Amino hydrogen atoms

The strong dependence of the reaction rate on the catalyst concentration relative to control experiments in which the amino-hydrogen atoms of 7 were substituted by methyl groups demonstrate that hydrogen bonding represents the major interaction responsible for the observed accelerations. Diels-Alder reactions are also accelerated by hydrogen-bond donors. It was shown that a biphenylenediol 9 is able to catalyse [4 + 2]-cycloadditions of cyclopentadiene, 2,3-dimethylbutadiene and other simple dienes with various a,fi-unsaturated carbonyl compounds (Table 14)175. 

Replacement, of acetylenic hydrogen atom by bromine, 45, 86 of acyl chlorine atom by fluorine atom using hydrogen fluoride, 46, 3 of amino hydrogen atoms by thio-carbonyl group, 46, 19 of aromatic bromine atom by potassium /-butoxide, 46, 89 of a-chloro atom in ester using azide ion, 46, 47... 

Figure 5-16. The deuteration of a co-ordinated amino acid. Note that usually exchange of the amino hydrogen atoms also occurs.

Since primary alkylamines are binucleophilic reagents, both amino hydrogen atoms are lost in reactions with unsaturated compounds. However, it should be realized that these are rather strong bases catalyzing isomerization of perfluoroolefins. 

As aniline, toluidine, xylidine, etc., are primary amines if we substitute alkyl or aryl radicals for one or both of the remaining amino hydrogen atoms we shall obtain secondary and tertiary amines. Such products may be typified by the following in which the methyl and phenyl radicals are substituted for the amino hydrogen in aniline. 

Di-anilides.—Aniline also yields di-anilides in which both amino hydrogen atoms are replaced by acid groups, e.g., di-acetanilide, CeHs—N=(OC—0113)2. Anilides are also formed from the alkyl anilines of the secondary group but not of the tertiary. 

Derivatives.—Four classes of derivatives of phenyl hydrazine are known (i) Those containing hydrocarbon radicals in place of amino hydrogen atoms,... 

Primary and secondary amines possess replaceable amino hydrogen atoms. With acid chlorides (RCOCl) or anhydrides, (RCO)jO, they yield crystalline derivatives which are very useful in their separation and identification. Benzoyl derivatives are often preferred to acetyl derivatives because the former are less soluble and have higher melting points further, benzoyl chloride, unlike acetyl chloride, is not ea.sily hydrolyzed in water, and hence the acylation can be carried out in aqueous solutions. Tertiary amines do not react and therefore can be obtained unchanged. 

Results obtained from an X-ray analysis of ANI in a crystalline state39 pointed out a certain distortion of the ring, and an asymmetry of the amino hydrogen atoms (without Cs symmetry), which is no doubt due to the crystal effect. Otherwise, the C-N distance and amino group bond angles in the crystal structure are quite close to the MW and calculated results. 

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