Checked by J. D. Roberts and D. I. Schuster.
1. Procedure
A solution of
25 g. (0.125 mole) of pyrene (Note
1) in
100 ml. of dimethylformamide (Note
2) and (Note
3) is treated with a
50% excess of ozone (Note
4). The solution of the ozonide is added at a moderate rate, with stirring, to
500 ml. of 1% aqueous acetic acid. The suspension is allowed to stand overnight (Note
5), and the resulting solid is collected by filtration and washed with water.
The moist solid is suspended in
200 ml. of 10% aqueous potassium hydroxide solution, and the suspension is boiled for 5 minutes. The hot solution is filtered, and the remaining solid is again extracted, using
100 ml. of potassium hydroxide solution.
To the dark-brown combined filtrates is added
100 ml. of potassium hypochlorite solution (Note
6), and the resulting solution is permitted to stand overnight. The mixture is then heated on a
steam bath for 4 hours. The resulting orange solution is filtered while hot, and
100 ml. of 35% sodium hydroxide solution is added. The solution is cooled to 5°, the resulting solid is collected by filtration and washed with a small amount of saturated
sodium chloride solution.
The moist sodium salt is digested with
50 ml. of cold 6N hydrochloric acid, and after several hours the mixture is filtered and the resulting solid acid dried.
The crude acid is dissolved in
100 ml. of boiling dimethylformamide, and
100 ml. of hot glacial acetic acid is added. Water is added to the hot solution until it becomes cloudy, and then just enough
dimethylformamide is added to render the solution clear again. It is cooled to 5°, and the resulting acid collected by filtration and washed with glacial
acetic acid. Upon drying,
10–11.5 g. (
32–38%) of
5-formyl-4-phenanthroic acid (Note
7), melting at
272–276° (Note
8), is obtained.
2. Notes
1. Technical
pyrene, Reilly Tar and Chemical Corp., was employed. Purification did not improve the over-all yield, and purer
pyrene is not sufficiently soluble in
dimethylformamide.
2. Freshly distilled
dimethylformamide should be employed. The yields with the technical grade solvent were very erratic.
3. Complete solution is attained by heating the mixture for 5 minutes on a
steam bath.
4. An ozonizer similar to that described by Henne and Perilstein
2 was employed. At an
oxygen flow rate of 30 l./hr. it produced about
30 millimoles of O3 per hour (3% conversion). Under these conditions the ozonization of
25 g. of pyrene requires about 6 hours.
5. Filtration of the hydrolyzate immediately after decomposition is difficult because of the fine nature of the solid. Upon standing, coagulation takes place to yield a granular brown solid.
6. The
potassium hypochlorite solution was prepared
3 from the
calcium hypochlorite sold by Mathieson Chemical Corporation under the trade name HTH. If the HTH reagent used is not fresh, it is found that subsequent heating of the filtrate with the
potassium hypochlorite solution does not result in an orange solution. The solution remains dark brown, and the product is distinctly brown. The yield is not affected.
8. The checkers found that the melting point depends on the rate of heating. A reproducible melting point was obtained if the sample was placed in the bath at 270° and the temperature raised at the rate of two degrees per minute.
3. Discussion
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