Chloranil: an important intermediate
Chloranil (2,3,5,6-tetrachloro-2,5-cyclohexadiene-1,4-dione), is extensively used as a fungicide, is an intermediate in the synthesis of medicines and pesticides, and is an oxidizing agent used in organic synthesis, particularly for dye intermediates, in China. The annual production of chloranil in recent years, in China, has been about 2000 tonnes. Chloranil is known for its strong oxidizing properties. It can cause oxidative stress and damage to cells by interacting with cysteine residues of some proteins[1-3].
p-Chloranil is used as a dye intermediate, oxidizing agent, vulcanizing agent and dehydrogenation reagent. It is also used to make chloranil electrodes for pH measurements. Further, it serves as a hydrogen acceptor and used for the aromatization reactions such as conversion of cyclohexadienes to the benzene derivatives. It is used to test the secondary amine. In addition to this, it is employed as a precursor to prepare diaziquone, which is used as a cancer chemotherapeutic agent.
Tetrachloro-1,4-benzoquinone is a potential intermediate in the process of pentachlorophenol-induced carcinogenicity.
Agricultural fungicide, dye intermediate, reagent. manufacture of electrodes for pH measurement.
ChEBI: A member of the class of 1,4-benzoquiones that is 1,4-benzoquinone in which all four hydrogens are substituted by chlorines.
Yellow powder with a slight odor.
Chloranil is sensitive to excessive light and heat. Chloranil is incompatible with strong oxidizing agents. Chloranil reacts with alkalis.
Flash point data for Chloranil are not available; however, Chloranil is probably combustible.
Three important chloranil manufacturing sites, the Ody Chemical Plant, Qsd Chemical Plant and Yueh Chemical Plant were selected as typical chloranil producers. Three chloranil product samples were collected, one from each plant, and stored at -20 ℃ before analysis. The different uses of chloranil can lead to distinct differences in the quality and purity of the chloranil produced. Sample Ch1 was made by the Ody Chemical Plant for use as an intermediate in pharmaceutical products such as diuretics and antisterone. It was extracted and purified using a recrystallization process to form a product with 99% purity. However, sample Ch3, produced by Yueh Chemical Plant, is not further purified as it is mainly used as a dye and pesticide intermediate, so it has a purity of only 90%. The purity of sample Ch2, from Qsd Chemical Plant, is between that of Ch1 and Ch3, at 96%.
The production of chloranil involves two steps: first, phenol is used as the raw material and converted to hydroquinone; and second, the hydroquinone is converted to chloranil in the presence of chlorine or hydrogen peroxide and hydrochloric acid[2].
Crystallise p-chloranil from acetic acid, acetone, *benzene, EtOH or toluene, dry it in a vacuum over P2O5, or from acetic acid and drying over NaOH in a vacuum desiccator. It can be sublimed under vacuum at 290o. A sample may contain significant amounts of the o-chloranil isomer as impurity. Purify it by triple sublimation under vacuum and recrystallise before use. It is a skin and mucous membrane irritant. [UV: Pummerer et al. Chem Ber 85 545 1952, Brook J Chem Soc 5040 1952, Beilstein 7 IV 2083.]
[1] Wenbin Liu. “Contamination and emission factors of PCDD/Fs, unintentional PCBs, HxCBz, PeCBz and polychlorophenols in chloranil in China.” Chemosphere 86 3 (2012): 248–51.
[2] Kaleru Mogilaiah, Boda Sakram, Janapatla Uma Rani. “Synthesis of 1,2,4-Triazolo[4,3-a][1,8]naphthyridines Using Chloranil under Microwave Irradiation.” ChemInform 37 2 (2005).
[3] Weibing Zhang . “The metabolic activation of pentachlorophenol to chloranil as a potent inhibitor of human and rat placental 3β-hydroxysteroid dehydrogenases.” Toxicology letters 395 (2024): Pages 40-49.
