be discussed from the viewpoint of cellulose chemistry, together with a summary of our recent work on thermohydrolysis and acid hydrolysis of cellulose, performed in connection with research on cellulose powder manufacture (7). After a short survey of the experimental techniques applied, this contribution will be centered on three problems (1) the interaction of chain degradation and cross-linking in thermal and thermo-hydrolytic treatments of cellulose, (2) the influence of mechanical strain... 

Acid hydrolysis of these samples led to the results to be expected, i.e., a lowering of LODP and residue value by NH3 pretreatment and mercerization as well as by mechanical disintegration prior to the hydrolytic treatment (Table XII). With regard to residue value, an NH3 pretreatment again proved to be more efficient in enhancing accessibility than a mercerization, while the rate constant of chain-length degradation was increased somewhat more by mercerization. 

Breaking of complex structures Production of energy products or simple chemicals for example, lignin can be used for the synthesis of phenolic compounds upon hydrolytic treatment... 

Isolation and characterization of lignin structures Hydrolysis and separation. Mild hydrolysis has previously been used for the structural analysis of both softwood and hardwood lignins (10 -14). About 20% of the lignin was liberated from spruce wood and 40% of the lignin from beech wood by percolation of finely ground wood meal with water at 100 °C for several weeks (72). Such a mild hydrolytic treatment can be expected to lead to the rupture of only... 

Disaccharides of the hexuronic acid-hexosamine type constitute the fundamental repeating unit of many mucopolysaccharides, from which they are derived by hydrolytic degradation. Further hydrolytic treatment results generally in destruction of the uronic acid moiety of the disaccharide. Structural studies have been made on the disaccharides from hyaluronic acid (hyalobiouronic acid), chondroitinsulfate (chondrosine), and heparin (heparosine). 

Glucan was not significantly affected by the hydrolytic treatment, and the maximal glucan solubilization was only 11% for the severest conditions. Torget et al.(11) also reported a low solubilization of glucan when CS is relatively low. 

To satisfy the yields of aromatic aldehydes obtained (Table I), rates ki and must be considerably greater than the heterolysis rate, 3. This seems reasonable because equilibration of V and VII when aldehyde is removed should occur readily in the aromatic series where Ri can offer substantial resonance stabilization to the transition state, VI, by enhancing the cationic character of the carbonyl carbon. In Briner s early work (1,2) on the hydrolysis of stilbene and isoeugenol ozonides, advantage was not taken of these equilibria and rate differences. As a consequence almost half of the final cleavage products after extensive hydrolytic treatment without aldehyde removal were carboxylic acids, IX. 

Hydrolytic treatments can serve not only as a PET degradation method, but may simultaneously enable the separation of hydrolysable and non-hydro-lysable polymers present in the plastic waste stream. Thus, Saleh and Wellman64 have proposed the separation of PET and polyolefin mixtures by treatment with water from about 200 °C up to the critical temperature of water under autogenous pressure. The resulting liquid phase contains the hydrolysis products, TPA and ethylene glycol, whereas the solid phase is formed by the non-reacted polyolefins. 

Evidence that the reaction of the diol ester 5 with antimony pen-tachloride genuinely involves a neighboring-group reaction is provided by the stereospecificity of this reaction with esters of cyclic diols. trans -l,2-Cyclopentanediol diacetate (14) and Irons-1,2-cyclo-hexanediol diacetate (17) react " with antimony pentachloride to give the cis-acetoxonium salts 15 and 18, whereas the cis-diol esters (16 and 19) merely give difficultly soluble adducts from which unchanged starting material can be recovered after hydrolytic treatment. 

Perchlorocycloheptatriene, obtained by hydrolytic treatment of perchloro-tropylium heptachlorodialuminate isomerizes to perchlorotoluene by heating just below the melting point of the latter (about I90°C) (West and Kusada 1968). 

The reduction of perchlorofluorene with an excess of triphenylphosphine, followed by hydrolytic treatment, gives 9//,9//-octachlorofluorene (Camps, 1979). This reduction is interpreted as in (52). However, the postulated intermediate carbene, perchlorofluorenylidene, because of resonance stabilization, would rather react with triphenylphosphine to give the Wittig compound [66] than abstract a hydrogen atom (53). Accordingly, when the... 

