Dehydration, amides

Use of 1,3 cycloaHphatic diamines in polyamides may be similarly limited by internal amide dehydration of the conformationaHy labile cis isomers to form a tetrahydropyrimidine (38) rather than high molecular weight polyamide. 1,3-Cyclohexanediamine is, however, a component of Spandex polyureas Du Pont uses the hydrogenation product of y -phenylenediamine [108-45-2] (24) captively to produce Lycra (see Fibers, elastomeric). 

Both methods of nitrile synthesis—SN2 displacement by CN- on an alkyl halide and amide dehydration—are useful, but the synthesis from amides is more general because it is not limited by steric hindrance. 

Ferrini and Marxer65 have recently shown that vinylene carbonate reacts with primary amides, in the presence of polyphosphoric acid, to yield 2-substituted oxazole derivatives. Yields are low (2-34%), and phenoxy- and phenyl-acetamide, p-methylbenzamide, and salicylamide do not give oxazole derivatives. Although the reaction has been interpreted according to Scheme 3, the nucleophilic attack of a nitrile molecule (from the amide dehydration), with a nitrilium salt as intermediate (Scheme 4), cannot be excluded.06... 

The nitrile functional group is, formally, a dehydrated primary amide. (In fact, u little-used nitrile synthesis involves amide dehydration ... 

The mixture of the isomers of trimethyladipic acids is treated with ammonia, converted to amides, dehydrated to nitriles, and reduced to amines ... 

Although 3-fluorophthalonitrile 12 - precursor for a-substituted tetrafluorophthalo-cyanines [MPCT4] - is commercially available and can be also easily prepared either from dimethyl 3-fluorophthalate 10 using an amidation-dehydration procedure [12], or by nucleophilic substitution from 3-nitrophthalonitrile 13 upon its treatment with dry tetramethylammonium fluoride in N,N-dimethylacetamide (DMAA) [5], so far only Cu" [12] and Zn" [5] complexes (14a and 14b) were briefly reported (Scheme 3). 

Fatty amines are produced by h. of - fatty nitriles, which are derived from - fatty acid and ammonia via the amide. Dehydration of the amide is the first step to yield the nitrile, which is hydrogenated in the presence of a catalyst. Aside from Ni and Co, noble metals and iron are used as catalysts in batch processes with suspended catalyst and in continuous processes with a fixed-bed catalyst. 

The other primary fermentation products of glucose are equally valuable as raw materials for chemical production. Succinic acid can be converted through hydrogenation to butanediol, and then through dehydration to tetrahydrofuran. 3-Hydroxypropionic add (3HPA) has bifunctionaUty that allows for reduction of the add group to alcohol, esters, and amides, dehydration of the alcohol function to... 

Nitriles and Isocyanides via Amide Dehydration. Thionyl chloride dehydrates primary amides to form nitriles (eq 8) for example, 2-ethylhexanonitrile is produced in about 90% yield by heating with SOCI2 in benzene. Substituted benzonitriles are readily produced from benzamides. These reactions may also be catalyzed by DMF. A -Alkylformamides may be dehydrated to isocyanides. ... 

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