Amount Of Acetic Anhydride Research Articles

Optimization of Preparation Process of Oxidized Potato Starch Acetate by Response Surface Methodology

The response surface methodology(RSM) was used to optimize the preparation conditions of oxidized potato starch acetate.On the basis of one-factor-at-a-time experiments,a 29-run Box-Behnken experimental design involving 4 variables at 3 levels was used for mathematical modeling of substitution degree(SD) with respect to NaClO amount,acetic anhydride amount,pH and reaction time.The optimal reaction conditions for improved SD were NaClO amount 1.805%,starch/acetic anhydride ratio 5:1(m/m),pH 8.06 and reaction time 1.5 h,resulting in an SD of 0.0975.

Effect of the basic process parameters during polymerization of tetrahydrofuran with perchloric acid

Polymerization of tetrahydrofuran in the presence of the perchloric acid—acetic anhydride catalytic system evolves reversibly in time and is subject to the strong effect of the temperature, where the yield and molecular weight of the oligomer decrease when the temperature increases. The molecular weight of the oligomer can be regulated by changing the amount of catalyst. It is most sensitive to a change in the amount of perchloric acid, which must be measured very precisely, while finer regulation can be performed by varying the amount of acetic anhydride.

Gelation behavior with acetylation of chitosan for membrane preparation

The aim of this work is to investigate the gelation behavior of chitosans which has various degree of acetylation (DA) of amino group to ensure the preparation of the designed membrane structure. The DA was controlled by the amount of acetic anhydride added to the solution of chitosan/acidified water/methanol mixture. The gelation behavior was evaluated by the gelation time and the quantity of syneresis. The mechanical strength of acetylated chitosan gels was also measured. The optimum condition for the formation of the membrane, i.e. chitosan concentration, acetic acid/ chitosan mass ratio, methanol/water mass ratio, and amount of acetic anhydride for acetylation, was determined. This composition gives low contractility, shorter gelation time, and high mechanical strength to the membrane and the gel. Useful information not only for a preparation of a membrane but also for an immobilized carrier or a chemical reaction system was obtained in this work.

REDOX REACTION IN THE CYCLIZATION-AROMATIZATION OF (R)-(+)-CITRONELLAL WITH FECL3/ACETIC ANHYDRID

Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Â The effects of temperature, time of reaction, and the reactants mole ratio on the cyclization-acetylation of (R)-(+)-citronellal with FeCl 3 /acetic anhydride were studied. Â Isopulegyl acetate (IPA) and neoisopulegyl acetate (NIPA) were obtained as the main products at room temperature (mole ratio of citronellal: acetic anhydride: FeCl 3 = 6:12:1). Both products are relatively fixed after the 30th minute. The average concentration of IPA at 30-180 minutes was 44.71%, while the average concentration of NIPA was 28.47%. Increasing temperature (80 o C) and the amount of acetic anhydride (mol ratio 2:6:1) gave p -cymene (17.53%) and citronellyl acetate (11.31%). Autoredoks reaction on the transformation of citronellal into p -cymene and citronellyl acetate was studied with the carbon oxidation number concept. Key words : (R )-(+)- citronellal, cyclization-aromatization, FeCl 3 , Â p -cymene, redox

Synthesis of cellulose acetate from cotton byproducts

Cotton burr and cottonseed hull are relatively inexpensive cotton byproducts. In an effort to derive greater value out of these natural renewable materials, we have succeeded in converting part of them into cellulose acetate without prior chemical breakdown or physical separation of cellulose, lignin, protein, and other components. The conventional approach of treating the raw materials with acetic acid, acetic anhydride, and sulfuric acid in a solvent yielded very little product. An alternative process that involved treating the materials with acetic anhydride and iodine proved to be more successful. No solvent was used in this alternative approach except during the sample workup. The process was optimized by varying the temperature and the amounts of acetic anhydride and iodine used. The best yields obtained thus far were about 15–24%, which corresponded to conversion of between 50% and 80% of the starting cellulose. Formation of the acetates and the degree of substitution were monitored via NMR spectroscopy.

PHASE SEPARATION OF POLY(AMIC ACID-CO-IMIDE) SOLUTION

Poly(amic acid-co-imide) (PA-I) is an intermediate for preparation of polyimide from polyamic acid (PAA). Phase separation does not appear for the solution until a certain imidization degree. The experimental results of a rotation viscometer and FT-IR analysis showed that the critical point of phase separation (CPPS) was related to the imidization methods (thermal or chemical imidization) and the backbone structures (flexible ODPA-ODA or semi-rigid PMDA-ODA). Phase separation time is shorted with the increase of the initial PAA concentration, acetic anhydride amount, or temperature. When phase separation occurs, the solution viscosity increases, while the imidization degree is almost constant as the initial PAA concentration rises. The greater the chain mobility, the higher the imidization degree at phase separation point. At CPPS, higher imidization degree and lower solution viscosity are obtained in the thermal imidization than in the chemical imidization; ODPA-ODA system exhibits higher imidization degree and better solubility than that of PMDA-ODA system.

