Monomethyl-substituted amine

Carbamates all have the general structure of RO(CO)NHCH3. It turns out that only carbamates with a monomethyl-substituted amine group are biologically active. Although these compounds are not widely used any more, there are two carbamates, the structures of which we should be aware. 

Seven heterocyclic nitrogen pyridine derivatives which consist of a nitrogen atom substituted into a six-member aromatic ring are also discussed in this chapter. The pyridine derivatives include the nonsubstituted pyridine, three monomethyl-substituted pyridines, and two ethyl-substituted pyridine derivatives. Reduction of the aromatic pyridine ring with hydrogen yields the piperidine molecule which is a secondary amine that has a hydrogen atom attached to the nitrogen atom. The pyridine derivatives serve both as true solvents and as chemical intermediates for numerous chemical products. 

In order to clarify the different behavior of anion 2 and 3 (Scheme 4.10) toward DMC, various anions with different soft/hard character (aliphatic and aromatic amines, alcohoxydes, phenoxides, thiolates) were compared with regard to nucleophilic substitutions on DMC, using different reaction conditions. Results were in good agreement with the hard-soft acid-base (HSAB) theory. Accordingly, the high selectivity of monomethylation of CH2 acidic compounds and primary aromatic amines with DMC can be explained by two different subsequent reactions, which are due to the double electrophilic character of DMC. The first... 

This reaction takes place in a matter of seconds and produces significantly more fluorescence than the diacetylmonoxime fluorophors. Excess reagent is quickly hydrolyzed to form nonfluorescent water soluble products. Secondary, tertiary, and aromatic amines did not react with fluram to produce any measureable fluorescence. The reaction did not occur when ammonia and ammonium salts were tested for fluorescence. Mass spectrometry of an actual field sample confirmed that the substitution product is the fluorescent species that is shown above. Further mass spectra studies indicated that dimethyl-urea is not produced during this reaction. This was later confirmed by introducing known quantities of the urea and little or no fluorescence was noted. These tests indicate that Fluram does react with the primary amine intermediate on the adsorbent according to the above equation, and that monomethyl amine and other primary aliphatic amines would interfere. 

The nitroso substitution products of secondary amines, e.g. monomethyl aniline, CcHb—NH(CHs), are formed by a rearrangement of the nitrosamine which itself is formed by the direct action of nitrous acid on the secondary amine (p. 547). 

Such decarboxylations are occasionally of industrial importance for example, primary amines may be monomethylated by converting them by chloroacetic acid into JV-substituted glycines which can then be decarboxyl-ated 15 / -(methylamino)phenol (Metol) is prepared industrially in this way. 

Dimethylcarbonate (DMC) is an environmentally friendly substitute for dimethylsulfate (DMS) and methyl halides in methylation reactions. It is also a very selective reagent. The reactions of DMC with methylene-active compounds produce monomethylated derivatives with a selectivity not previously observed. The batchwise monomethylation of arylacetonitriles, arylacetoesters, aroxyacetonitriles, methyl aroxyacetates, ben larylsulfones and alkylarylsulfones with DMC achieve >99% selectivity at 180-220°C in the presence of K2CO3. Mono- -methylation of primary aromatic amines at 120-150 °C in the presence of Y- and X-type zeolites, achieved selectivities up to 97%. At high temperature (200°C) and in the presence of potassium carbonate as the catalyst, DMC splits benzylic and aliphatic ketones into two methyl esters in contrast, DMC converts ketone oximes bearing a methylene group to 3-methyl-4,5-disubstituted-4-oxazolin-2-ones. Dibenzylcarbonate... 

Schwenk and Block [23] also suggested the use of morpholine as an amine, which permits operations in ordinary laboratory equipment. The reaction appears to be quite general for aromatic monomethyl ketones. Substitutions such as nitro, amino, hydroxy, or second ace-toxy groups interfere with the standard reaction, probably because these functional groups are capable of reacting with sulfur, polysulfides, or other components of the reaction mixture. 

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