Org. Synth. 1953, 33, 47
DOI: 10.15227/orgsyn.033.0047
1,5-NAPHTHALENEDITHIOL
Submitted by P. D. Caesar
1
Checked by Richard T. Arnold, W. E. Parham, and R. M. Scribner.
1. Procedure
A
2-l. round-bottomed flask having standard-taper, ground-glass fittings is equipped with a bulb condenser (Note 1) and an
efficient Hershberg stirrer. To this are added with stirring
600 g. (2.0 moles) of 33% sulfuric acid,
20 g. (0.06 mole) of finely divided 1,5-naphthalenedisulfonyl chloride (p. 693 ), and
100 g. (1.5 g. atoms) of zinc dust amalgam (Note 2) at room temperature
(Note 3). The
zinc dust amalgam is added directly after the disulfonyl chloride in the course of 2–5 minutes. The mixture is heated to reflux, held there for about 6 hours, and allowed to cool overnight without agitation
(Note 4).
The product is filtered, and the precipitate is extracted with a total of 1 l. of warm ether (Note 5). The combined ether extracts are evaporated to a volume of 50 ml., cooled, and filtered. The filtrate is further evaporated to a volume of about 10 ml., cooled, and again filtered. The precipitates melt at 119–121° and total 7.1–9.1 g. This represents a yield of 60–77%.
The 1,5-naphthalenedithiol can be further purified to a melting point of 120–121° by sublimation under high vacuum in a molecular still, followed by reprecipitation of the water-soluble disodium salt of the sublimate from excess hydrochloric acid. The pure compound obtained from 9.1 g. of product weighs 8.6 g. (73%).
2. Notes
1.
The product collects in the condenser, and it may be necessary to clear the condenser with a
glass rod.
2.
A good grade of
zinc and
mercury(II) chloride should be used. The
zinc dust amalgam is prepared by dissolving
20 g. of mercury(II) chloride in a solution of
10 ml. of concentrated hydrochloric acid in 300 ml. of distilled water, and adding quickly, with stirring,
100 g. of zinc dust (Schaar chemicals, 95% purity). After 10–15 minutes of stirring and crushing lumps, the mixture is filtered through a
Büchner funnel, and the
zinc dust amalgam is carefully washed with a total of 500 ml. of distilled water containing a trace of
hydrochloric acid. The water is then removed by
ethanol, the
ethanol by
ether, and most of the
ether by air. It is advisable to remove the
zinc dust amalgam from the Büchner funnel and add it to the reduction mixture before all the
ether is removed to assure minimum contact with the air.
An occasional batch of zinc dust failed to effect the desired reduction, possibly because of excessive oxide deposition on the surface of the zinc. It is suggested, therefore, that the surface of the zinc dust be cleaned with dilute hydrochloric acid just before amalgamation.
3.
This technique eliminates the long induction period at 0° and the violent foaming described in the preparation of
thiophenol.
2 However, in a larger-scale operation it would be advisable to check the rate of addition of the
zinc dust somewhat, lest an exception arise.
4.
The overnight period was a matter of convenience and is not considered to be vital to the completeness of the reaction.
5.
When unamalgamated
zinc dust is used, a considerable proportion of yellow insoluble product is often noted at this point. Since the disulfide has been isolated as an intermediate in a similar reduction of
m-chlorosulfonylbenzoic acid,
3 it is probable that this material is a mixture of disulfides of varying molecular weight.
3. Discussion
This method has been applied successfully to the preparation of
phenoxybenzene-4,4'-dithiol (
84% of the theoretical amount),
diphenylmethane-4,4'-dithiol, and
m-sulfhydrylbenzoic acid3 (
80%). It did not prove satisfactory for the preparation of higher-melting thiols of lower solubility, such as
2,7-naphthalenedithiol,
2,6-naphthalenedithiol, and
4,4'-biphenyldithiol. These were better prepared by the use of
tin(II) chloride 2-hydrate in glacial acetic acid saturated with
hydrogen chloride.
41,5-Naphthalenedithiol can be prepared by adding
1,5-naphthalenedisulfonyl chloride to an
ethanol solution of
tin(II) chloride 2-hydrate saturated with
hydrogen chloride.
5 An
80% yield of the crude dithiol melting at
103° was previously reported using
zinc dust and
sulfuric acid.
6
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
phenoxybenzene-4,4'-dithiol
diphenylmethane-4,4'-dithiol
m-sulfhydrylbenzoic acid
tin(II) chloride 2-hydrate
ethanol (64-17-5)
sulfuric acid (7664-93-9)
hydrogen chloride,
hydrochloric acid (7647-01-0)
acetic acid (64-19-7)
ether (60-29-7)
zinc (7440-66-6)
mercury(II) chloride (7487-94-7)
Thiophenol (108-98-5)
1,5-Naphthalenedisulfonyl chloride (1928-01-4)
1,5-Naphthalenedithiol (5325-88-2)
2,7-naphthalenedithiol
2,6-naphthalenedithiol
m-chlorosulfonylbenzoic acid (4025-64-3)
4,4'-biphenyldithiol
Copyright © 1921-, Organic Syntheses, Inc. All Rights Reserved