Esterification of Hemicelluloses from Poplar Chips in Homogenous Solution of N,N- Dimethylformamide/Lithium Chloride

Abstract

Hemicelluloses, extracted from the delignified poplar chips with 8.0% NaOH-1.0% Na₂B₄O₇-10H₂O, were esterified with various acyl chlorides in the homogeneous N,N-dimethylformamide/lithium chloride system. Comparative reactions were performed with different molar ratios of acyl chloride/anhydroxylose, different concentrations of triethylamine, various reaction times, and reaction temperatures between 45°C and 75°C. The degree of substitution was controlled between 0.32 and 1.51. Under optimum conditions (sample 8, molar ratio 3:1, TEA% 280), over 75% of the hydroxyl groups in native hemicelluloses were stearoylated. The preparations were characterized by FT-IR and GPC techniques as well as their solubilities in various organic solvents. The molecular weight measurements showed minimal degradation of the hemicelluloses during the rapid reactions at 45-75° C for 30-45 min.     

Succinoylation of wheat straw hemicelluloses in N,N‐dimethylformamide/lithium chloride systems

The chemical modification of native wheat straw hemicelluloses with succinic anhydride using N,N‐dimethylformamide/lithium chloride system as solvent and pyridine and/or 4‐dimethyaminopyridine as catalyst has been examined. In particular, the progress of the succinoylation reaction is studied as a function of the molar ratio of succinic anhydride/anhydroxylose unit in native hemicelluloses from 1:1 to 5:1, DMAP concentration 0.025–0.20 g, reaction temperature 40–140 °C, and reaction time 2–12 h with succinic anhydride. The degree of substitution of succinylated hemicelluloses ranges between 0.4 and 1.5 depending on the experimental conditions. FTIR and ¹H NMR spectroscopic characterization of the esterified polymers indicates a monoester substitution. The thermal stability of the esterified polymer decreases slightly upon chemical modification, but no significant further decrease in thermal stability is observed for DS ≥ 0.7. © 2001 Society of Chemical Industry     

Thermal softening and melting of esterified wood prepared in an N2O4–DMF cellulose solvent medium

The thermal softening and melting of a series of esterified wood samples, whose preparation has previously been described,⁴ have been studied by measuring the deformation of the samples under constant load at a constant heating rate. The introduction of acyl groups into wood including part of the original crystal structure in cellulose makes the modified wood meal conspicuously thermoplastic. While untreated dry wood shows a thermal softening point (T_s) of ca. 260°C, esterified wood meal samples with acyl groups larger than caproyl have a T_s of around 100°C or less, and appeared to melt over the temperature range of 220° to 250°C. In this case, the melting occurs even with wood meal samples esterified with appropriate acid chlorides in an N₂O₄–DMF–pyridine medium only for 30 min at room temperature. This might be the first finding that wood meal is converted, as a whole, into a thermoplastic material which can melt without any accompanying detectable degradation.     

Acetylation of sugarcane bagasse hemicelluloses under mild reaction conditions by using NBS as a catalyst

Sugarcane bagasse hemicelluloses were partially acetylated with acetic anhydride using N‐bromosuccinimide (NBS) as a catalyst under mild conditions in an almost solvent‐free system. The overall yield and degree of substitution (DS) were varied from 66.2 and 83.5% and between 0.27 and 1.15, respectively, by changing the reaction temperature and duration. It was found that the yield and DS increased with reaction temperature from 18 to 80°C and reaction time between 0.5 and 5.0 h. The results showed that treatment of the native hemicelluloses with acetic anhydride using NBS as a catalyst conveniently provided the corresponding biopolymer esters. The products were characterized by FTIR, ¹³C‐NMR spectroscopy, and thermal analysis. The new biopolymer acetates were thermally stable to over 200°C but underwent significant and rapid thermal degradation when heated above the onset of thermal degradation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 53–61, 2004     

Corrosion inhibition by N‐(alkyloxycarbonylmethyl)‐N‐triethanol ammonium chloride with respect to the surface and thermodynamic properties

N‐[(octyloxycarbonylmethyl)‐ N‐triethanol ammonium chloride] (C₈ ), N ‐[(dodecyl‐oxycarbonylmethyl)‐ N‐triethanol ammonium chloride] (C₁₂ ) and N ‐[(hexadecyloxycarbonylmethyl)‐N ‐triethanol ammonium chloride] (C₁₆ ) were synthesized. Surface tension was measured in aqueous solution for different concentrations at 28, 38 and 48°C. Various surface properties of the synthesized surfactants were evaluated, particularly critical micelle concentration (CMC), efficiency (Π_CMC) as well as maximum surface excess (Γ_max) and minimum surface area (A_min). Micellization and adsorption in both liquid/air and liquid/solid interfaces thermodynamics were investigated. These products have pronounced surface activity and satisfactory corrosion inhibition of C‐steel in hydrochloric acid at 28, 38 and 48°C. © 1999 Society of Chemical Industry     

