Esterification with acid anhydrides

Citronellol undergoes the typical reactions of primary alcohols. Compared with geraniol, which contains one more double bond, citronellol is relatively stable. Citronellol is converted into citronellal by dehydrogenation or oxidation hydrogenation yields 3,7-dimethyloctan-l-ol. Citronellyl esters are easily prepared by esterification with acid anhydrides. 

Esterification with acid anhydrides (Section 15.8) Acid anhydrides react with alcohols to form esters in the same way that acyl chlorides do. 

Esterification with acid anhydrides is very widespread, especially for preparative use. Acetyl derivatives are prepared by reacting alcohols with acetic anhydride for identification purposes this method is mainly used with polyhydric alcohols (see p. 311) and with higher-molecular alcohols (sterols, etc.). The alcohol is heated in acetic anhydride, usually in the presence of anhydrous sodium acetate, or also in pyridine, chloroform, or benzene solutions. The isolation is carried out either by diluting the reaction... 

Acid-catalyzed esterification of nerol and geraniol with acid anhydrides produces the corresponding esters. The acetates and isobutyrates are also avaUable commercial products. U.S. production of neryl acetate [141-12-8] in 1993 was 18 t at a price of 11.56/kg and that of geranyl acetate [105-37-3] was 132 t at a price of 9.86/kg (67). 

Substitution as a preceding reaction. In addition to the well known determination of primary and secondary alcohols via esterification with acetic anhydride in pyridine at about 98° C, esterification is possible at room temperature in ethyl acetate with perchloric acid117 or 2,4-dinitrobenzenesulphonic acid118 as a catalyst. However, as tertiary alcohols preferably split off their hydroxy group, they can be adequately determined by OH-substitution with HBr in glacial acetic acid according to... 

Scandium triflate (Sc(OTf)3), which is commercially available, is a practical and useful Lewis acid catalyst for acylation of alcohols with acid anhydrides or the esterification of alcohols by carboxylic acids in the presence of... 

The various ways in which esters of cellulose and phosphorous adds can be synthesized are esterification cellulose with free acids alcoholysis, with cellulose, of the esters and amides of phosphoric adds and esterification with mixed anhydrides df phosphoric adds and carboxylic adds. 

Starches have been chemically modified to improve their solution and gelling characteristics for food applications. Common modifications involve the cross linking of the starch chains, formation of esters and ethers, and partial depolymerization. Chemical modifications that have been approved in the United States for food use, involve esterification with acetic anhydride, succinic anhydride, mixed acid anhydrides of acetic and adipic acids, and 1-octenylsuccinic anhydride to give low degrees of substitution (d.s.), such as 0.09 [31]. Phosphate starch esters have been prepared by reaction with phosphorus oxychloride, sodium trimetaphosphate, and sodium tripolyphosphate the maximum phosphate d.s. permitted in the US is 0.002. Starch ethers, approved for food use, have been prepared by reaction with propylene oxide to give hydroxypropyl derivatives [31]. 

The course of the acetylation of 6 was examined kinetically.684 The observed time-dependence of the total rate-constant was interpreted in the form of three independent, acetylation stages, for each of which the values of activation energies were determined the energy of the second stage685 is lower than those of the other two.688 The rate constants for all six dideoxy derivatives of l,6-anhydro-)8-D-hexopyran-oses during esterification with acetic anhydride in pyridine were estimated because of the known difference in the behavior of carboxylic acid anhydrides and the corresponding acid chlorides during esterification in pyridine, the reaction with acetyl chloride was also studied.408 The sequence of reactivities for acetic anhydride is... 

Acylation of Alcohols. Several 4-aminopyridines speed up esterification of hindered alcohols with acid anhydrides by as much as 10 000 fold of these, DMAP is the most commonly used but 4-pyrrolidinopyridine (PPY) and 4-tetramethylguanidinop3ridine are somewhat more effective. DMAP is usually employed in 0.05-0.2 mol equiv amounts. 

A series of castor oil-based ester derivatives were prepared by the esterification of castor oil with acid anhydrides such as phthalic, maleic and succinic anhydrides. The effect of different concentrations of castor oil and its esters on the growth activities of the sugar beet pathogens Rhizoctonia solani and Sclerotium rolfsii was studied by determining the percentage... 

Condensation of 37 with the JK-ring carboxylic acid 38 under the Yam-aguchi conditions provided ester 39 in high yield (Scheme 4). After selective removal of the triethylsilyl (TES) ether, the resultant alcohol was converted to the allylstannane by the standard procedure. DIBALH reduction of the ester followed by in situ esterification with chloroacetic anhydride/DMAP/pyridine delivered of-chloroacetoxy ether 40. Intramolecular cyclization of 40 with magnesium bromide etherate in acetonitrile afforded the desired product 41 as a single stereoisomer in 82% yield. RCM reaction of 41 using 18 pro-... 

The mechanism of anhydride cure is complex and controversial because of the possibility of several competing reactions. The imcatalyzed reaction of epoxy resins with acid anhydrides proceeds slowly even at 200°C both esterification and etherification occur. Secondary alcohols from the epoxy backbone react with the anhydride to give a half ester, which in turn reacts with an epoxy group to give the diester. A competing reaction is etherification of an epoxy with a secondary alcohol, either on the resin backbone or that formed during the esterification, resulting in a -hydroxy ether. It has been reported that etherification is a probable reaction since only 0.85 eqiuvalents of anhydrides are required to obtain optimiun cross-linked density and cured properties (103). 

Esterification can be carried out using conventional reactions with acid chloride or with acid anhydrides. The etherification of inulin can be done using alkylepoxides as reactant. Carbamoylation reactions using alkyl isocyanate can be performed, obtaining inulin carbamates. 

Yoshino et al. [146,147] esterified a fluorinated alkanol, such as IH, H, 9//-hexadecafluorononanol-l, with maleic anhydride in the presence of p-tolue-nesulfonic acid monohydrate. The resulting bis-maleate ester reacted with sodium hydrogen sulfite to yield the sodium salt of the fluoroalkyl-2-sulfosuccinate. Oxyethylene groups were introduced by reacting the corresponding fluorinated alcohols with ethylene carbonate prior to esterification with maleic anhydride [148]. 

Scheme 11 Esterification of alcohols with acid anhydrides.

The mechanisms of the Fischer esterification and the reactions of alcohols with acyl chlorides and acid anhydrides will be discussed m detail m Chapters 19 and 20 after some fundamental principles of carbonyl group reactivity have been developed For the present it is sufficient to point out that most of the reactions that convert alcohols to esters leave the C—O bond of the alcohol intact... 

Esterification with carboxylic acid anhydrides (Section 15 8) Car... 

---