CALCIUM HYPOCHLORITE 1
excess MeOH, methyl esters5 are obtained (eq 2), while with t-
Calcium Hypochlorite1
butanol, carboxylic acids4 are generated (eq 3). A variety of sub-
stituted methyl benzoates are thus easily prepared from the cor-
Ca(OCl)2
responding benzyl alcohols by the former method, and t-butyl
esters are available from aldehydes.5 Aldehydes, which are easily
oxidized to carboxylic acids6 with Ca(OCl)2 (eq 4), are them-
[7778-54-3] CaCl2O2 (MW 142.99)
selves available in remarkably high yield from primary alcohols,
InChI = 1/Ca.2ClO/c;2*1-2/q+2;2*-1
in less than 15 min, when a catalytic amount of 4-(benzoyloxy)-
InChIKey = ZKQDCIXGCQPQNV-UHFFFAOYAV
2,2,6,6-tetramethylpiperidin-1-oxyl is added (eq 5).2 (Ruthe-
nium(III) Chloride has also been used to catalyze this reaction.13)
(oxidizing agent for the conversion of alcohols to aldehydes,2
ketones,3 carboxylic acids,4 esters,3 and methyl esters;5 aldehy-
des to acids6 and t-butyl esters;5 ethers to esters,3 and thioethers Ca(OCl)2, 0 °C, 1 h
Pentyl pentanoate
1-Pentanol (1)
to sulfoxides;7 for the C C bond cleavage of 1,2-dioxygenated
MeCN, H2O, AcOH
compounds;8 for the chlorination of benzenoid compounds;1 for 83%
the conversion of alkenes to chlorohydrins9)
Alternative Names: calcium oxychloride; hypochlorous acid, O
Ca(OCl)2, rt, 24 h
O
HO
calcium salt; B-K powder.
dark, AcOH, MeOH
ć%
Physical Data: mp 100 C; specific gravity 2.35.
O
MeO
82%
Solubility: insol organic solvents; slightly sol H2O (with decom-
O
O
position); very sol H2O with a few drops of HOAc; aqueous
MeO2C
(2)
solutions of acetic acid, acetonitrile, acetone, MeOH, and t-
O
MeO
butanol, and biphasic solutions of H2O with EtOAc, CH2Cl2,
ether, benzene, and CCl4 are used for oxidations.
Ca(OCl)2, rt, 6 h
Form Supplied in: white or light yellow granular solid with strong
Cyclohexylmethanol Cyclohexanecarboxylic
chlorine odor; widely available. t-BuOH, H2O
acid
(3)
83%
Purification: composition is generally 60 70% Ca(OCl)2
[Ca(OCl)2, 65%; NaCl, 15%; H2O, 10%; Ca(OH)2, 4%;
CaCO3, 3%; CaClO3, 1.5%; CaCl2, 1%].10
Ca(OCl)2, 0 °C, 1 h
(4)
RCHO RCO2H
Handling, Storage, and Precautions: commercially available
MeCN, H2O, AcOH
Ca(OCl)2 (65%) is easy to handle and may be stored in
R = 3-pentyl 75%
a desiccator without substantial decomposition.11 Anhydrous
R = p-ClC6H4 92%
Ca(OCl)2 must be stored in a brown bottle kept away from
R = m-NO2C6H4 84%
sunlight and moisture. It explodes when in direct contact with
organic material, especially lubrication oils. This reagent
Ca(OCl)2, 5 °C, 5 min
should be handled in a fume hood.
Me(CH2)10 CH2OH
CH2Cl2, H2O, HCO3 , cat
96%
General Conditions of Use. Ca(OCl)2 is an inexpensive and
(5)
Me(CH2)10 CHO
broad-based reagent for the oxidation of a variety of functional
groups.1 9 Its advantage over Sodium Hypochlorite (NaOCl) is
its relative stability at ambient temperature11 and its ease of han-
Secondary alcohols afford ketones3 in high yield in aqueous
dling as a solid. NaOCl is commercially available in dilute aque-
media (eq 6), or in organic media (CH2Cl2, CCl4, Et2O, EtOAc)
ous solutions (usually about 3 5%) that deteriorate rather rapidly.
