Potassium Sodium Tartrate1

[304-59-6]  · C4H4KNaO6  · Potassium Sodium Tartrate  · (MW 210.17) (.4H2O)

[6381-59-5]  · C4H12KNaO10  · Potassium Sodium Tartrate  · (MW 282.25)

(chelating agent for metal ions)

Alternate Names: Rochelle salt; Seignette salt.

Physical Data: tetrahydrate:1c mp 70-80 °C; loses 3H2O at 100 °C; becomes anhydrous at 130-140 °C; dec 220 °C; d 1.79 g cm-3. The physicochemical properties of this tartrate salt are well documented.1b

Solubility: (g 100 mL-1 H2O) 42 at 0 °C, 82 at 16 °C, 140 at 29 °C, 225 at 40 °C;11 insol alcohol.

Form Supplied in: the tetrahydrate is widely available as translucent crystals or as a white crystalline solid.

Analysis of Reagent Purity: by nonaqueous titration.2

Purification: can be recrystallized from a chilled solution of distilled H2O.3

Handling, Storage, and Precautions: purgative; reactions should be performed in a well-ventilated fume hood.


Tartrate esters and metal salts of tartaric acid have found increasing synthetic use as metal chelating agents. Although Rochelle salt has been extensively studied with regard to its electrical, magnetic, and optical properties, and has found industrial utility, e.g. in photography, ceramics, electrodeposition, and analytical spectrophotometry, its use in organic synthesis has been limited. It is perhaps best known as a constituent of Fehling's solution (alkaline copper(II) tartrate), the classic reagent for the characterization of aldehydes.1a,4

Chelating Agent.

The complexing ability of the tartrate ion has been utilized in the workup of reactions involving metal alkoxides. For example, in the Oppenauer oxidation of cholesterol,5 a saturated aqueous solution of Rochelle salt was used to keep the resulting aluminum byproduct in the aqueous layer during the workup (eq 1). The D4-cholesten-3-one was thus readily isolated by extraction and subsequent crystallization in ca. 80% yield.

In a later study,6 after reduction of the cholesten-3-one was accomplished with Lithium Tri-t-butoxyaluminum Hydride, the resulting mixture was hydrolyzed with ice-cold alkaline Rochelle salt (eq 2). The resulting D4-cholesten-3b-ol was easily extracted with ether in 87% yield.

With Rochelle salt workup, 6a-methylandrost-4-ene-3,17-dione has been prepared from the corresponding 5a-hydroxy-6b-methylandrostane derivative in the presence of Aluminum t-Butoxide (eq 3).7 Isolation of the Lithium Aluminum Hydride reduction products of a-silyl esters (eq 4) is also facilitated by ice-cold aqueous Rochelle salt.8

In a synthesis of a leukotriene antagonist, introduction of the required asymmetric center was achieved by chiral reduction of the ketone precursor with (-)-B-chlorodiisopinocampheylborane eq 5).9 Acetone quenching and addition of 20% aqueous Rochelle salt solution allowed isolation of the product alcohol in 87% yield.

Chiral Metal(II) (+)-Tartrate Lewis Acids.

A number of metal(II) tartrates synthesized from Rochelle salt have found recent use as heterogeneous chiral Lewis acid catalysts in the asymmetric ring-opening reactions of meso-epoxides (eqs 6 and 7).10 Thiols, aniline, and trialkylsilyl azides give the corresponding adducts in varying chemical yields and enantiomeric excess using 10 mol % concentrations of metal (+)-tartrate catalyst.

1. (a) Berger, S. E. In Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed.; Grayson, M., Ed.; Wiley: New York, 1981; Vol. 13, pp 80-121. (b) Beilstein Handbook of Organic Chemistry, 4th ed., 4th Suppl.; Springer: New York, 1977; Vol. 3, Part 2, p 1223 and references cited therein. (c) The Merck Index, 11th ed.; Budavari, S., Ed.; Merck: Rahway, NJ, 1989; p 1217.
2. Reagent Chemicals: American Chemical Society Specifications, 8th ed.; American Chemical Society: Washington, 1993; p 599.
3. Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory Chemicals, 3rd ed.; Pergamon: New York, 1988; p 340.
4. Furniss, B. S.; Hannaford, A. J.; Smith, P. W. G.; Tatchell, A. R. Vogel's Textbook of Practical Organic Chemistry, 5th ed.; Wiley: New York, 1989; p 1219.
5. Eastman, J. F.; Teranishi, R. OSC 1963, 4, 192.
6. Burgstahler, A. W.; Nordin, I. C. JACS 1961, 83, 198.
7. Adams, W. J.; Ellis, B.; Petrow, V.; Stuart-Webb, I. A. U.S. Patent 3 270 037, 1966.
8. Tanaka, J.; Kanemasa, S.; Ninomiya, Y.; Tsuge, O. BCJ 1990, 63, 476.
9. King, A. O.; Corley, E. G.; Anderson, R. K.; Larsen, R. D.; Verhoeven, T. R.; Reider, P. J.; Xiang, Y. B.; Belley, M.; Leblanc, Y.; Labelle, M.; Prasit, P.; Zamboni, R. J. JOC 1993, 58, 3731.
10. Yamashita, H. BCJ 1988, 61, 1213.
11. Shul'vas-Sorokina, R. D. Zh. Fiz. Khim. 1934, 5, 1438 (CA 1935, 29, 5721).

Woo-Baeg Choi

Merck Research Laboratories, Rahway, NJ, USA

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