Submitted by Frank C. Whitmore, P. J. Culhane, and H. T. Neher.
Checked by Henry Gilman and C. C. Vernon.
1. Procedure
A solution of
80 g. (2 moles) of sodium hydroxide in 800 cc. of water is prepared in a
2-l. beaker. To the warm solution is added
211 g. (1 mole) of 3-nitrophthalic acid (p. 408) (Note
1). A small amount of insoluble material is removed by filtration through a large preheated
Büchner funnel (Note
2). A solution of
350 g. (1.1 moles) of mercuric acetate (Note
3) in a mixture of
50 cc. of glacial acetic acid and 700 cc. of water is prepared by heating and filtering while hot (Note
4). The two hot solutions are poured into a
3-l. long-necked flask and mixed by shaking. No precipitate should separate (Note
5). The flask is clamped in a large
oil bath (Note
6) with the level of the oil almost to the neck of the flask. It is fitted with a
reflux condenser provided with a tube leading to a large beaker placed on the desk (Note
7).
The temperature of the oil bath is raised to 170° over a period of about one hour. If any considerable amount of material is driven through the condenser, it is poured back through the top of the condenser as soon as the reaction slackens. The heating at 165–175° is continued for about seventy hours. After about sixty hours the end of the tube leading from the top of the condenser is introduced below the surface of about
1 cc. of mercury in a small
test tube. The evolution of
carbon dioxide can be followed by observing the bubbles which pass through the
mercury. When not more than one or two bubbles escape per minute, the heating is discontinued (Note
8).
The product is allowed to settle and the hot supernatant liquid is poured through a preheated
suction filter. The filtrate deposits less than
10 g. of crude product on cooling. The product in the flask is shaken with several 100-cc. portions of water, and all the fine material is transferred to the filter. Some lumpy material is usually left in the flask. This is transferred to a large
mortar and ground to a paste with a little water and then transferred to the filter. After sucking as dry as possible, the suction is shut off, and
100 cc. of alcohol is poured over the material on the filter. After standing a few minutes, suction is again applied. The product is then dried to constant weight (Note
9). The yield of
anhydro-2-hydroxymercuri-3-nitrobenzoic acid is
300–330 g. (
82–90 per cent of the theoretical amount based on the
3-nitrophthalic acid used). It is a cream-colored powder which dissolves in an excess of dilute
sodium hydroxide, leaving only a slight turbidity (Note
10) and (Note
11).
2. Notes
2. Although the insoluble material is very small in amount, filtration without suction is too slow.
4. A small amount of
mercurous compounds is removed by the filtration.
5. If more concentrated solutions are used, the
mercuric salt precipitates and the reaction runs less smoothly.
6. A large
galvanized pail containing extra heavy lubricating oil was used. This oil does not fume even after heating for long periods.
7. This beaker serves to catch any material which is carried over during a slightly violent reaction which sometimes takes place at the beginning.
8. If a more accurate indication of the end of the reaction is desired, a tube containing
mercury may be inverted in a small beaker of
mercury and any gas evolved during the later stages of the reaction may be collected over the
mercury.
11. By a similar procedure
phthalic anhydride may be converted into
anhydro-o-hydroxymercuribenzoic acid. Thus,
300 g. (2 moles) of phthalic anhydride and
750 g. (2.2 moles) of commercial mercuric acetate (Note
3) give
550 g. of the
mercury compound (
85 per cent of the theoretical amount). With
phthalic anhydride the reaction is complete in six to ten hours.
3. Discussion
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