The preparation and characterization of chitosan wound dressings with different degrees of acetylation

AbstractChitosan fibers have in recent years found applications in various fields such as antimicrobial textiles and wound dressings. In this study, chitosan fibers with different degrees of acetylation were prepared by controlling the ratio between the amount of acetic anhydride and the weight of the fibers during the acetylation process. The absorption and antimicrobial properties, as well as the dry and wet strength of nonwoven chitosan wound dressings with different degrees of acetylation were studied. Results showed that the partially acetylated chitosan wound dressing had a much higher absorption capacity than the original untreated chitosan samples, while there was a reduction in the wet strength and antimicrobial property for the partially acetylated chitosan nonwoven dressing. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Large‐scale Synthesis of Per‐O‐acetylated Saccharides and Their Sequential Transformation to Glycosyl Bromides and Thioglycosides

This work describes a large‐scale synthesis of per‐O‐acetylated mono‐ and disaccharides using a stoichiometric amount of acetic anhydride in the presence of LiClO4 under solvent‐free conditions. The peracetylated saccharides underwent subsequent anomeric bromination and thioglycosidation in one‐pot to yield synthetically valuable building blocks.

Preparation of water‐soluble chitosan

AbstractAn improved method of preparing water soluble chitosan was studied by N‐acetylation with acetic anhydride. Its merits were a simple processing technique, very short reaction time, little agent, high molecular weight of the product, and good water solubility. This article not only discusses the effect of several factors, such as the amount of reactants, concentration of hydrogen ions in the solution, and solvent system, on N‐acetylation but also some influential factors on the water solubility of N‐acetylated chitosan. Experiments showed that the amount of acetic anhydride was the most important factor affecting the N‐acetylation degree of the chitosan. The effect of the means of adding materials and the amount of solvent on the reaction could not be ignored. The solubility of half N‐acetylated chitosan was not changed with an increase in the molecular weight in water, and the water solubility decreased with increasing molecular weight in the alkaline region. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3497–3503, 2004

Preparation of sulfoacetate derivatives of cellulose by direct esterification

A new and efficient method for the preparation in one step of water-soluble cellulose acetate sulfate derivatives (CAS) is reported. Acetylation and sulfation were carried out simultaneously, using a mixture of acetic anhydride and sulfuric acid in glacial acetic acid. The reaction time and the amount of acetic anhydride were optimized and the method provided water-soluble esters, with a degree of acetylation in the range 1.6 and 2.4 and a degree of sulfation of 0.3. This method has been successfully applied to pure cellulose and to cellulose-enriched materials obtained from agricultural by-products. The product exhibited a high viscosity in aqueous solution suggesting interesting rheological properties.

A Convenient and Selective Method for Preparation of Enol Acetates from Ketones Using Montmorillonite KSF Clay.

The reaction of ketones with stoichiometric amounts of acetic anhydride and Montmorillonite KSF clay at room temperature afforded the corresponding enol acetates in excellent yields. It has also been observed that by performing the reactions under microwave irradiation the reaction time can be dramatically reduced.

Effect of the degree of acetylation of chitosan on its enzymatic hydrolysis with the preparation Celloviridin G20x

The degree of acetylation exerted only insignificant effects on the enzymatic hydrolysis of chitosan, while affecting the composition of the resulting hydrolysates and their water solubility. Chitosan with various degrees of acetylation was produced by reacetylation of the original chitosan (the solvents, methanol and 2% acetic acid, were present at a ratio of 54:51 v/v; the amount of acetic anhydride was in the range 0.1-2.0 mmol per 1 g chitosan). Hydrolysis by the enzymatic preparation Celloviridin G20x was performed at the enzyme to substrate ratio of 1:400 in sodium-acetate buffer, pH 5.2 (55 degrees C) for 1 h.

Non-catalytic photo-induced graft copolymerization of methyl methacrylate onto O-acetyl-chitin

O-Acetyl-chitin was prepared in a lithium chloride- N,N-dimethylacetamide (LiCl/DMAc) system with high yield. The degree of acetylation was controlled with the amount of acetic anhydride. The obtained O-acetyl-chitin swelled not only in polar organic solvents, such as N,N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO), but also in water. O-Acetyl-chitin powder was graft-copolymerized to methyl methacrylate without catalyst. Graft copolymerization was initiated by the photolysis of the O-acetyl-group and the polymerization in a Quartz tube proceeded easier than in a Pyrex tube. The addition of DMSO in the reaction system did not always accelerate the graft copolymerization. Effects of various factors such as monomer concentration, degree of substitution of the O-acetyl-group and polymer concentration were also investigated.

