2-Chloropyridine

Preparation

:[[File:simple chlorination.png|500px|]] 2-Chloropyridine is produced by direct reaction of pyridine with chlorine. The initially formed 2-chloropyridine reacts further to give 2,6-dichloropyridine.

Alternatively, 2-chloropyridines can be conveniently synthesized in high yields from pyridine-N-oxides.

2-Chloropyridine was originally prepared by the chlorination of 2-hydroxypyridine with phosphoryl chloride.

Main reactions and applications

2-Chloropyridine undergoes substitution at the C-Cl bond.{{cite journal |author=Kevin W. C. Poon, Philip A. Albiniak, Gregory B. Dudley

Some commercial products include pyrithione, pyripropoxyfen, chlorphenamine, and disopyramide. In these conversions, chloride is displaced. The antihistamine pheniramine may be generated via the reaction of phenylacetonitrile with 2-chloropyridine in the presence of a base.

Environmental properties

Although pyridine is an excellent source of carbon, nitrogen, and energy for certain microorganisms, introduction of a halogen moiety significantly retards degradation of the pyridine ring. With the exception of 4-chloropyridine, each of the mono- and di-substituted chloropyridines were found to be relatively resistant to microbiological degradation in soil or liquid media. Estimated time for complete degradation was 30 days. 2-Chloropyridine exhibits extensive volatilization losses from water, less so when present in soil.

Toxicity

The is 64 mg/kg (dermal, rabbit).

References

References

1. (1960). "Notes- Dissociation Constants of 2-Substituted Pyridines". The Journal of Organic Chemistry.
2. (2007). "Pyridine and Pyridine Derivatives".
3. (2004). "Facile and Selective Synthesis of Chloromethylpyridines and Chloropyridines Using Diphosgene/Triphosgene". Synthetic Communications.
4. (1891). "Ueber das α-Pyridon (α-Oxypyridin)". Berichte der Deutschen Chemischen Gesellschaft.
5. Patrick M. Pollock, Kevin P. Cole. (2012). "t-Butyl as a Pyrazole Protecting Group: Preparation and Use of 1-tert-Butyl-3-Methyl-1H-Pyrazole-5-Amine". Organic Syntheses.
6. Pyrithione, the conjugate base of 2-mercaptopyridine-''N''-oxide, is a fungicide found in some shampoos. Oxidation 2-chloropyridine gives 2-chloropyridine-''N''-oxide.Cheng, Hefeng; She, Ji. 14. Improved preparation of 2-mercaptopyridine-''N''-oxide. Zhongguo Yiyao Gongye Zazhi. 1990, 21, (2), pp. 55-56. {{ISSN. 1001-8255
7. (1994). "New Synthetic Route to Pheniramines via Hydroformylation of Functionalyzed Olefins". The Journal of Organic Chemistry.
8. Sims, G. K. and L.E. Sommers. 1986. Biodegradation of pyridine derivatives in soil suspensions. Environmental Toxicology and Chemistry. 5:503-509.
9. Sims, G. K. and L.E. Sommers. 1985. Degradation of pyridine derivatives in soil. Journal of Environmental Quality. 14:580-584.