Ammonia with anhydrides

Rea.ctlons, As with other tertiary alcohols, esterification with carboxyUc acids is difficult and esters are prepared with anhydrides (181), acid chlorides (182), or ketene (183). Carbamic esters may be prepared by treatment with an isocyanate (184) or with phosgene followed by ammonia or an amine (185). 

Solvents influence the hydrogenation of oximes in much the same way as they do hydrogenation of nitriles. Acidic solvents prevent the formation of secondary amines through salt formation with the initially formed primary amine. A variety of acids have been used for this purpose (66 ), but acids cannot always be used interchangeably (43). Primary amines can be trapped also as amides by use of an anhydride solvent (2,/5,57). Ammonia prevents secondary amine formation through competition of ammonia with the primary amine in reaction with the intermediate imine. Unless the ammonia is anhydrous hydrolysis reactions may also occur. 

The presence of a polar axis confers anisotropic activity to organic crystals (Curtin Paul, 1981 Desiraju, 1984b). Common polar (noncentrosymmetric) space groups adopted by organic crystals areP2i2i2i and P2i- While chiral crystals must have polar directions, polar crystals need not be chiral. Anisotropic reactivity is seen for instance in the reaction of ammonia with p-bromobenzoic anhydride, which crystallizes with a polar axis the polar axis directs the reaction, p-bromobenzoic anhydride is chiral as well as polar. Chirality of the crystalline anhydride has been exploited to resolve a racemic gaseous amine the chiral crystal preferentially reacts with one of the enantiomers of the amine. Thus when p-bromobenzoic anhydride crystals are exposed to vapours of racemic phenylethylamine, the resulting amide contains one of the enantiomers in excess. 

ID S is synthesized by the reaction of ammonia with maleic anhydride in water. The synthesis of EDDS and IDS is also in accordance with the 3rd Principle of Green Chemistry Design Less Hazardous Chemical Synthesis, although they are still not perfectly green as there still some hazardous components. This can be a difficult principle to achieve completely as many reactive chemicals in the chemist s toolbox are often hazardous. 

Lactamide has been prepared by the action of gaseous ammonia on ethyl lactate 3 and from lactic anhydride 4 and gaseous ammonia. It has been made also by the action of ammonia gas on lactide.5 The amide was obtained in excellent yields by treatment of the acetone condensation product of lactic acid with ammonia.6 Amides have been prepared by the reaction of liquid ammonia with esters at temperatures varying from — 330 to... 

The two free hydroxy groups are First protected with acetic anhydride. In a second step the acetyl group is reductively cleaved by a Birch reduction with lithium in liquid ammonia.19 Lithium dissolves in the ammonia with the formation of solvated electrons. Stepwise electron transfer to the aromatic species (a SET process) leads first to a radical anion, which stabilizes itself as benzylic radical 38 with loss of the oxygen substituent. A second SET process generates a benzylic anion, which is neutralized with ammonium chloride acting as a proton source (see Chapter 12). 

Acid Amides can be produced by acylating ammonia with esters, acid anhydrides, or the acids themselves (above 100 °C) an important product is formamide from methyl formate. Alternatively acid amides can be synthesized by reacting acid halides with ammonia. Catalytic hydrogenation converts the acid amides to primary amines. Ammonia and aldehydes or ketones are the basis for different stable products. With formaldehyde hexamethylenetetramine (urotropine) is obtained with acetaldehyde, ammono acetaldehyde with benzaldehyde, hydrobenzamide with ethylene and propylene oxides, aqueous ammonia reacts to form ethanol- or propanolamine. 

With Ammonia.—With ammonia the acid anhydrides form amides just as do the acid chlorides,... 

In the laboratory amides are prepared by the reaction of ammonia with acid chlorides or, when available, acid anhydrides (Secs. 20.8 and 20.10). In industry they are often made by heating the ammonium salts of carboxylic acids. 

Manufacture of many important amino intermediates used for dyes and other purposes is usually by conversion or replacement of a substituent. For example, as already mentioned, in substituted nitro compounds, the nitro groups may be reduced with iron/hydrochloric acid, hydrogen and catalyst, or zinc in aqueous alkali. Partial reductions can be brought about with sodium sulfide. Amino groups may be introduced by replacing halogens in the aromatic ring. Another approach to amination is by attack on a substituted aromatic compound with ammonia or amines. Thus, for example, direct amination of p-chloronitrobenzene (15a) in the presence of a copper catalyst affords p-nitroaniline (15b) in almost quantitative yield l,4-dichloro-2-nitrobenzene (16) is converted in a similar way to 4-chloro-2-nitroaniline (17). Reactions of ammonia with carboxylic acids or anhydrides are carried out on an industrial scale. 

If a way can be found to make it from ammonia, maleic anhydride, and 4-aminobenzoic acid, it may be relatively inexpensive and useful. It could be the biodegradable equivalent of nylon 6 and nylon 6,6. Chain extension with bisoxazolines or other reagents in the extruder may be needed to increase the molecular weight to obtain optimum physical properties. 

Formally a three-component reaction, the combination of a carboxylic acid anhydride and ammonia with 2-aminonicotinic acids yields pyrido[2,3-r/]pyrimidin-4(3//)-ones 67, the substituent in the 2-position originating from the anhydride.133... 

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