Non-pollutional process for producing aromatic nitro compounds w

Details Non-pollutional process for producing aromatic nitro compounds w Non-pollutional process for producing aromatic nitro compounds w

1992-03-27

1993-08-17

Cintins, Marianne M.

Organic compounds -- part of the class 532-570 series

Organic compounds

Polycyclo ring system containing anthracene configured ring...

552236, 552238, 564218, 568927, 568929, 568930, 568931, 568933, 568934, 568935, 568937, 568938, 568939, 568940, C07C 9718, C07C 9724

Patent

active

052370771

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to a process for producing aromatic nitro compounds. More particularly, the invention relates to a process for producing aromatic nitro compounds without using nitric acid or a nitric acid derivative as a direct nitrating agent.
2. Background Art
An aromatic nitro compound is an essential substance as the starting material for the production of a wide variety of typical organic industrial products such as pharmaceuticals, agricultural chemicals, plastics and explosives. For the industrial synthesis of these compounds, ever since the last century, there has been employed a method in which nitric acid is used either singly or in combination with other acid catalyst (sulfuric acid, phosphoric acid, etc.) as nitrating agent.
In this method, however, since a large amount of a highly concentrated acid is used, there are always involved the technical problems to be solved, which vary in nature according to the aromatic substrate to be nitrated, due to the disadvantage in nitration using nitric acid. Such problems include an exothermic reaction under the heterogeneous conditions in addition to danger in operation, treatment of a large amount of waste acid, use of a corrosion-resistant apparatus, difficulties in achieving continuous automation, tremendous heat generation and oxidation of the substrate.
Generally, the nitration reactions of aromatic compounds proceed with the nitronium ions (NO.sub.2.sup.+) as the reaction species which is generated in the course of the reaction shown by the following formula, so the single use of nitric acid can not provide a satisfactory nitration and it is therefore necessary to combinedly use a strong acid as auxiliary agent for converting nitric acid into acidinium ion (H.sub.2 NO.sub.3.sup.+): O+NO.sub.2.sup.+
Concentrated sulfuric acid or fuming sulfuric acid is industrially used for this purpose, but great cost is required for recovery or treatment of the acid after completion of nitration, and also a large amount of water or an alkaline agent is necessitated for neutralization and washing of the product. Furthermore, since the reaction is carried out under a strongly acidic condition, side reactions involving the carbocation species or radical cation species generated competitively in the course of the reaction are unavoidable. Intermixing of the various water- or oil-soluble organic compounds produced through the side reactions into waste water is a serious problem that could not be overlooked from the standpoint of environmental pollution.
It has been desired to establish a process for effectively producing aromatic nitro compounds without using any inorganic acid, which is troublesome to handle, such as nitric acid, sulfuric acid, phosphoric acid, etc., and with minimized environmental pollution.


DISCLOSURE OF INVENTION

The present inventors have found that the nitrogen oxides, most typically nitrogen dioxide, exhibit a strong nitrating function in the presence of ozone. That is, the present inventors have found that an aromatic compound can be directly nitrated by introducing a gaseous nitrogen oxide and ozone-containing (ozonized) oxygen or air into a chemically stable organic solvent having been dissolved or suspended therein the aromatic compound and making the nitrogen oxide act to the aromatic compound, under a mild condition at a temperature around room temperature. The present invention was attained on the basis of this finding.
Thus, the present invention provides:
(1) a process for producing an aromatic nitro compound which comprises dissolving or suspending an aromatic compound in a halogenated organic solvent, and introducing into the resulting solution or suspension a nitrogen oxide and ozone-containing oxygen or air, thereby nitrating the aromatic compound; and
(2) a process set forth in (1) wherein the nitration is carried out in the presence of a solid phase carrier, a cation exchange resin or a Lewis acid.
The present invention will be described in detail below.
According to the process of

REFERENCES:
Suzuki, et al., Chemistry Letters, No. 5 (1991) pp. 817-818.

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