Nitrosation of aromatic compounds
AssigneeThe Dow Chemical Company
InventorsWilliam E. Smith, Thomas W. McGee
Life of this patent
Estimating the term…
Abstract
Aromatic compounds in an acidic, aqueous solution can be economically nitrosated by treatment with the hydration products of oxides of nitrogen at a temperature in the range of -15.degree. C. to 10.degree. C. The oxides of nitrogen are generated as a gas from a separate solution or slurry by the reaction of an alkali metal nitrate with a strong mineral acid at a temperature in the range of 15.degree. C. to 35.degree. C. This method of nitrosation employs relatively inexpensive reagents, but can be carried on continuously and produces unexpectedly high yield of para-nitrosated product from a monosubstituted starting material.
Claims14
A method of preparing a nitrosating agent in an aqueous solution comprising the sequential steps of:
- (a) bringing together an alkali metal nitrite with a strong mineral acid in a first aqueous medium at a temperature in the range from about -15.degree. C. to about 35.degree. C.;
- (b) generating oxides of nitrogen in said first medium by maintaining or elevating the temperature of the medium to a range from about 15.degree. C. to about 35.degree. C. during or following the bringing together of said nitrite and acid, said oxides evolving into the atmosphere above the medium;
- and
- (c) removing said evolved oxides of nitrogen to a second acidic, aqueous solution, comprising an acid or mixture of acids selected from the group consisting of nitric acid, hydrochloric acid, sulfuric acid and acetic acid, maintained at a temperature in the range from about -15.degree. C. to about 10.degree. C. to produce the nitrosating agent in said solution.
A method of nitrosating a phenylic compound nitrosatable in a nuclear position with a nitrosating agent in solution comprising the sequential steps of:
- (a) bringing together an alkali metal nitrite with a strong mineral acid in a first aqueous medium at a temperature in the range from about -15.degree. C. to about 35.degree. C.;
- (b) generating oxides of nitrogen in said first medium by maintaining or elevating the temperature of the medium to a range from about 15.degree. C. to about 35.degree. C., said oxides evolving into the atmosphere above the medium;
- (c) removing said evolved oxides of nitrogen into a second acidic, aqueous solution maintained at a temperature in the range from about -15.degree. C. to about 10.degree. C.;
- and
- (d) bringing together said nitrosatable phenylic compound with said evolved oxides of nitrogen in the seond acidic, aqueous solution, comprising an acid or mixture of acids selected from the group consisting of nitric acid, hydrochloric acid, sulfuric acid and acetic acid, at a temperature in the range of from about -20.degree. C. to about 25.degree. C.
In the nitrosation of a nitrosatable phenylic compound with a nitrosating agent prepared by the addition of oxides of nitrogen to an aqueous solution comprising an acid or mixture of acids selected from the group consisting of nitric acid, hydrochloric acid and sulfuric acid at reactive conditions, the improvement wherein the oxides of nitrogen are generated at a temperature in the range from about 15.degree. C. to about 35.degree. C. from a separate solution in which an alkali metal nitrite is brought together with a strong mineral acid.
Dependencies are inferred from the claim text.