Difference between revisions of "Pentachloronitrobenzene"

Latest revision as of 10:04, 20 September 2010

Pentachloronitrobenzene
File:PCNB.png
IUPAC name pentachloronitrobenzene
Other names PCNB, quintozene
style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers
CAS number	82-68-8 Y
SMILES	Script error: No such module "collapsible list".
style="background: #F8EABA; text-align: center;" colspan="2" | Properties
Molecular formula	C6Cl5NO2
Molar mass	295.36 g/mol
Appearance	off-white or yellow crystals
Melting point	44 °C, 317 K, 111 °F
Boiling point	328 °C, decomposes
Solubility in water	0.44 mg/L
Solubility	slightly soluble in alcohols
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Pentachloronitrobenzene, typically abbreviated PCNB, is a registered fungicide formally derived from nitrobenzene. It is either an off-white or yellow solid, depending on its purity, with a musty odor.

Preparation

PCNB was originally synthesized in the laboratory in 1868. It was introduced to the agricultural world in the 1930s in Germany by Bayer AG as a substitute to mercurial pesticides. PCNB 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. A side product of the synthesis of PCNB is hexachlorobenzene (HCB), which is considered as hazardous as PCNB.^[1]

5 Cl₂ + C₂H₅NO₂ → C₆Cl₅NO₂ + 5 HCl

Main reactions

Reaction with ethanol and potassium hydroxide yields pentachlorophenetole, indicating its high reactivity:^[2]

C₆Cl₅NO₂ + KOCH₂CH₃ → C₆Cl₅OCH₂CH₃ + KNO₂

Although PCNB has a long shelflife, 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). Little information is available about the degradation mechanisms.^[3][4]

C₆Cl₅NO₂ + 6 [H] → C₆Cl₅NH₂ + 2 H₂O

C₆Cl₅NO₂ + 6 H₂O → C₆Cl₅OH + HNO₂

Applications

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 was declared a hazardous air pollutant in the U.S.^[5] PCNB is still used widely as a fungicide in other countries, 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

1. ↑ Cairns et. al; Siegmund, Emil G.; Krick, Fred (1987). "Identification of Several New Metabolites from Pentachloronitrobenzene by Gas Chromotagraphy/Mass Spectrometry". J. Agric Food Chem. 35: 433–439. doi:10.1021/jf00075a037. 
2. ↑ 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
3. ↑ 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. 
4. ↑ 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. doi:0910-6340 Check |doi= value (help). 
5. ↑ Howard, P. H. Handbook of Environmental Fate and Exposure Data for Organic Chemicals: Pesticides , CRC Press, 1991; pp. 551-553. ISBN 0873713281, 9780873713283
6. ↑ 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

ja:ペンタクロロニトロベンゼン pt:Pentacloronitrobenzeno