Thermal characterization of some products obtained by chemically modified poly(vinyl chloride) with phenol

The chemical modification of poly(vinyl chloride) (PVC) in reaction with phenol, in the absence of a catalyst and at temperatures within the range of 60°C and the boiling temperature of phenol (180°C), led to the reaction products with the general structure of a vinyl chloride–vinyl phenol copolymer. The synthesized polyphenols were thermally characterized using the following experimental techniques: thermo–optical analysis (TOA), thermogravimetry (TG), derivative thermogravimetry (DTG), and pyrolysis in combination with gas chromatography (P–GC). The PVC samples modified with phenol show a thermal stability lower than the original PVC sample. The glass transition temperatures (T_gs) increase with increased degree of chlorine substitution. The main pyrolysis products of the modified PVC samples are hydrocarbons with low boiling points (C₁–C₄), benzene, toluene, naphthalene, indan, and phenol. The semiquantitative estimation of the pyrolysis products of the synthesized samples led to the conclusion that the following structural element types can be present, statistically distributed along the chain: vinyl chloride and vinyl phenol units, acetylenic and ethylenic units, and indan type structures. © 1995 John Wiley & Sons, Inc.     

Preparation and characterization of a novel antibacterial acrylate polymer composite modified with capsaicin

A novel antibacterial acrylate polymer composite modified with capsaicin was successfully synthesized by a two-step reaction. Capsaicin and acryloyl chloride were firstly esterified, and then applied to solution polymerization with acrylate monomers and styrene. The yield of the esterified products was about 85.3%. The polymer was characterized by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), contact angle (CA) and antibacterial ring tests. The number-average molecular weight (M_n) of the polymer was 27214, based on the capsaicin-acrylate dosage of 6.5 wt%. The TGA revealed a stable thermal property. The contact angles of the polymers films on tinplate increased from 77.5° to 86.2° with the increasing amount of capsaicin-acrylate. The antibacterial tests demonstrated excellent antimicrobial capability of the polymers.     

Etherification of hemicelluloses from sugarcane bagasse

Conditions for the preparation of etherified hemicelluloses from sugarcane bagasse with 2, 3‐epoxypropyltrimethylammonium chloride (ETA) using sodium hydroxide as a catalyst in aqueous solution were studied comparatively. The extent of the etherification was measured by yield percentage and degree of substitution. The effects of reaction time of 3–7 h, reaction temperature of 50–80°C, temperature of alkaline activation of 30–60°C, and time of alkaline activation of 0–60 min on the reaction yield and degree of substitution were investigated in detail. The overall yield and degree of substitution were varied from 35.2 to 41.9% and from 0.14 to 0.33, respectively, by changing the reaction temperature and duration as well as time and temperature of alkaline activation. The new materials were characterized by FT‐IR and 13C NMR spectroscopy, thermal analysis as well as GPC. It was found that the thermal stability of the hemicellulosic ethers decreased after chemical modification, and the molecular weights of the etherified hemicelluloses were lower than those of the native hemicelluloses. ¹³C NMR spectra gave the evidence for etherification reaction and the quaternization of hemicelluloses occurred mainly at C‐3 position. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Friedel–craft N-alkylation and N-acylation of acrylamide: A novel approach for synthesis of alkylacrylamides

N-Alkylacrylamides and N-acylacrylamides were synthesized by a novel synthetic approach, namely, the Friedel–Craft reaction of acrylamide with alkyl chloride and acyl chloride, respectively. The reactions took place smoothly at room temperature and the time required for the reactions was very short. The monomers so synthesized were characterized by elemental analyses, IR, and ¹H-NMR spectroscopy. Characterization data are in agreement with the proposed structures of the products. Thus, a convenient method for the synthesis of N-alkylacrylamides was developed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1845–1850, 1999     

Succinoylation of wheat straw hemicelluloses with a low degree of substitution in aqueous systems