Synthesis of starch acetate: Statistical designed experiments to optimize the reaction conditions

The synthesis conditions for Durabond A corn starch acetate (SA) were varied by using statistical designed experiments with the aim to optimize the yield and solubility, and to minimize the color. The thirty experiments in the design vary the: (1) Percentage water in the starch (0, 3, 6); (2) catalyst concentration (0.25, 0.60, 0.95 wt%); (3) total amount of acetic anhydride (1.0, 1.25, 1.5 mol times the number of hydroxyl groups on the starch); (4) starch concentration (15, 25, 35 wt%); (5) reaction time (1, 2.5, or 4 h); and (6) reaction temperature (60, 80 or 100°C). The major factors controlling the acetyl value (AV), yield and the solubility are the reaction temperature (T) and the T squared. Some two factor interactions that effect the process are: (1) water percentage with T, (2) the reaction time with T, and (3) the catalyst concentration with starch concentration. The optimal conditions are: (1) a T range from 84°C to 92°C; (2) a sulfuric acid catalyst concentration of 0.25 wt% with respect to the starch concentration, (3) an acetic anhydride ratio of 1.0; (4) a 35 wt% starch concentration; (5) a 4 h reaction time, and (6) a percentage water in the starch of (0–6%). There is a strong correlation between the 10% and 20% SA solution solubility in acetone:water (96:4) with the AV. If the AV is > 55 then > 90% of the SA at a concentration of 10% is soluble in acetone:water (96:4).

Preparation of N-acetylchitooligosaccharides from lysozymic hydrolysates of partially N-acetylated chitosans

The conditions for preparing partially N-acetylated chitosans (PNACs) by reaction of chitosan with acetic anhydride in homogeneous solution were investigated. The following conditions are recommended: chitosan, 1%; acetic acid, 0.4%; methanol, 50%; at room temperature. About 80% of the acetic anhydride reacted with amino groups and the degree of N-acetylation (da) of PNACs was easily controlled by the amount of acetic anhydride. PNACs were hydrolysed by lysozyme at 37°C for 6 days and hydrolysates were analysed by HPLC. 2-Acetamido-2-deoxy- d-glucose and N-acetylchitooligosaccharides [(GlcNAc) n ( n = 2–4)] together with heterooligosaccharides composed of 2-acetamido-2-deoxy- d-glucose and 2-amino-2-deoxy- d-glucose were detected. The latter were N-acetylated by acetic anhydride, to yield (GlcNAc) n . N-Acetylation of the hydrolysates doubled the amount of total (GlcNAc) n and (GlcNAc) 3, and increased the amount of (GlcNAc) 4 ninefold. The amount of (GlcNAc) n after the hydrolysis and the N-acetylation increased with the increase of da of PNACs. The optimum da for the formation of oligomers was ca. 70%. The yields of (GlcNAc) n ( n = 2–5) after gel filtration chromatography were 16.3, 10.3, 18.0, and 1.7 mg, respectively, from the hydrolysates of 72% N-acetylated chitosan (100 mg). This procedure is useful for the production of (GlcNAc) 2, (GlcNAc) 3, and (GlcNAc) 4.

Product Distributions in the Liquid-phase Oxidation of Cyclohaxane over CoAPO-5.

CoAPO-5 has been found to be a potential catalyst for the one-step liquid-phase oxidation of cyclohexane to produce cyclohexanone and adipic acid (without any promoter being added and with no induction period). Effects of various reaction conditions, including catalyst loading (10–5–2.5 × 10–3 kg), concentration of cyclobexane (1.44–4.33 × 103 mol/m3), oxygen pressure (5–15 × 105 Pa), temperature of reaction (115–135°C) and amount of acetic anhydride (0–60 × 10–6 m3) on the conversion and selectivity of liquid-phase oxidation of cyclohexane using CoAPO-5 as catalyst have been investigated. The results reveal that the selectivity of adipic acid is higher at reaction conditions of higher cyclohexane concentration, higher reaction temperature (135°C) and higher oxygen pressure (15 × 105 Pa) before 4 hrs. Accumulated water in the reaction mixture will affect conversion and selectivity of reaction if its amount is large enough. Addition of acetic anhydride increases the rate of cyclohexane oxidation and the selectivity of cyclohexylacetate (from the esterification of cyclohexanol and acetic acid) and succinic acid but lowers the selectivity of adipic acid.

