Secondary acetic anhydride

One disadvantage of using acetic anhydride is that with primary amines, traces of the diacctyl compound, RN(COCH3)2, niay be formed the chances of this secondary acetylation are, however, usually remote, and recrystallisation from an aqueous solvent will generally hydrolyse the diacetyl derivative rapidly back to the mono-acetyl compound. 

Acetyl derivatives. Primary and secondary amines are best acetylated with acetic anhydride ... 

The quinaldine is separated from any unreacted aniline and from the alkyl-anilines by treatment with acetic anhydride, basified with sodium carbonate and steam distilled. Only the primary and secondary amines are acetylated the acetylated amines are now much less volatile so that separation from the steam-volatile quinaldine (a tertiary amine) is facile. 

For this reason, acetic anhydride is generally preferred for the preparation of acetyl derivatives, but acetyl chloride, in view of its greater reactivity, is a better diagnostic reagent for primary and secondary amines. 

Cellulose triacetate is obtained by the esterification of cellulose (qv) with acetic anhydride (see Cellulose esters). Commercial triacetate is not quite the precise chemical entity depicted as (1) because acetylation does not quite reach the maximum 3.0 acetyl groups per glucose unit. Secondary cellulose acetate is obtained by hydrolysis of the triacetate to an average degree of substitution (DS) of 2.4 acetyl groups per glucose unit. There is no satisfactory commercial means to acetylate direcdy to the 2.4 acetyl level and obtain a secondary acetate that has the desired solubiUty needed for fiber preparation. 

Nitrile Intermediates. Most quaternary ammonium compounds are produced from fatty nitriles (qv), which are ia turn made from a natural fat or oil-derived fatty acid and ammonia (qv) (Fig. 2) (see Fats AND FATTY oils) (225). The nitriles are then reduced to the amines. A variety of reduciag agents maybe used (226). Catalytic hydrogenation over a metal catalyst is the method most often used on a commercial scale (227). Formation of secondary and tertiary amine side-products can be hindered by the addition of acetic anhydride (228) or excess ammonia (229). In some cases secondary amines are the desired products. 

By a suitable choice of activating reagents, primary and secondary alcohols can be selectively oxidi2ed to carbonyl compounds in good yields at room temperatures. Typical activating reagents are acetic anhydride, sulfur trioxide—pyridine, dicyclohexyl carbodiimide, and phosphoms pentoxide (40). 

Other Rea.ctlons, The anhydride of neopentanoic acid, neopentanoyl anhydride [1538-75-6] can be made by the reaction of neopentanoic acid with acetic anhydride (25). The reaction of neopentanoic acid with acetone using various catalysts, such as titanium dioxide (26) or 2irconium oxide (27), gives 3,3-dimethyl-2-butanone [75-97-8] commonly referred to as pinacolone. Other routes to pinacolone include the reaction of pivaloyl chloride [3282-30-2] with Grignard reagents (28) and the condensation of neopentanoic acid with acetic acid using a rare-earth oxide catalyst (29). Amides of neopentanoic acid can be prepared direcdy from the acid, from the acid chloride, or from esters, using primary or secondary amines. 

Cellulose acetate [9004-35-7] is the most important organic ester because of its broad appHcation in fibers and plastics it is prepared in multi-ton quantities with degrees of substitution (DS) ranging from that of hydrolyzed, water-soluble monoacetates to those of fully substituted triacetate (Table 1). Soluble cellulose acetate was first prepared in 1865 by heating cotton and acetic anhydride at 180°C (1). Using sulfuric acid as a catalyst permitted preparation at lower temperatures (2), and later, partial hydrolysis of the triacetate gave an acetone-soluble cellulose acetate (3). The solubiUty of partially hydrolyzed (secondary) cellulose acetate in less expensive and less toxic solvents such as acetone aided substantially in its subsequent commercial development. 

Catalytic hydrogenation of the nitrile function of cyanohydrins can give amines. As in the case of ordinary nitriles, catalytic reduction of cyanohydrins can yield a mixture of primary, secondary, and tertiary amines. Addition of acid or acetic anhydride to the reaction medium minimizes formation of secondary or tertiary amines through formation of the amine salt or acetamide derivative of the primary amine. 

Purification as their N-acetyl derivatives is satisfactory for primary, and to a limited extent secondary, amines. The base is refluxed with slightly more than one equivalent of acetic anhydride for half to one hour, cooled and poured into ice-cold water. The insoluble derivative is filtered off, dried, and recrystallised from water, ethanol, aqueous ethanol or benzene (CAUTION toxic ). The derivative can be hydrolysed to the parent amine by refluxing with 70% sulfuric acid for a half to one hour. The solution is cooled, poured onto ice, and made alkaline. The amine is steam distilled or extracted as above. Alkaline hydrolysis is very slow. 