Chlorine bridging is attributed to significant nucleophilicity of the AlCl4. Accordingly, if the counterion is SbClg (from SbClj), hydrolytic treatment affords ketones instead of chlorocarbons (p. 368). 

Since in PPDM- both p-positions are sterically blocked, its reaction with AICI3 in SO2CI2, although giving the corresponding carbenium ion, nevertheless on hydrolytic treatment affords only the normal chiorocarbon, perchloro-p,p -diphenyldiphenylmethane, and some perchloro-p,p -diphenyl-... 

Chlorination of perchlorotriphenylmethyl radical. PTM-, like some PDM radicals described on p. 355, reacts with a solution of AICI3 in SOjCl at room temperature to give ion PTM" (Ballester et al., 1982a). By hydrolytic treatment, the resulting solution affords perchloro-3-(diphenylmethylen)-cyclohexa-1,4-diene (PTM—Cl), the process probably taking place according to the mechanism (153), by analogy with the reaction of PDM- (130). 

Treatment of PTM—Cl with AICI3 in CH2CI2, in the absence of CI2, gives the carbenium ion salt. After hydrolytic treatment the Cl—PTM recovered contains an insignificant proportion of PTM- (155). 

PDA- reacts with chlorine in CCI4 in the dark giving, after hydrolytic treatment, the quinonoid compound [134] (22%) and PDA—H (73%) (Olivella, 1973). This conversion is interpreted in (195). The attack on a p-position, giving [134], is attributed to both steric shielding of the nitrogen and significant spin delocalization. 

PDNO- reacts with oleum at room temperature, giving a deep-blue solution, which, after hydrolytic treatment, yields the quinonimine 0= C CU NCgClj [137] (56%) and the amine (C6Cl5)2NH [138] (5%), PDNO-(26%) being recovered . The postulated reaction pathway involves ... 

It has been found that (i) the hydroxylamine [136], under the same conditions, gives a deep-blue solution (with ultraviolet-visible spectrum almost coincident with that of the solution from radical PDNO ), which after hydrolytic treatment affords the quinonimine [137] (84%), the diphenyl-amine [138] (12%) and PDNO- (4%) (ii) the oxammonium ion [140] can be... 

Another Bristol-Meyers Squibb process represents an enzymatic route for the production of side-chain precursors of Paclitaxel (33, Scheme 10) [69]. Racemic czs-azetidinone acetate (rac-31) is subjected to the hydrolytic treatment of Pseudomonas cepacia lipase (PCL), which is used in its immobilized form on polypropylene beads. Thus, (3R,4S)-acetate 31 can be obtained in high ee as well as the remaining alcohol 32. The process takes place in 150 1 reactors where 1.2 kg mc-31/batch can be resolved with a hydrolysis rate of 0.12 g/lh. Lowering the reaction temperature to 5 °C after full conversion causes (3R,4S)-31 subsequently to crystallize. Due to the immobilization, the enzyme can be reused for at least ten cycles without any loss of activity, productivity, or optical purity of the product. Paclitaxel is finally accessible by further chemical steps. 

The aim of this research was to create novel composites for bulk applications using cellulose as reinforcement. We intented to improve properties of polymer composites reinforced with cellulose by pretreating fibers with maleic anhydride modified polypropylene (MAPP). The effect of hydrolytical treatment of cellulose on the dispersibility of fibers in polymers was also investigated. Novel materials based on bacteria-produced polyesters and cellulose were manufactured and their properties evaluated. 

An important feature of the cellulose-polymer composites is the degree of dispersion of the fibers in the matrix and the overall homogeneity of the composite structure. Prehydrolytic treatment caused a highly significant improvement in this respect. This has to do primarily with the reduction of particle size of cellulose during hydrolysis. Figure 5 illustrates that the average size of the cellulose content is considerably reduced by 2 hours of hydrolytic treatment with formic acid in gas phase. Processability, measured by melt viscosity, is dramatically improved by hydrolysis. 

HPLC determination Acid and/or enzyme treatments simiiar to those applied in thiamin analysis are normally required for the transformation of FMN and FAD to riboflavin. A few methods avoid this hydrolytic treatment, proposing direct dilution of the sample in water or acetate buffer... 

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