LEAD(II) ACETATE

1

Lead(II) Acetate

Pb(OAc)

2

·3H

2

O

[301-04-2]

C

4

H

12

O

7

Pb

(MW 379.33)

InChI = 1/2C2H4O2.3H2O.Pb/c2*1-2(3)4;;;;/h2*1H3,(H,3,4);

3*1H2;/q;;;;;+2/p-2/f2C2H3O2.3H2O.Pb/q2*-1;;;;m

InChIKey = MCEUZMYFCCOOQO-TXGYFSJOCT

(desulfurization reagent

2,3

)

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 H

2

O at 15

◦

C; 2.0 g mL

−1

in H

2

O

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

H

2

SO

4

at rt leads to formation of the anhydride.

Purification:

recrystallize from water containing 2–3% acetic

acid.

Handling, Storage, and Precautions:

poisonous; carcinogen;

LD

50

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 α-aminodiethyl-

acetic 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.

Et

Et

O

Et

Et

NH

2

NC

HCl

Et

Et

NH

3

Cl

–

HO

2

C

Et

Et

OH

NC

NH

3

Pb(OAc)

2

Et

Et

NH

2

HO

2

C

+

NaCN, NH

4

Cl

(1)

39–43%

NaOH

Removal of Selenium and Selenious Acid.

2

Selenium(IV)

Oxide and selenious acid are good reagents for the oxidation
of the α-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 pres-
ence of this reagent to give isothiocyanates in high yield (eq 2).
The activity of this reagent is almost identical with that of Thal-
lium(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).

NC

Ph

S

S

Ph

O

O

NCS

+

Pb(OAc)

2

(2)

89%

Ph

S

S

Ph

O

O

N

C

+

S

Ph

O

Pb(OAc)

2

Ph

S

(AcO)

2

Pb

O

Ph

S

S

Ph

O

O

Pb(OAc)

2

N

–

C

NCS

+

–

(3)

– Pb(OAc)

2

– (PhCO)

2

S

Elimination of H

2

S.

4

This reagent is used for the conver-

sion of thioureas to cyanamides by elimination of H

2

S under mild

conditions, as illustrated in eq 4.

(4)

HN

NH

2

S

Cl

HN

Cl

N

Pb(OAc)

2

, KOH

– PbS

72–74%

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.

Cl

Br

Cl

OAc

(CH

2

)

n

(CH

2

)

n

Pb(OAc)

2

n

= 6–9

(5)

– PbBr

2

80–90%

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).

SH

Pb

S

S

S

S

SH

(CH

2

)

n

(CH

2

)

n

(CH

2

)

n

Pb(OAc)

2

S

n

= 3–6

82–92%

(6)

PhH

Avoid Skin Contact with All Reagents

2

LEAD(II) ACETATE

1.

Steiger, R. E., Org. Synth., Coll. Vol. 1955, 3, 66.

2.

Ronzio, A. R.; Waugh, T. D., Org. Synth., Coll. Vol. 1955, 3, 438.

3.

Tanaka, S.; Uemura, S.; Okano, M., Bull. Chem. Soc. Jpn. 1977, 50,
2785.

4.

Kurzer, F., Org. Synth., Coll. Vol. 1963, 4, 172.

5.

Schank, K.; Eistert, B.; Felzmann, J. H., Chem. Ber. 1966, 99, 1414.

6.

Cragg, R. H.; Weston, A. F., Tetrahedron Lett. 1973, 655.

Tatsuo Oida

Kyoto Institute of Technology, Kyoto, Japan

Sakae Uemura

Kyoto University, Kyoto, Japan

A list of General Abbreviations appears on the front Endpapers