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The oxidation of pyridine can be achieved with a number of peracids including peracetic acid and perbenzoic acid. [3] Oxidation can also be effected by a modified Dakin reaction using a urea-hydrogen peroxide complex, [4] and sodium perborate [5] or, using methylrhenium trioxide (CH 3 ReO 3) as catalyst, with sodium percarbonate. [6]
The first reaction is the formation of the N-2,4-dinitrophenyl-pyridinium salt (2). This salt is typically isolated and purified by recrystallization. The formation of the DNP-pyridinium salt. Upon heating a primary amine with the N-2,4-dinitrophenyl-pyridinium salt (2), the addition of the amine leads to the opening of the pyridinium ring.
Nitroso compounds present in stool do not induce nitrosamine formation, because stool has neutral pH. [7] [8] Stomach acid catalyzes nitrosamine compound formation and is the main location of the reaction during digestion. [9] The formation process is inhibited when amine concentration is low (e.g. a low-protein diet or no fermented food).
Nitrosation is typically performed with nitrous acid, formed from acidification of a sodium nitrite solution. Nitrous acid is unstable, and high yields require a rapid reaction rate. NO + synthon transfer is catalyzed by a strong nucleophile, such as (in order of increasing efficacy) chloride, bromide, thiocyanate, or thiourea.
In esterifications and acylations, pyridine activates the carboxylic acid chlorides and anhydrides. Even more active in these reactions are the derivatives 4-dimethylaminopyridine (DMAP) and 4-(1-pyrrolidinyl) pyridine. Pyridine is also used as a base in some condensation reactions. [114] Elimination reaction with pyridine to form pyridinium
The unusual alkyl nitrite starting material of the Barton reaction is prepared by attack of an alcohol on a nitrosylium cation generated in situ by dehydration of doubly protonated nitrous acid. [6] This series of steps is mechanistically identical to the first half of the mechanism formation of the more well-known aryl and alkyl diazonium salts.
The Sarett oxidation is an organic reaction that oxidizes primary and secondary alcohols to aldehydes and ketones, respectively, using chromium trioxide and pyridine.Unlike the similar Jones oxidation, the Sarett oxidation will not further oxidize primary alcohols to their carboxylic acid form, neither will it affect carbon-carbon double bonds. [1]
The phrase ipso nitration was first used by Perrin and Skinner in 1971, in an investigation into chloroanisole nitration. [18] In one protocol, 4-chloro- n -butylbenzene is reacted with sodium nitrite in t -butanol in the presence of 0.5 mol% Pd 2 (dba) 3 , a biarylphosphine ligand and a phase-transfer catalyst to provide 4-nitro- n -butylbenzene.