TOMARU Junichiro Nihon Kayaku Co.Ltd.Chemist Research chemist, 化学品研究所, 研究員
MAEDA Koichi Nissan Chemical Industries Ltd.Central Research Institute Chief Research, 中央研究所, 主任研究員
TAMURA Rui Ehime University Associate Department of General Professor Education, 教養部, 助教授 (60207256)
A novel non-acid methodology for the preparative nitration of aromatic compounds with the lower oxides of nitrogen using a combination of ozonized air and some third substance as the promoter has been developed. The reaction, referred to as the kyodai-nitration, is now subject to industrially based research as the promising pollution-free and energy-saving substitute for the century-old, yet currently ongoing commercial process based on the use of nitric acid-sulfuric acid.
Aromatic compounds sudjected to the present novel type of nitration include benzene and alkyl derivatives ; halogenobenzenes ; Aromatic carbonyl compounds, acetals, acylals and anthraguinones ; benzoic acid, its salts, ester, acid chloride, nitrile and amide ; nitrobenzene and alkyl derivatives ; anilides and phenolic esters ; pyridiue and alkyl derivatives ; naphthalene and derivatives ; benzyl cvanide and trifluoromethylbenzene.
For this novel type of aromatic nitration, we have proposed a mechanism in which the reaction proceeds a dual mode depending on the oxidation potential of aromatic substrate ; nitrogen dioxide reacts with ozone to give nitrogen trioxide, which oxidizes aromatic substrate to form cation radical as an intermediate to ring substitution. In the absence of an appropriate oxidizable substrate, nitorgen trioxide is trapped by another molecule of nitrogen dioxide to form dinitrogen pentaoxide, which is a powerful nitrating agent in the presence of acid catalyst.
Although in some respect complimentary to the existing methodology, the kyodai-nitration is highly promising to provide a solution to one of the nowadays problem which the chemical industry is facing.