with a catalytic amount of  hypochlorite resin (IRA 900)14 us-
Thus the solution must be frequently titrated to define the quan-
ing a triphasic system (liquid solid solid) (eq 7). Acyclic and
tity of oxidant present. In addition, because of the low concen-
cyclic ethers give esters (eq 8)3 and lactones (eq 9),3 respectively,
tration of NaOCl in solution an excessive volume of solvent is
although the yields are lower than for the oxidation of the other
usually present.12 The major difficulty encountered with the use
groups. A variety of alkyl and aryl-alkyl thioethers can be selec-
of Ca(OCl)2 is that of solubility. It is insoluble in most common
tively oxidized to sulfoxides (eq 10)7 in yields exceeding 70%
organic solvents and forms a cloudy solution in water. However,
however, dibenzyl sulfide is inefficiently converted to dibenzyl
complete solubility in water is attained by the addition of a few
sulfoxide (25%).
drops of acetic acid, giving a final oxidizing solution that is clear
and light yellow. Aqueous organic biphasic solutions are also use-
Ca(OCl)2, 0 °C, 1 h
Borneol Camphor (6)
ful media in which to carry out the oxidations.
MeCN, H2O, AcOH
98%
Oxidation of Alcohols, Ethers, Thioethers, and Aldehydes.
Ca(OCl)2 efficiently oxidizes primary alcohols to esters3 (eq 1),
Ca(OCl)2, rt, 3 h
where both the acid and alcohol portion of the ester are derived
Cyclopentanol Cyclopentanone (7)
CCl4, IRA 900
from the alcohol. In the presence of Molecular Sieves and with
90%
Avoid Skin Contact with All Reagents
2 CALCIUM HYPOCHLORITE
Ca(OCl)2, rt, 1 h
HO
Butyl butanoate (8)
(n-Bu)2O
MeCN, H2O, AcOH
O
Ca(OCl)2, rt, 1 h
Isosafrole
40% (14)
glycol MeCN, H2O, CH2Cl2 OH
O
Cl
85%
Ca(OCl)2, rt, 1 h
Å‚-Butyrolactone (9)
THF R1 R1
MeCN, H2O, AcOH
Ca(OCl)2, 0 °C, 1 h
68%
R2 R R2 R
acetone, H2O, AcOH
R = Me, R1 = R2 = H 50% R = Me, R1 = H, R2 = Cl (15)
R = HNAc, R1 = R2 = H 79% R = HNAc, R1 = H, R2 = Cl (16)
Ca(OCl)2, reflux, 1.5 h
(10)
R = OMe, R1 = R2 = H 68% R = OMe, R1 = H, R2 = Cl (17)
Bu2SBu2S=O
EtOAc
R = Me, R1 = H, R2 = CHO 76% R = Me, R1 = Cl, R2 = CO2H (18)
100%
R = OMe, R1 = CHO, R2 = H 93% R = OMe, R1 = CHO, R2 = Cl (19)
Conversion of Alkenes to Chlorohydrins. Ca(OCl)2
Carbon Carbon Bond Cleavage Reactions. Ä…-Diols, Ä…-
converts mono-, di-, tri-, and tetrasubstituted, cyclic, and acyclic
diones,Ä…-hydroxy ketones, andÄ…-hydroxy andÄ…-keto acids8 are
alkenes to the corresponding chlorohydrins9 in good yield (eqs
oxidatively cleaved with Ca(OCl)2 (eqs 11 and 12). The yields are
20 23). The reactions are carried out under mild conditions and
good to excellent and the products obtained (aldehydes, ketones,
the expected regiochemistry is obtained.
acids) depend on the oxidation state of the carbon atoms bearing
the original oxygen groups. In an interesting two-step high-yield
Ca(OCl)2, 0 °C, 1 h
preparation of piperonal, the glycol obtained from electrochemical
4-Methyl-1-pentene 1-Chloro-4-methyl-2-pentanol
acetone, H2O, AcOH
oxidation of isosafrole is converted to piperonal in near quanti-
(20)
82%
tive yield by glycol cleavage15 when treated with Ca(OCl)2 in
benzene/H2O (eq 13).
