Lead(II) Acetate


[301-04-2]  · C4H12O7Pb  · Lead(II) Acetate  · (MW 379.33)

(desulfurization reagent2,3)

Physical Data: mp 75 °C when rapidly heated; above 100 °C it begins to lose acetic acid and decomposes completely above 200 °C; d 2.55 g cm-3.

Solubility: 0.456 g mL-1 in H2O at 15 °C; 2.0 g mL-1 in H2O at 100 °C; 0.033 g mL-1 in ethanol; slightly sol diethyl ether; freely sol glycerol.

Form Supplied in: colorless crystals or white granules or powder; slowly effloresces; widely available; may contain insoluble lead carbonate resulting from exposure to air. Drying: dry at rt because of facile dehydration. Drying over H2SO4 at rt leads to formation of the anhydride.

Purification: recrystallize from water containing 2-3% acetic acid.

Handling, Storage, and Precautions: poisonous; carcinogen; LD50 200 mg kg-1 (intraperitoneal in rats); avoid breathing dust and handle only in a fume hood. Keep tightly closed for storage; readily converts to complex salts. Incompatible with acids, alkalies, sulfates, sulfites, citrates, tartrates, chlorides, carbonates, tannin, phosphates, resorcinol, salicylic acid, and phenol.

Neutralization of HCl.1

In the synthesis of a-aminodiethylacetic acid via acid hydrolysis of the cyanohydrin of diethyl ketone, the crude amino acid hydrochloride is neutralized by lead hydroxide (prepared by hydrolysis of this reagent with sodium hydroxide) to yield the amino acid in liberated form (eq 1). This procedure appears to be superior to that using Lead(IV) Oxide for this neutralization.

Removal of Selenium and Selenious Acid.2

Selenium(IV) Oxide and selenious acid are good reagents for the oxidation of the a-methylene carbon of carbonyl compounds to give 1,2-dicarbonyl compounds. However, it is difficult to remove the resulting colloidal selenium and excess of the oxidant from the desired product in this method. A procedure for the oxidation of paraldehyde to glyoxal and the isolation of the product as the bis-bisulfite addition compound specifies the use of lead(II) acetate. Thus the addition of aqueous solution of this reagent to the reaction mixture gives insoluble lead selenite as a precipitate which is removed readily by filtration.

Conversion of Isocyanides into Isothiocyanates.3

Reactions of isocyanides with dibenzoyl disulfide occur smoothly in the presence of this reagent to give isothiocyanates in high yield (eq 2). The activity of this reagent is almost identical with that of Thallium(I) Acetate. In this reaction, a complex of the reagent with dibenzoyl disulfide is believed to be the key intermediate in the sulfurization of the isocyanide (eq 3).

Elimination of H2S.4

This reagent is used for the conversion of thioureas to cyanamides by elimination of H2S under mild conditions, as illustrated in eq 4.

Acetoxylation of Allylic Bromide.5

This reagent is used for the preferential replacement of a bromine atom by an acetoxy group in 1-chloro-3-bromocycloalkenes (eq 5). Lead(II) acetate is superior to Silver(I) Acetate for this transformation.

Preparation of Cyclic Disulfides.6

Reactions of dithiols with an aqueous solution of this reagent give lead dithiolates in nearly quantitative yield. The dithiolates react with sulfur in benzene at rt to give the cyclic disulfides in high yields without the formation of polymeric disulfides (eq 6).

1. Steiger, R. E. OSC 1955, 3, 66.
2. Ronzio, A. R.; Waugh, T. D. OSC 1955, 3, 438.
3. Tanaka, S.; Uemura, S.; Okano, M. BCJ 1977, 50, 2785.
4. Kurzer, F. OSC 1963, 4, 172.
5. Schank, K.; Eistert, B.; Felzmann, J. H. CB 1966, 99, 1414.
6. Cragg, R. H.; Weston, A. F. TL 1973, 655.

Tatsuo Oida

Kyoto Institute of Technology, Japan

Sakae Uemura

Kyoto University, Japan

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