Organic Syntheses, Coll. Vol. 5, p.810 (1973); Vol. 43, p.80 (1963).
An autoclave (Note 1)
is charged with 200 g. (1.28 moles) of 2,3-dimethylnaphthalene (Note 2)
, 940 g. (3.14 moles, 23% excess) of sodium dichromate dihydrate
, and 1.8 l. of water. The autoclave is closed, heated to 250°, and shaken continuously at this temperature for 18 hours. The autoclave is cooled with continued agitation (Note 3)
, the pressure is released, and the autoclave is opened. The contents are transferred to a large vessel (Note 4)
. To effect complete transfer, the autoclave is rinsed with several 500-ml. portions of hot water. Green hydrated chromium oxide
in the reaction mixture is separated on a large Büchner funnel
and washed with warm water until the filtrate is colorless. The combined filtrates (7–8 l.) are acidified with 1.3 l. of 6N hydrochloric acid
. The acidified mixture is allowed to cool to room temperature overnight. The 2,3-naphthalenedicarboxylic acid
that has precipitated is collected on a large Büchner funnel, washed with water until the filtrate is colorless, and dried to constant weight in a vacuum oven
at 50°/20 mm. or by long standing in air. The 2,3-naphthalenedicarboxylic acid
is a white powder; m.p. 239–241°
; weight 240–256 g.
An autoclave fitted for stirring or shaking is essential for good yields. The submitter used a hydrogenation autoclave of the type supplied by the American Instrument Company, catalog No. 406-21, having a capacity of 3.2 l. The autoclave is shaken by means of a "Bomb Shaker" in which it is placed. If a stirred autoclave or "Magne-Dash" is used, the reaction time can be shortened to 3–5 hours. At 250° the gauge pressure is about 600 lb./in.2
. The checkers' yield was 92% in a shaker tube, but only 75% in a rocker tube; the latter yield was raised to 82% by extending the reaction time to 40 hours.
This oxidation does not poison the autoclave for subsequent hydrogenations.
Material produced by Ruetgerswerke A. G. is satisfactory. This can be obtained in the United States from Terra Chemicals Inc., New York, New York; Aldrich Chemical Co., Milwaukee 10, Wisconsin; and K and K Laboratories Inc., Jamaica 33, New York.
It is convenient to empty the autoclave while the contents are still warm.
Commercially available 10-quart polyethylene pails are very satisfactory.
4. Merits of the Preparation
This procedure illustrates a general method for the preparation of aromatic carboxylic acids by oxidation of the corresponding alkylarenes.2
For example, 2-naphthoic acid
yield; m.p. 184–185°
) was obtained from 2-methylnaphthalene (320 g., 2.25 moles)
, sodium dichromate (975 g., 3.26 moles, 45% excess)
, and water (1.8 l.).
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