The reaction of wheat straw hemicelluloses with succinic anhydride in aqueous alkaline systems was studied. The products showed a rather low degree of substitution, ranging from 0.017 to 0.21. The effects of reaction times of 0.5–16 h, temperatures of 25–45°C, and molar ratios of succinic anhydride to anhydroxylose units in hemicelluloses of 1:5–1:1 on the succinoylation yield and degree of substitution were examined. With the reaction kept within a pH range of 8.5–9.0, a temperature range of 25–28°C, a reaction duration of 1–2 h, and a 1:1 molar ratio of succinic anhydride to hemicelluloses were preferred. The structure of the resulting polymers was determined with Fourier transform infrared and ¹H‐ and ¹³C‐NMR spectroscopy, which indicated monoester substitution. The thermal stability of the esterified polymer increased with chemical modification. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 757–766, 2002     

Preparation and properties of fully esterified erythritol

Pure tetraesters of erythritol with C₁₀, C₁₂, C₁₄, C₁₆, C₁₈ saturated, and C_18:1 unsaturated (oleoyl) fatty acyl chains have been prepared for the first time and characterized using the acylating systems fatty acid/N,N′‐dicyclohexylcarbodiimide/4‐dimethylaminopyridine (DMAP), fatty acid anhydride/DMAP, fatty acyl chloride/pyridine, and fatty acyl chloride/boron trifluoride etherate. For the first three systems the yields were in the range of 80–90% while the fatty acyl chloride/pyridine system has the advantage of lower cost. The fatty acyl chloride/boron trifluoride etherate system gave lower (ca 70%) yields of the tetraesters. The tetraesters of erythritol may have applications analogues to those of triglycerides. In addition, new applications can be envisaged for these compounds, as a result of their differences in physical, chemical, and biochemical properties compared to triglycerides. Practical applications: The tetraesters of erythritol with saturated fatty acyl chains may have applications analogous to those of saturated triglycerides. However, tetraesters with unsaturated fatty acid chains may have greater prospects of having industrial uses after doing chemistry on the carbon–carbon double bonds.     

A novel,efficient procedure for acylation of cellulose under homogeneous solution conditions

Commercially available cellulose (Avicel PH101) was successfully acylated under homogeneous solution conditions by the following novel procedure: 2.0 g of cellulose and 5.0 g of LiCl were introduced into a glass reactor, magnetic stirring was started, the pressure was reduced to 2 mmHg, the temperature was raised to 110°C in 30 min, and the reactor was kept under these conditions for another 30 min. N,N‐Dimethylacetamide, 60 mL, was introduced, atmospheric pressure was restored, and the temperature was raised to 150°C in 30 min. The system was kept under these conditions for 1 h, then the temperature was decreased to 40°C; in 2 h a clear cellulose solution was obtained. Acid anhydride was added, and the solution was stirred at 60°C for additional 18 h. Acetates, propionates, butyrates, and acetate/butyrate mixed ester were prepared with excellent reproducibility of the degree of substitution, from 1 to 3. The degree of polymerization of cellulose is negligibly affected by these reaction conditions. The distribution of the acetyl moiety among the three OH groups of the anhydroglucose unit follows the order C₆ > C₂ > C₃. Features relevant to the industrial application of this novel procedure are discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1355–1360, 1999     

Studies on viscosity build‐up properties of sodium alcohol ether sulphates

Narrow and broad range distributed ethoxylates of linear C₁₂–C₁₄ alcohols were synthesised using a calcium‐based unconventional catalyst and NaOH, respectively. Their composition was determined by gas chromatography. Sulphates were synthesised in the traditional way by reaction of ethoxylates with sulphur trioxide in a film reactor and neutralised with sodium hydroxide. Products were characterized by the ethoxylate homologue distributions and acid value of the intermediate sulphuric acid derivatives. Viscosity build‐up properties of the narrow and broad range distributed ethoxylates‐based sodium alcohol ether sulphates were studied. Effects of ethoxylate homologue distribution were compared with those of average ethoxylation grade and sulphation degree. It was shown that the acid number of the obtained sulphates, ethoxylate homologue distribution, average polyaddition degree and sodium chloride content influenced remarkably the thickening ability of ethoxylates. Furthermore, it was found that the limited content of the longer ethoxylate chains in narrow range distributed alcohol ethoxylates is responsible for enhanced viscosity build‐up properties of their sodium sulphate derivatives. The following empirical relationship was obtained: log η = (2.99 ± 1.25) + (3.78 ± 0.86) × 10⁻²V − (1.48± 0.15)N_av − (2.69 ± 0.7) × 10⁻²A_N + (0303 ± 0.058) × C_surf + (0.832 ± 0.041) × C_NaCl where η is the viscosity in cP, V is the distribution coefficient, N_av is the average oxyethylation degree, A_N is the acid number of alcohol ether sulphuric acid and C_surf and C_NaCl are concentrations (wt%) of the studied surfactants and sodium chloride, respectively. © 1999 Society of Chemical Industry     

