Stereoelectronic effects in tertiary amine nitrosation: nitrosative cleavage vs. aryl ring nitration

Abstract

The nitrosation (acetic acid) of N-(4-chlorophenyl)pyrrolidine gives at least 30% N-(4-chloro-2-nitrophenyl)pyrrolidine while the corresponding aryldibenzylamihe gives no nitration and only nitrosative dealkylation at nitrogen. This difference in reaction site has been probed with jV-(4-chlorophenyl)diethylamine. This substance undergoes competitive ring nitration to jV-(4-chloro-2-nitrophenyl)diethylamine (50%) and nitrosative dealkylation to (4-chlorophenyl)ethylnitrosamine (50%). The former compound nitrosates further to give (4-chloro-2nitrophenyl)ethylnitrosamine. This substance denitrosates to give the corresponding secondary amine. The reactivity differences result from stereoelectronic factors controlling the amine nitrogen unshared pair delocalization into the aryl ring. This interpretation is supported by 13C NMR data and mechanistic arguments.

Nitrosamine Formation in the Desorber of Tertiary Alkanolamine-Based Carbon Dioxide Capture Systems

“…The amine radical cation is subsequently also converted to an iminium ion via base deprotonation, followed by rapid oxidation (Scheme , pathway B) or NO 2 -mediated H-abstraction on the α-C of the amine radical cation (Scheme , pathway C). ,, The common intermediate iminium ion reacts with nitrite to form nitrosamines in all three pathways. In acidic nitrite solutions, it was suggested that the iminium ion would hydrolyze to form a secondary amine prior to forming a nitrosamine. , However, this step may not be necessary under desorber conditions (basic pH and high temperature), because the iminium ion was shown to be the active intermediate responsible for nitrosamine formation from secondary amines DELA and MOR at pH 6–9 in the presence of formaldehyde . This is partially supported by our secondary amine analyses.…”

“…In acidic nitrite solutions, it was suggested that the iminium ion would hydrolyze to form a secondary amine prior to forming a nitrosamine. 32,39 However, this step may not be necessary under desorber conditions (basic pH and high temperature), because the iminium ion was shown to be the active intermediate responsible for nitrosamine formation from secondary amines DELA and MOR at pH 6−9 in the presence of formaldehyde. 40 This is partially supported by our secondary amine analyses.…”

Nitrosamines from tertiary amines and dinitrogen tetraoxide

“…Favourable conditions permitted the expectation of an intermediate formation of iminium nitrate and nitrite salts (hemiaminal nitrate and nitrite esters) [equations ( l F ( 4 ) ] and an equilibration between them maintained by the presence of dinitrogen tetraoxide [equation (9)]. Nitrosamine formation was then accounted for by a thermolysis of the hemiaminal nitrite ester as was previously proposed [equation (6)]. 4y5 Thermolysis of a hemiaminal nitrate ester to a nitramine was not observed.…”

Opportunities for greener alternatives in chemical formulations

“…Primary and tertiary amines do not usually form nitrosamines, unless they are contaminated with secondary amines. However, aryldialkylamines [94][95][96][97] and certain other tertiary amines 92,94,98 can react at significant rates.…”