HIGH TENACITY AND HIGH MODULUS FIBERS FROM WHOLLY AROMATIC POLYIMIDES

Poly (amic-acids) were synthesized from pyromellitic dianhydride (PMDA) and aromatic diamines, of which the resultant C-N bonds are coaxial and oppositely directed (rigid diamines), using Nmethylpyrrolidone as polymerization solvent. Random copolymers composed of rigid diamine, PMDA and 3, 3′, 4, 4′-diphenylethertetracarboxylic dianhydride (DTDA) were also synthesized. These poly (amic-acids) were partially imidized by adding an appropriate amount of acetic anhydride (15_??_30 mole% based on amic-acid unit) into their solutions and then wet-spun, since it was found that partially imidized polymer solutions gave more transparent and void-free coagulated fibers than poly (amic-acid) solutions as polymerized. These fibers were then chemically converted to polyimides by immersing them in an acetic anhydride-pyridine mixture and heat-drawn.Relatively lower crystalline polyimides such as polypyromellitimides of aromatic diamines bearing chlorine substituent on the nuclei or random copolyimides had better drawability and gave fibers having higher tensile strength than higher crystalline polymers. For example, poly [2, 2′-dichloro-4, 4′-biphenylene/p-phenylene (70/30) pyromellitimide] gave a fiber having tenacity (T) 16.3g/d, elongation (E) 2.0% and initial modulus (Mi) 960g/d. Another random copolymer composed of benzidine/PMDA/DTDA (100/40/60) yielded a fiber with the following tensile properties: T 19.7g/d, E 1.7% and Mi 1310g/d.

Enzymic and immunochemical properties of lysozyme—V derivatives modified at lysine residues by guanidination, acetylation, succinylation or maleylation

Modification of the amino groups in lysozyme was carried out by guanidination, acetylation, succinylation or maleylation. The specificity of each reaction for amino groups was carefully determined and the enzymic and immunochemical properties of all derivatives studied. Reaction of lysozyme with 1-guanyl-3,5-dimethylpyrazole nitrate gave an electrophoretically homogeneous derivative in which five amino groups were guanidinated. No other amino acids were modified and the derivative exhibited no conformational changes and suffered no loss in enzymic activity, relative to native lysozyme. By acetylation of lysozyme with different amounts of acetic anhydride, two electrophoretically homogeneous derivatives were prepared. Both derivatives were acetylated at all seven amino groups, but one had seven and the other had all fifteen hydroxy amino acids esterified. Reaction of lysozyme with succinic or maleic anhydride resulted in electrophoretically heterogeneous preparations even when all amino groups were modified. There was also a non-uniform esterification of aliphatic hydroxy amino acids. The acetylated, succinylated, or maleylated derivatives showed small, but measurable conformational changes. The enzymic activity was completely eliminated upon acylation of four or more amino groups and this loss was attributed to changes in electrostatic interactions between the modified enzyme and the negatively charged bacterial cell wall. With antisera to lysozyme, the guanidinated derivative possessed full (100 per cent) antigenic reactivity, relative to lysozyme. The two acetylated preparations retained substantial, and comparable, antigenic reactivity with these antisera. In succinylated or maleylated derivatives, the electrophoretic heterogeneity was not accompanied by immunochemical heterogeneity. A considerable amount of cross-reactivity was retained, even when all amino groups were succinylated or maleylated. Partially or completely succinylated lysozymes were antigenic in rabbits and antibodies to the completely succinylated derivative exhibited (a) a specificity against lysozyme, (b) a specificity against antigenic regions containing succinyl groups and showing carrier specificity and (c) a haptenic specificity against succinyl groups attached to unrelated carrier proteins. From these findings it was concluded that retention of the charge of certain amino groups is essential for intact antigenic reactivity. Some amino groups (possibly four) and at least eight aliphatic hydroxyl groups are not located within antigenic sites of lysozyme. Furthermore, succinyl and maleyl groups are immunochemically distinct.

Catalytic acetylation of flavonoids

On catalytic acetylation in the presence of magnesium perchlorate, flavonoids do not react with the catalyst. The highest yield of product was found when using the smallest amount of acetic anhydride (1 · 10−1 mole per 1 · 10−3 mole of quercetin) and 3 · 10−4 mole of Anhydrone.

Fluorenylhydroxamic acids isomeric with the carcinogens N-fluoren-2-ylacetohydroxamic acid. Part I. Synthesis of N-fluoren-1-yl-, N-fluoren-3-yl-, and N-fluoren-4-ylacetohydroxamic acid

Three new fluorenylhydroxamic acids isomeric with the carcinogen N-fluoren-2-ylacetohydroxamic acid have been synthesized by partial catalytic reduction of the corresponding nitrofluorenes, prepared in turn by oxidation of the respective fluorenamines with peroxymaleic acid. A route to N([1-14C]fluoren-1-yl)acetamide and -acetohydroxamic acid by aromatization of the oxime of 3,4-dihydrofluoren-1 (2H)-one by the Semmler–Wolff rearrangement has been explored. Analysis of the products by t.l.c. indicated the imine as an intermediate when this oxime was rearranged in the presence of limited amounts of acetic anhydride.