Chemical modification of wood. I use of trifluoroacetic anhydride in the esterification of wood by carboxylic acids

Abstract

Treatment of beech sawdust with a series of mono-and dicarboxylic acids in benzene solution at 25-30' in the presence of molar proportions of trifluoroacetic anhydride resulted in esterification of the cell wall components. The esterification is shown to be due in part to acylation by the carboxylic acid and in part to trifluoroacetylation. The latter caused discoloration of the wood due to slow hydrolytic release of trifluoroacetic acid on storage at room temperature. Similar esterification of sapwood lengths of Ponderosa pine resulted in surface modification only and was accompanied by a significant decrease in impact strength property.In the presence of increasing concentrations of trifluoroacetic acid liberated during reaction, the acylating power, rather than trifluoroacetylating power, of the acyl trifluoroacetates is enhanced. 7 8The application of this possible method of esterification of the cell wall components of (i) attempted esterification with halogenoalkylmonocarboxylic acids, in the hope of producing a measure of flame-retardant property in addition to dimensional stabilisation and (ii) attempted esterification with dicarboxylic acids to produce an ester-type cross-linkage between adjacent cellulose chains.By the latter method, with trifluoroacetic anhydride and dicarboxylic acid in a molar ratio of 2:1, cross-linkage would be expected to occur by acylation by a di-acylium ion. Thus :wood has been made on two different fronts, viz. :

Dimensional Stability and Mechanical Properties of Plantation Poplar Wood Esterified Using Acetic Anhydride

“…Prakash et al (2006) reported that esterification of wood with octanoyl chloride improved the dimensional stability and photostability of the wood. Although other esterification reagents may in theory produce favorable products, their difficult processing requirements restrict their commercialization (Arni et al 1961;Funakoshi et al 1979;Shiraishi et al 1979). Poplar (Populus ussuriensis) is one of the main fast-growing Chinese plantation wood species.…”

Thermal Properties and Thermal Degradation of Cellulose Tri-Stearate (CTs)

“…One of the potential disadvantages of the acylation of cellulose with acyl chlorides was the degradation of cellulose or cellulose esters for the existence of HCl produced in the reaction [3]. On the other hand, the synthesis of cellulose esters with trifluoroacetic anhydride (TFAA) [12] has many advantages, short reaction time, reagents saving, mild reaction conditions as well as easy separation of products. Hence, CTs was prepared in a heterogeneous system using TFAA as a promoter.…”

Long chain cellulose esters with very low DS obtained with non-acidic catalysts

“…However, under non-catalyzed conditions, their reactivity is extremely low towards cellulosic hydroxyl groups. The reported reactions of cellulose with FA make use of co-reagents to transform the carboxylic acids into more reactive entities: trifluoroacetic anhydride (TFAA; Arni et al 1961), tosyl chloride (Shimizu and Hayashi 1989), mesyl chloride (Talaba et al 1996) or dicyclohexylcarbodiimide and pyrrolidinopyridine (Samaranayake and Glasser 1993).…”