Synthesis and thermal decomposition of poly(dodecamethylene terephthalamide)

A kind of semiaromatic polyamide, poly(dodecamethylene terephthalamide) (PA12T) was synthesized via a polycondensation reaction of terephthalic acid and 1,12‐dodecanediamine. The structure of prepared PA12T was characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance (¹H‐NMR), and elemental analysis. The mechanical properties of PA12T were also studied. The thermal behavior of PA12T was determined by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. Pyrolysis products and thermal decomposition mechanism of PA12T were analyzed by pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS). Melting temperature (T_m), glass transition temperature (T_g), and decomposition temperature (T_d) of PA12T are 310°C, 144°C, and 429°C, respectively. The Py‐GC/MS results showed that the pyrolysis products were mainly composed of 32 kinds of compounds, such as benzonitrile, 1,4‐benzenedicarbonitrile, N‐methylbenzamide, N‐hexylbenzamide, and aromatic compounds. The major pyrolysis mechanisms were β‐CH hydrogen transfer process, main‐chain random scission, and hydrolytic decomposition. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

A study of thermal decomposition of alkanethiols in pressure reactor

The thermal decomposition of four alkanethiols was investigated in this paper. The test was processed in a pressure reactor at 200–400 °C. GC/MS and GC/SCD were used to detect the products of thermal decomposition. The result indicates that the alkane groups of alkanethiols have great influence on the thermal stability of alkanethiols. N-butylthiol, isobutylthiol and n-hexylthiol begin to pyrolyse at about 250 °C and more than 75% decomposes at 400 °C after being maintained for 4 h. However, tert-octylthiol can be broken down at lower temperature below 200 °C and almost 75% decomposes at 250 °C after 4 h. The main product of thermal decomposition is H₂S and a free radical reaction is used to explain the decomposition mechanism.     

Effects of fatty acid chain length and degree of unsaturation on the surface activities of monoacyl trehaloses

The surface properties of monoacyl trehaloses with different acyl chains were investigated at 30°C, 40°C, 50°C, and 60°C. Monoacyl trehaloses were enzymatically synthesized and purified with silica gel column chromatography and semi-preparative high-performance liquid chromatography (HPLC), and the purity of products was identified by mass spectrometry (MS) and nuclear magnetic resonance (NMR). The surface tension of monoacyl trehalose in pure water was measured using Douy ring method at different temperatures. The critical micelle concentrations (CMC), surface tension at the CMC, γ _CMC, and residual area per molecule, a, were estimated from the curves. The CMC value of unsaturated monoacyl trehalose was affected by both the degree of unsaturation and the acyl chain length, and the effect of chain length on the CMC value was much stronger than that of the unsaturation degree. However, there was no significant dependency of the γ _CMC value and a values on the chain length or the unsaturated degree.     

Fatty acid and product selectivities of potato tuber lipid acyl hydrolase in esterification reactions with glycerol in organic media

Fatty acid [FA; butanoic (C₄); octanoic (C₈); tetradecanoic (C₁₄); and cis-9,12-octadecadienoic (C_18:2) acids] reaction selectivity and the corresponding acyl profiles in differentially accumulating acylglycerol (AG) products (mono-, di-, and triacylglycerols; MAG, DAG, TAG, respectively) were evaluated for Celite™-immobilized potato tuber lipid acyl hydrolase (LAH)-mediated esterification reactions in isooctane at 35°C and water activity of 0.19. The ordinal pattern of FA selectivities was C₈>C₁₄>C_18:2>C₄, and the AG products accumulating were α-MAG>DAG>β-MAG>TAG. A dimensionless expression for fatty acid partitioning coefficient (FAPC) was contrived to represent the partitioning patterns of specific FA into specific AG pools on the basis of an equivalent extent of FA reaction. These FAPC values indicated that preferential partitioning of FA was as follows: C₄ was preferentially partitioned into TAG, DAG, and β-MAG; C₈ was preferentially partitioned into DAG; C₁₄ was preferentially partitioned into α,β-MAG; C_18:2 was preferentially partitioned into α,β-MAG and TAG. These findings infer that the tendency for LAH-mediated esterifications to accumulate MAG is based, in part, on a constraint in reactivity of α-MAG of ≥10 acyl carbon groups to serve as acceptors for further esterification events. The general approach taken in this study may assist in identifying the discrete steps in assembling structured glycerides where different biocatalysts exhibit the greatest degree or control of reaction selectivity.     

