Introduction edit
.png)
| |
| Names | |
|---|---|
| IUPAC name
pentachloronitrobenzene
| |
| Other names
PCNB, quintozene
| |
| Identifiers | |
| UNII | |
| Properties | |
| C6Cl5NO2 | |
| Molar mass | 295.36 g/mol |
| Appearance | off white or yellow crystals |
| Density | 0.44 mg/L, slightly soluble in alcohols |
| Melting point | 144 |
| Boiling point | 328 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |
Pentachloronitrobenzene is a registered fungicide formally derived from nitrobenzene. It is either an off-white or yellow crystal, depending on its purity, with a musty odor.
Preparation edit
Pentachloronitrobenzene was originally synthesized in a laboratory in 1868. It was introduced to the agricultural world in the 1930s in Germany by Bayer AG as a substitute to mercurial pesticides. Pentachloronitrobenzene is prepared by chlorination of nitrobenzene at 60 – 70 ◦C in chlorosulfuric acid, with iodine as a catalyst. It can also be produced by the nitration of chlorinated benzenes.1 A side product of the synthesis of PCNB is hexachlorobenzene (HCB), which is considered equally as hazardous as PCNB[1]
- 1. 5 Cl2 + C2H5NO2 → C6Cl5NO2 + 5 HCl
Main Reactions edit
Reaction with ethanol – potassium hydroxide yields pentachlorophenetole, exemplifying an easy route to pentachlorophenyl ethers.[2]
- 2. C6Cl5NO2 + KOCH2CCH3 → C6Cl5OCH2CH3 + KNO2
Although PCNB has a very stable shelf life, it is labile in soil, with a half life of 1.8 days. It degrades to other metabolites, mainly reducing to pentachloroaniline (PCA), but also to pentachlorophenol (PCP) through hydrolysis and pentachlorothioanisole (PCTA). There is little information known about the degradation mechanisms.[3][4]
- 3. C6Cl5NO2 + 6 [H] → C6Cl5NH2 + 2 H2O
- 4. C6Cl5NO2 + 6 H2O → C6Cl5OH + HNO2
Applications edit
PCNB is used as a fungicide to suppress the growth of fungi in various crops, such as cotton, rice, and seed grains. It is also used to prevent the formation of slime in industrial waters. In 1989, usage of the compound was banned in the United States because of its persistence in the environment. In April 1993, PCNB became a federal hazardous air pollutant and was identified as a toxic air contaminant.[5] PCNB is still used widely in other countries as a fungicide, such as China and Japan. Residual amounts of the compound and its metabolites are still found in crops today. The degradation products, PCA and PCTA have been found in farming soils and in river sediments.[6]
References edit
- ^ Cairns; et al. (1987). "Identification of Several New Metabolites from Pentachloronitrobenzene by Gas Chromotagraphy/Mass Spectrometry". J. Agric Food Chem.: 433–439. doi:10.1021/jf00075a037.
{{cite journal}}: Explicit use of et al. in:|author=(help) - ^ Booth, G. Nitro Compunds, Aromatic, Ullmann's Encyclopedia of Industrial Chemistry, electronic release 7th ed.; Wiley-VCH,Weinheim, 2000. ISBN 978-3-527-31965-7
- ^ Sung-Kyu Shin; et al. (2003). "Isolation and Identification of a Pentachloronitrobenzene(PCNB) Degrading bacterium Alcaligenes xylosoxidans PCNB-2 from Agricultural Soil". The Journal of Microbiology: 165–168.
{{cite journal}}: Explicit use of et al. in:|author=(help) - ^ Tonghua Sun; et al. (2006). "Determination of 17 kinds of Banned Organochlorine Pestides in Water by Activated Carbon Fiber-Solid Phase Microextraction Coupled with GC-MS". Anal. Sci: 293. ISSN 0910-6340.
{{cite journal}}: Explicit use of et al. in:|author=(help) - ^ Howard, P. H. Handbook of Environmental Fate and Exposure Data for Organic Chemicals: Pesticides , CRC Press, 1991; pp. 551-553. ISBN 0873713281, 9780873713283
- ^ Sullivan, J. B.; Krieger, G. R. Clinical Environmental Health and Toxic Exposures, 2nd ed.; Lippincott Williams & Wilkins: Philadelphia, PA, 2001; pp. 1111-1112. ISBN 068308027X, 9780683080278