Acetic anhydride has also been used as the acylating agent. The formation of thiiranes from thiocyanatohydrins having a tertiary hydroxy group is best achieved by p-toluenesulfonic acid-catalyzed acetylation.The analogous thiocyanatohydrins with a secondary hydroxyl and a tertiary thiocyanate function give a predominance of epoxide from thiocyanatohydrin acetates since the hydrolysis rate of the secondary acetate grouping becomes competitive with that of the tertiary thiocyanate. 

Acetanilide, Bromacetanilide.—Primary and secondary bases form acetyl derivatn-cs with acetic acid, acetyl chloiide, or acetic anhydride (see Reactions, pp. 76, 77)-... 

It is for this reason that the action of acetic anhydride is utilised, whic h only unites with tlie jirimary and secondary base. Diwiethylaniline is a weak base, which, like aniline, is neutral... 

For best results the commercial triethylamine (Matheson, b.p. 89-90°) should be purified to remove primary and secondary amines and water, either by distillation from acetic anhydride and then from barium oxide, or by reaction with phenyliso-cyanate.5 2 3 4... 

Even though formic anhydride is not a stable compound (see p. 714), amines can be formylated with the mixed anhydride of acetic and formic acids (HCOO-COMe) °°° or with a mixture of formic acid and acetic anhydride. Acetamides are not formed with these reagents. Secondary amines can be acylated in the presence of a primary amine by conversion to their salts and addition of 18-crown-6. ° The crown ether complexes the primary ammonium salt, preventing its acylation, while the secondary ammonium salts, which do not fit easily into the cavity, are free to be acylated. 

Bismuth(III) triflate is also a powerful acylation catalyst that catalyzes reactions with acetic anhydride and other less reactive anhydrides such as benzoic and pivalic anhydrides.113 Good results are achieved with tertiary and hindered secondary alcohols, as well as with alcohols containing acid- and base-sensitive functional groups. 

Derivatives of Methylene Violet 6 possessing long aliphatic chains are obtained by oxidative coupling of 3-acetoxyphenothiazine with a secondary amine in the presence of an oxidant such as iodine. The oxidative coupling of phenothiazine with amine is well known but in this case the reaction does not stop there but proceeds further at reflux temperatures to the phenothiazinone 74.9 Reduction of the latter dye and treatment with acetic anhydride yields the ballasted phenothiazine 6. Reaction of 75 with the dye chloroformate 70 yields the ballasted leuco dye developer 76. 

This also explains the use of pyridine in acetic anhydride as an acetylating reagent6 in the determination of primary or secondary alcohols and amines according to the following sequential reactions (with ROH as an example) ... 

Glacial acetic acid, pure or mixed with other solvents, is one of the most attractive solvents for the titration of amines. Commercial acetic acid containing not more than 1% of water (Karl Fischer titration check) can be used in normal practice for the highest accuracy, however, the water content must be lowered to about 0.01% by addition of acetic anhydride and standing for 24 h not more than the stoichiometric amount of acetic anhydride should be used in order to avoid possible reactions with active hydrogen-containing analyte components such as primary or secondary amines or alcohols. A similar procedure is followed in the preparation of perchloric acid titrant from the commercial... 

After cooling and dilution with methyl-Cellosolve (2-methoxyethanol), acetic anhydride is slowly added (in order to convert the secondary amine to amide) and the solution is cooled to room temperature. Finally, the resulting tertiary amine, representing the original unsaturate, is titrated with 0.5 N perchloric acid in methyl-Cellosolve, either visually (with thymol blue + xylene cyanol... 

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... 

Iridium-catalyzed transfer hydrogenation of aldehyde 73 in the presence of 1,1-dimethylallene promotes tert-prenylation [64] to form the secondary neopentyl alcohol 74. In this process, isopropanol serves as the hydrogen donor, and the isolated iridium complex prepared from [Ir(cod)Cl]2, allyl acetate, m-nitrobenzoic acid, and (S)-SEGPHOS is used as catalyst. Complete levels of catalyst-directed diastereoselectivity are observed. Exposure of neopentyl alcohol 74 to acetic anhydride followed by ozonolysis provides p-acetoxy aldehyde 75. Reductive coupling of aldehyde 75 with allyl acetate under transfer hydrogenation conditions results in the formation of homoallylic alcohol 76. As the stereochemistry of this addition is irrelevant, an achiral iridium complex derived from [Ir(cod)Cl]2, allyl acetate, m-nitrobenzoic acid, and BIPHEP was employed as catalyst (Scheme 5.9). 

---