Ca(OCl)2, 0 °C, 1 h
Cyclododecene 2-Chlorocyclododecanol
(21)
acetone, H2O, AcOH
Ca(OCl)2, rt, 2 h
89%
Benzopinacol Benzophenone (11)
MeCN, H2O, AcOH
92%
Ca(OCl)2, 0 °C, 1 h
1-Methylcyclohexene
acetone, H2O, AcOH
70%
Ca(OCl)2, rt, 3 h 2-Chloro-1-methylcyclohexanol (22)
Sodium Ä…-ketovalerate Butyric acid (12)
MeCN, H2O, AcOH
96%
Ca(OCl)2, 0 °C, 1 h
2,3-Dimethyl-2-butene
acetone, H2O, AcOH
72%
OH
3-Chloro-2,3-dimethyl-2-butanol (23)
CHO
O O
Ca(OCl)2, 65 °C, 1 h
(13)
benzene, H2O
OH
O O
98%
Piperonal
1. Nwaukwa, S. O.; Keehn, P. M., Synth. Commun. 1989, 19, 799.
2. Inokuchi, T.; Matsumoto, S.; Nishiyama, T.; Torii, S., J. Org. Chem.
1990, 55, 462.
Chlorination of Benzenoid Compounds. As depicted
3. Nwaukwa, S. O.; Keehn, P. M., Tetrahedron Lett. 1982, 23, 35.
in eq 14, if the glycol of isosafrole is oxidized in
4. Kabalka, G. W.; Chatla, N.; Wadgaonkar, P. P.; Deshpande, S. M., Synth.
MeCN/CH2Cl2/H2O at ambient temperature, ring chlorination15
Commun. 1990, 20, 1617.
takes place instead of C C bond cleavage to afford 1-
5. McDonald, C. E.; Nice, L. E.; Shaw, A. W.; Nestor, N. B., Tetrahedron
[2-chloro-4,5-(methylenedioxy)phenyl]propane-1,2-diol (85%).
Lett. 1993, 34, 2741.
Ca(OCl)2 can thus be used for chlorination of aromatics (ben-
6. Nwaukwa, S. O.; Keehn, P. M., Tetrahedron Lett. 1982, 23, 3131.
zene, naphthalene).1 While chlorobenzene, nitrobenzene, and 4-
7. Weber, J. V.; Schneider, M.; Salami, B.; Paquer, D., Recl. Trav. Chim.
nitrotoluene do not react, good results are obtained when the sub- Pays-Bas 1986, 105, 99.
strate has strong electron-donating substituents (eqs 15 17).1 Ac- 8. Nwaukwa, S. O.; Keehn, P. M., Tetrahedron Lett. 1982, 23, 3135.
tivated rings having oxidizable substituents will undergo chlori- 9. Nwaukwa, S. O., Int. J. Chem. 1990, 1, 37.
nation and oxidation, depending on the reactivities of the groups
10. Fisher Scientific Chemical Division, 1 Reagent Lane, Fair Lawn NJ
and the number of equivalents of Ca(OCl)2 used (eqs 18 and 19). 07410.
A list of General Abbreviations appears on the front Endpapers
CALCIUM HYPOCHLORITE 3
11. There was no change in concentration of oxidant for Ca(OCl)2 when 15. Torii, S.; Uneyama, K.; Ueda, K., J. Org. Chem. 1984, 49, 1830.
titrations were carried out over a period of 2/12; months. See Vogel,
A. I. A Textbook of Quantitative Inorganic Analysis, 3rd ed.; Wiley:
New York, 1961.
Philip M. Keehn
12. Stevens, R. V.; Chapman, K. T.; Weller, H. N., J. Org. Chem. 1980, 45,
Ondo State University, Ado-Ekiti, Nigeria
2030.
Stephan O. Nwaukwa
13. Genet, J. P.; Pons, D.; Jugé, S., Synth. Commun. 1989, 19, 1721.
Brandeis University, Waltham, MA, USA
14. Schneider, M.; Weber, J.-V.; Faller, P., J. Org. Chem. 1982, 47, 364.
Avoid Skin Contact with All Reagents