Ammonium Sulfide

(NH4)2S

[12135-76-1]  · H8N2S  · Ammonium Sulfide  · (MW 68.14)

(redox agent for alkyl and carbonyl groups in the Willgerodt reaction;1 reducing agent for nitro functional group;6 sulfuration agent for many types of functional groups13)

Physical Data: forms crystals (colorless needles) below -18 °C; decomposes into NH4SH, NH3, and ammonium polysulfides at high temperature.

Solubility: sol cold water, ethanol, liquid ammonia; reacts with water to give NH4SH and NH4OH.

Form Supplied in: the solution in water (20 wt %) is called ammonium sulfide solution - red and contains about 30% (NH4)2S, whereas ammonium sulfide - yellow contains 16-20% (NH4)2S.

Handling, Storage, and Precautions: decomposes into ammonia and ammonium polysulfide in air under light (sunlight); the solution of ammonium sulfide in water is strongly alkaline; keep container tightly closed and in a cool place; odor of NH3 and H2S.

Reduction of Carbonyl Functional Groups.

Towards the end of the 19th century, ammonium polysulfide (which usually contains ammonium sulfide) was found to react with aryl alkyl ketones as a redox agent, reducing carbonyls to methylene groups and oxidizing terminal alkyls to carbonyl groups to form the corresponding amides.1 This reaction is the Willgerodt reaction and has been proposed as a convenient method for the synthesis of amides from ketones, as shown in eq 1.

Similarly, ammonium sulfide has been widely employed to produce various amides and acids, by acting as a redox agent for many types of compounds; for example, aryl alkyl ketones give the corresponding aryl-substituted amides, with yields according to the substituent, as shown in eq 2.2 Furthermore, unsaturated carboxylic acids (eq 3),3 aldehydes (eq 4),4 carbinols,5 thiols,9 amines,6 alkylbenzenes (eq 5),7 and alkyl halides (eq 6)7,8 were also found to react with ammonium sulfide to give the corresponding amides.

Interestingly, Cerwonka et al. reported a 14C-tracer (C*) study showing that the two terminal methyl groups are oxidized to carbonyl groups to give two products and that a short carbon chain is more reactive than a long chain in the molecule (eq 7).9 Although there have been many reports on the Willgerodt reaction and some reaction mechanisms have been proposed, the exact mechanism is not yet clear.

Reduction of Nitro Functional Group.

Ammonium sulfide is used as a good selective reducing agent of a nitro functional group to an amine. For example, 4-nitrophenylacetic acid is reduced selectively with ammonium sulfide to give 4-aminophenylacetic acid in high yield (eq 8).10

Interestingly, 3-nitrofluorene reacts with ammonium sulfide in DMF to give 3-(N-hydroxylamino)fluorene selectively and then can be treated with 14C-labeled MeC*OCl to form 3-(N-acetylhydroxylamino)fluorene having a 14C-labeled acetyl group (content 98%) in 58% yield (eq 9).11 This reaction is important as a convenient method to supply 14C-labeled compounds.

The treatment of 4-chloro-3,5-dinitrotrifluoromethylbenzene with ammonium sulfide in dioxane-H2O affords the cyclization-dimerization product 1,6-dinitro-3,8-bis(trifluoromethyl)phenothiazine in 25% yield, while similar treatment in the presence of acetone gives 2,2-dimethyl-7-nitobenzothiazoline in 50% yield (eq 10).12

Sulfuration Agent.

The treatment of a gold(II) phosphorus ylide dimer with ammonium sulfide in THF results in the formation of a symmetrical gold(II) phosphorus ylide (60% yield) containing four- and five-atom polysulfide bridges. The coordination geometry about the gold centers in this structure is best described as square planar. The overall configuration of ylide units is shown to be a twisted boat (eq 11).13

In the presence of ammonium sulfide, bis(cyclopentadi-enyl)titanium pentasulfide, which is formed by the reaction of bis(methylcyclopentadienyl)titanium dichloride with ammonium sulfide, reacts with acetone to give (MeCp)2TiS4CMe2 in 42% yield (eq 12).14

N-Alkyldithiooxamides are synthesized in good yield by reaction of cyanodithioformates with alkylamine and ammonium sulfide (eq 13).15 Benzoylphenylalkynes react with ammonium sulfide in 60% dioxane-water at 15 °C to give a mixture of the b-hydroxy-a-thiobenzoylstyrene derivative (30%) and (E,Z)-b,b-di(a-benzoylstyryl) sulfide (65%), as shown in eq 14, whereas only the b-hydroxy-a-thiobenzoylstyrene derivative is formed with sodium sulfide.16


1. Willgerodt, C. CB 1887, 20, 2467.
2. (a) King, J. A.; McMillan, F. H. JACS 1946, 68, 2335. (b) Nightingale, D.; Carpenter, R. A. JACS 1949, 71, 3560. (c) Blanchette, J. A.; Brown, E. V. JACS 1951, 73, 2779.
3. Davis, C. H.; Carmack, M. JOC 1947, 12, 76.
4. Blanchette, J. A.; Brown, E. V. JACS 1952, 74, 2098.
5. (a) King, J. A.; McMillan, F. H. JACS 1946, 68, 525. (b) King, J. A.; McMillan, F. H. JACS 1946, 68, 632. (c) Pattison, D. B.; Carmack, M. JACS 1946, 68, 2033. (d) McMillan, F. H.; King, J. A. JACS 1948, 70, 4143.
6. Naylor, M. A.; Anderson, A. W. JACS 1953, 75, 5392.
7. Naylor, M. A.; Anderson, A. W. JACS 1953, 75, 5395.
8. (a) Gerry, R. T.; Brown, E. V. JACS 1953, 75, 740. (b) Milligan, B.; Swan, J. M. JCS 1961, 1194.
9. Cerwonka, E.; Anderson, R. C.; Brown, E. V. JACS 1953, 75, 28.
10. Plattner, A.; Armstrong, E. C. Dehydrogenation with Sulfur, Selenium, and Platinum Metals, Newer Methods of Preparative Organic Chemistry; Interscience: New York, 1948; p 21.
11. Thissen, M. R.; Roth, R. W.; Duncan, W. P. OPP 1980, 12, 337.
12. Chen, M.; Chi, C.; Chen, Q. PS 1990, 48, 173.
13. Fackler, J. P. Jr.; Porter, L. C. JACS 1986, 108, 2750.
14. Giolando, D. M.; Rauchfuss, T. B. OM 1984, 3, 487.
15. Kibbel, H. U.; Kücken, M.; Peters, E.; Weber, H. JPR 1981, 323, 41.
16. Baddar, F. G.; Al-Hajjar, F. H.; El-Rayyes, N. R. JHC 1976, 13, 691.

Ryu Sato

Iwate University, Morioka, Japan



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