Asian Journal of Chemistry; Vol. 25, No. 4 (2013), 1884-1886
Synthesis of Adipic Acid Catalyzed by Sodium Hypochlorite under Ultrasound Irradiation
2
ZHI-PING LIN1,2,* and JI-TAI LI
1Department of Biology and Chemistry, Baoding University, Baoding 071000, P.R. China
2College of Chemistry and Environmental Science, Hebei University, Baoding 071002, P.R. China
*Corresponding author: E-mail: linzhiping888999@163.com
(Received: 10 December 2011;
Accepted: 5 October 2012)
AJC-12242
Adipic acid was synthesized from cyclohexanol oxidized by sodium hypochlorite in 94 % yield within 4 h under ultrasound irradiation.
Key Words: Adipic acid, Sodium hypochlorite, Synthesis, Ultrasound irradiation.
Sasson15 reported the oxidative cleavage of cycloalkanones to
dicarboxylic acids at 10 ºC using sodium hypochlorite under
phase transfer catalysis conditions, but the reaction time was
INTRODUCTION
Adipic acid is a most important organic synthetic inter-
very long to 24 h15. In this paper we wish to report an efficient
mediate and mainly used for synthetic fibers: nylon-66, other
fields can also be widely used, for example polyurethane,
and practical procedure for the synthesis of adipic acid with
synthetic resin, leather, polyester foam, plastic plasticizers,
the oxidation of cyclohexanol by sodium hypochlorite in water
lubricants, food additives, adhesives, pesticides, dyes, spices,
medicine1.
The adipic acid was synthesized usually by the oxidation
under ultrasound irradiation (Scheme-I).
OH
NaClO/H2O
of cyclohexene, cyclohexanol, cyclohexanone or a mixture of
them or electro-oxidation of cyclohexanol2,3, with nitric acid,
potassium permanganate, molecular oxygen, ozone as the
oxidant. Hydrogen peroxide as a safe, gentle, clean, cheap
and readily available oxidant, can replace traditional high-
polluting oxidants in organic synthesis. But in these over
procedures, the expensive and complex catalysts such as,
peroxotungstates and peroxomolybdates4, ZSM-5 supported
metal ions (M/ZSM-5) and N-hydroxyphthalimide (NHPI)5,
heteropoly complexes6, a carbon supported platinum catalyst7,
Ti-AlSBA15 catalysts8, manganese diimine catalysts9, Co-
substituted β-zeolites catalysts10, Iron-phthalocyanine on
zeolite Y11, tungstic acid/acidic organic additive12, phospho-
tungstic acid13 etc. have to be added in the system.
COOH
COOH
Ultrasound irradiation
Scheme-I
EXPERIMENTAL
Liquid substrates were distilled prior to use. Melting points
were uncorrected. Sonication was performed in Shanghai
BUG40-06 or BUG25-06 ultrasonic cleaner (with a frequency
of 25 kHz, 40 kHz, 59 kHz and a nominal power 250 W).
Typical procedure for the preparation of adipic acid:
A 50 mL two-necked round flask was charged with cyclo-
hexanol (2 mmol) and 10 % sodium hypochlorite solution in
water (7.4 g, 12 mmol) in one portion. The reaction flask was
located in the cleaner bath, where the surface of reactants was
slightly lower than the level of the water. The mixture was
irradiated 4 h (the reaction was monitored by TLC), during
which the pH was maintained at 12.0 by titrating with 0.1
mol/L NaOH. The reaction mixture was extracted with
dichloromethane (3 × 15 mL). The aqueous phase was acidified
to pH = 2 with 2 M HCl and was left overnight in the ice bath.
Adipic acid crystals was obtained, filtered and recrystallized
from water to obtain 270 mg, 94 %, m.p.: 152-153 ºC.
Sodium hypochlorite also is a common oxidizing and
chlorinating agent in various organic syntheses. Its solution is
attractive as industrial oxidants, being cheap and containing a
high percentage of available oxygen. Moreover, the salt
solutions resulting from the reactions, are relatively harmless
to the environment and can be electrolyticalty recycled14.
Ultrasound has increasingly been used in organic synthesis
in the last four decades. A large number of organic reactions
can be carried out in higher yields, shorter reaction time or
milder conditions under ultrasound irradiation. Rothenberg and
Lin, Zhi-Ping
