Hydrogen atoms amines

Fischer-Hepp rearrangement The nitros-amines of aromatic secondary amines when treated with hydrochloric acid give nuclear substituted nitrosoamines. Among the benzene derivatives, if the para position is free the -NO group displaces the hydrogen atom there in naphthalene derivatives it enters the 1-position ... 

The cyclic carbonate of benzoin (4,5-diphenyl-l,3-dioxol-2-one, prepared from benzoin and phosgene) blocks both hydrogen atoms of primary amines after dehydration acid stable, easily crystallizable Sheehan oxazolinones are formed, which are also called Ox derivatives. The amine is quantitatively deblocked by catalytic hydrogenation in the presence of 1 equiv. of aqueous acid (J.C Sheehan, 1972, 1973 M.J. Miller, 1983). An intelligent application to syntheses of acid labile -lactams is given in the previous section (p. 161). 

Nucleophilic Addition. Reagents with labile hydrogen atoms, such as alcohols, thiols, phenols, carboxyHc acids and amines, add to ketenes giving the corresponding carboxyHc acid derivatives (1) as shown ia Figure 1 (38). Not many are of practical importance, as there are better ways to such... 

The biochemical basis for the toxicity of mercury and mercury compounds results from its ability to form covalent bonds readily with sulfur. Prior to reaction with sulfur, however, the mercury must be metabolized to the divalent cation. When the sulfur is in the form of a sulfhydryl (— SH) group, divalent mercury replaces the hydrogen atom to form mercaptides, X—Hg— SR and Hg(SR)2, where X is an electronegative radical and R is protein (36). Sulfhydryl compounds are called mercaptans because of their ability to capture mercury. Even in low concentrations divalent mercury is capable of inactivating sulfhydryl enzymes and thus causes interference with cellular metaboHsm and function (31—34). Mercury also combines with other ligands of physiological importance such as phosphoryl, carboxyl, amide, and amine groups. It is unclear whether these latter interactions contribute to its toxicity (31,36). 

The alkylation desctibed in this article is the substitution of a hydrogen atom bonded to the carbon atom of a paraffin or aromatic ring by an alkyl group. The alkylations of nitrogen, oxygen, and sulfur are described in separate articles (see Amines Ethers). 

Rearrangement, Aliphatic amine oxides without an ahphatic hydrogen atom P to the nitrogen undergo Meisenheimer s rearrangement when heated to give trisubstituted hydroxylamines. 

Diarylamines are compounds that have two aromatic groups and one hydrogen atom attached to nitrogen. Diphenyl amine (DPA), or... 

MSC undergoes reactions with alcohols, amines, active methylene compounds (in the presence of bases), and aromatic hydrocarbons (in the presence of Friedel-Crafts catalysts) to replace, generally, a hydrogen atom by a methanesulfonyl group (382—401). 

Mannich reaction is the condensation between formaldehyde, ammonia, or a primary or secondary amine (preferably as the hydrochloride), and a compound containing at least one active hydrogen atom... 

Autocatalysis may arise when the nucleophilic atom of the reagent is bound to a hydrogen atom which is eventually eliminated during the reaction. This occurs with neutral reagents such as primary or secondary amines, thiols, and alcohols. If the displaced group (usually an anion) is a sufficiently weak base, the proton is effectively transferred to any basic reactant. Hence, the best known examples of autocatalysis involve chloro-A-heteroaromatic compounds as the substrates. 

Difficulties are often encountered in the formation of peptides from a-amino acids which lack an a-hydrogen atom, e.g. a-methylalanine, presumably because of steric hindrance. This problem is obviated by use of the oxazolone 35, an excellent reagent for the addition of a single a-methylalanyl residue to an amine or amino acid [Eq. (22)]... 

Ethoxy-3,4-pyridyne (46) is involved in the amination of 3- and 4-bromo-2-ethoxypyridine, and mixtures of aminoethoxypyridines of the same composition are formed in both reactions. Thus, from 4-bromo-2-ethoxypyridine only the 3-hydrogen atom, situated between the bromine and ethoxyl groups (and not the 5-hydrogen atom) is abstracted. Pyridyne 47 is an intermediate in the amination of 4- and 5-bromo-3-ethoxypyridine. In the last-mentioned substance, just as in 5- (or 3-)bromopyridine, only the 4-hydrogen atom, and not the 2-hydrogen atom, is abstracted. The amination of 3-bromo-6-ethoxypyridine proceeds via 6-ethoxy-3,4-pyridyne (48). again the 2,3-pyridyne derivative is not formed. 

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