Pyrolysis of model compounds of the flame retardant poly(N-dimethylphosphonomethyl acrylamide)

An investigation of the thermal decomposition of N-dimethylphosphonomethyl amides has shown that the major volatile products for decomposition above 300°C are methanol, the methyl ester of the carboxylic acid, the nitrile, the carboxylic acid, the N-methyl amide, and the N,N-dimethyl amide. Also, benzoic acid was the only volatile product detected in the decomposition of α-benzamidomethylphosphonic acid. A mass balance for the decomposition of N-dimethylphosphonomethyl benzamide at 420°C showed methanol and methyl benzoate to be the major volatile products. Methanol and benzonitrile formation increased with an increase in temperature at a faster rate than the other volatile products. The reaction of amides and phosphonates was further studied using sealed tubes in a furnace. Reaction of N-methylbenzamide with dimethyl methylphosphonate at 307°C in a sealed tube produced methyl benzoate and N,N-dimethylbenzamide. N,N-dimethylbenzamide and dimethylmethylphosphonate were also shown to produce methyl benzoate at 310°C. After a 5-min period more methyl benzoate was produced in the N,N-dimethylbenzamide reaction than in the N-methylbenzamide reaction. Also, addition of ethanol to the N,N-dimethylbenzamide/dimethyl methylphosphonate reaction resulted in less ethyl benzoate methyl benzoate after heating at 310°C.     

Disecondary amine synthesis and its reaction kinetics with epoxy prepolymers

3,3′‐Diaminodiphenyl sulfone (3,3′‐DDS) was reacted with acetaldehyde in the presence of sodium triacetoxy borohydride via reductive amination to yield a 3,3′‐DDS based secondary diamine, N,N′‐diethyl‐3,3′‐diaminodiphenyl sulfone. Near IR analysis indicated that the 5060 cm^?1 peak for primary amine (? NH₂) in 3,3′‐DDS was absent in the reaction product spectrum. The ? NH₂ proton peak at δ 5.66 ppm shifted to δ 6.16 ppm in the product. Methyl and methylene protons of CH₃? CH₂? NH? Ph? group were observed at δ 3.01 and 1.12 ppm, respectively, in the product. The carbon NMR spectrum of the reaction product showed new peaks at δ 37.46 and 14.47 ppm that further confirmed secondary amine formation. The liquid chromatography coupled mass spectra peaks at 248–250 for 3,3′‐DDS and 304 for the reaction product further supported the formation of N,N′‐diethyl‐3,3′‐diaminodiphenyl sulfone. A blend of N,N′‐diethyl‐3,3′‐diaminodiphenyl sulfone with diglycidyl ether of bisphenol‐A (DGEBA) epoxy prepolymer started reacting at about 110–125°C surpassing an energy barrier of ～ 66 kJ/mol as determined via differential scanning calorimetry analysis. Reaction kinetics were characterized via near IR spectroscopy specific to the reaction between secondary amine and DGEBA epoxy prepolymer. The results confirmed >97% conversion at a cure protocol of 5 h at 80°C, 5 h at 100°C, 11 h at 125°C, and 6 h at 185°C. N,N′‐diethyl‐3,3′‐diaminodiphenyl sulfone‐DGEBA thermoplastics displayed tensile and flexural modulii of 3.08 and 2.86 GPa, respectively, and glass transition temperature (T_g) of 120.77°C. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Lipase-catalyzed monoesterification of 1-O-hexadecylglycerol in organic solvents

A simple method is presented to esterify 1-O-hexadecyl-rac-glycerol using lipases in different organic solvents. The following fatty acids were used: C_14∶0, C_16∶0, C_18∶0, C_18∶1, and C_18∶2. Monoesterification was achieved by using a limiting amount of the fatty acid. Both the 1-O-hexadecyl-3-O-acylglycerol and the 2-O-acylglycerol were obtained in a total yield of 75% and a ratio of 7∶1 in dichloromethane after 3 d. Chromatographic data for the monoesters, useful for the identification of the natural products, are given (gas-liquid chromatography, thin-layer chromatography, reverse-phase thin-layer chromatography). The structure was confirmed by a chemical synthesis of 1-O-hexadecyl-2-O-hexadecanoylglycerol. The 3-O-glyceride was also formed by acyl migration, as the minor component. The monoesters were separated by column chromatography and characterized by ¹H and ¹³C nuclear magnetic resonance spectra.