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Compared to benzene, the rate of electrophilic substitution on pyridine is much slower, due to the higher electronegativity of the nitrogen atom. Additionally, the nitrogen in pyridine easily gets a positive charge either by protonation (from nitration or sulfonation) or Lewis acids (such as AlCl 3) used to catalyze the reaction. This makes the ...
In a letter to Angewandte Chemie, the German chemist Manfred Christl [14] pointed out not only that the alleged new chemistry was in fact 100-year-old Zincke chemistry but also that the proposed structure for the reaction product was not the 12 membered ring but the 6 membered pyridinium salt (structure 2).
Direct nitration of pyridine is sluggish. [89] [90] Pyridine derivatives wherein the nitrogen atom is screened sterically and/or electronically can be obtained by nitration with nitronium tetrafluoroborate (NO 2 BF 4). In this way, 3-nitropyridine can be obtained via the synthesis of 2,6-dibromopyridine followed by nitration and debromination ...
[1] This effect was described in 1935 by John W. Baker and W. S. Nathan. [2] [3] [4] They examined the chemical kinetics for the reaction of pyridine with benzyl bromide to form a pyridinium salt, and a series of benzyl bromides having different alkyl groups as substituents at the para position.
In the so-called Ter Meer reaction (1876) named after Edmund ter Meer, [14] the reactant is a 1,1-halonitroalkane: The reaction mechanism is proposed in which in the first slow step a proton is abstracted from nitroalkane 1 to a carbanion 2 followed by protonation to an aci-nitro 3 and finally nucleophilic displacement of chlorine based on an ...
In organic chemistry, nitration is a general class of chemical processes for the introduction of a nitro group (−NO 2) into an organic compound. The term also is applied incorrectly to the different process of forming nitrate esters ( −ONO 2 ) between alcohols and nitric acid (as occurs in the synthesis of nitroglycerin ).
The reduction of nitroaromatics is conducted on an industrial scale. [1] Many methods exist, such as: Catalytic hydrogenation using: Raney nickel [2] or palladium-on-carbon, [3] [4] [5] platinum(IV) oxide, or Urushibara nickel. [6] Iron in acidic media. [7] [8] [9] Sodium hydrosulfite [10] Sodium sulfide (or hydrogen sulfide and base ...
It is the conjugate acid of pyridine. Many related cations are known involving substituted pyridines, e.g. picolines, lutidines, collidines. They are prepared by treating pyridine with acids. [3] As pyridine is often used as an organic base in chemical reactions, pyridinium salts are produced in many acid-base reactions.