Acetylation treatment

The condensation of 2-nitrobenzenesulfonyl chlorides with 3-amino-2-chloropyridine in the presence of pyridine at 60 °C gave the corresponding sulfonamides, which were reacted with sodium hydride and iodomethane to give the N-methylated products. Catalytic hydrogenation of the N-methylated compounds followed by acetylation, treatment with sodium hydride in DMF, and reaction with arylalkyl chlorides or methanesulfonates resulted in the formation of novel benzo[/]pyrido[]3,2-r-][l,2,5]thiadiazepines <2005JME7363>. 

The carboxylic acid 61 was converted to its aldehyde counterpart which, upon condensation with m-terf-butyldimethylsilyloxyphenyl-magnesium bromide, gave the alcohol 62. Conversion of the alcohol to the acetamide 63 was effected by a one-pot tosylation/sodium azide displacement, followed by hydrogenation (H2/Pd(C)/Florisil) and acetylation. Treatment of 63 by thallium(III) trifluoroacetate (TTFA)... 

The relative stereochemistry of the substituents attached to the cyclopropane ring of presqualene alcohol received further confirmation by a synthesis of the triacetate (13), obtainable from (1) by ozonolysis, reduction, and acetylation. Treatment of 3-methyl-truns-hex-2-ene-l,6-diacetate (14) with ethyl diazoacetate in the presence of copper powder gave two isomers (15) and (16) whose stereochemistry was assigned by n.m.r. The triacetate derived from synthetic (15) by reduction and acetylation was identical in all respects with the triacetate (13) from natural presqualene alcohol. Presqualene alcohol has a c.d. curve similar to, but of opposite sign to, that of (li ,2i )-trans-chrysanthemyl alcohol (17). The mechanism for the stereospecific biosynthesis of squalene from farnesol via presqualene alcohol has received detailed comment. ... 

McCabe and Pfaff (1989) found tissue pretreatment to be beneficial for RNA probes but not for DNA probes. Both glycine and acetylation treatments decrease background levels. 

Various mono- and ollgo-saccharide derivatives of KDO have been subjected to methylation, reduction and acetylation treatment to afford compounds suitable for mass spectrometric analysis. Rules for fragmentation of the 3-deoxyoctltol derivatives were... 

Ichazo et al. [120] reported the mechanical properties of treated and untreated sisal fiber. Polyolefin composites were developed using 20% fiber loading. Acetic anhydride was used and acetylated treatment showed an improved tensile modulus by 30-40%. But the impact strength and elongation at break decreased because of the rigid interface between fiber and matrix [120]. 

Effect of fiber treatments Alkali treatment on OPFs significantly improved its interfacial shear strength in polyester matrix [14]. Alkali treatment washed out the outer skin, better exposing fiber to the polyester matrix, leading to proper interaction between their surfaces. In addition, the fine holes created on alkali treatment allowed the polyester to penetrate into the fiber bundles in a better way. Acetylation treatment to the fibers improved impact strength of OPF-polyester composites due to improved fiber wettability and resulting fewer void spaces [71]. The tensile stress of OPF-polyester composites increased slightly upon both acetylation and silane treatments on fibers and decreased upon titanate treatment [14]. The flexural modulus of OPF-PP composites also increased considerably upon acetylation treatment on fibers. Similarly the abrasion resistance of OPF-polyester composites was enhanced upon alkali treatment to fibers [13]. Treated fibers enhanced the adhesion resistance of polyester resin by 75-85%, while untreated fibers enhanced the abrasion resistance only by 50-60%. 

Effect of fiber treatments Acetylation treatment on fibers reduced the water absorption (at 100°C) of untreated OPF-polyester composites from 15.8% to 5.7%. Good interfacial contact between fiber and matrix and increased hydrophobicity caused by the treatment lead to reduced water absorption. 

De Rosa et al. [15] reported a decrease in the moisture content of okra bast fibers after alkalization, bleaching, acetylation treatments. They found the water absorption ability of okra fibers increased after mentioned treatments. 

The acetylation treatment decreases the hydrophilic nature of the plant fibers. During the acetylation treatment the hydroxyl groups in the cellulosic fiber are replaced with acetyl functional groups. The decrease in hydrophilicity results in lower moisture intake and stronger interfacial bonding [8]. De Rosa et al. [15] obtained lower water content in acetylated okra fibers compared to untreated ones. Hill and Khalil [72] reported that the acetylation treatment enhanced the bioresistance of coir and oil palm fiber-reinforced polyester composites. 

After acetylation, treatment of the adduct with potassium tert-butoxide causes elimination of benzenesulfinic acid and acetic acid to form an acetal having a triple bond or a conjugated double bond, depending on circumstances (eqs 5 and 6). ... 

Acetylation treatment Acetylation employs acetic anhydride and acetic acid and results in plasticization of the fiber cellulose (Eq. 9.2). This is also known as esterification. Acetylation is not usually done independently and is preceded by pretreatment with NaOH. Acetylation reduces the moisture absorption capacity of fibers [20]. 

Acetylation treatment of natural fibers is originally applied to wood cellulose to stabilize cell walls against moisture, improving dimensional stability and envirormiental degradation [73]. Therefore, acetylation may contribute toward decreasing the moisture absorption of natural fibers [37]. Plasticization of cellulose-based natural fiber can be introduced by this treatment, which is related to an esterification method. During the treatment of natural fibers with acetic anhydride, the hydroxyl groups... 

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