| 2-Chloropyridine | |
|---|---|
| Identifiers | |
| CAS number | 109-09-1 |
| ChemSpider | 7689 |
| ChEBI | CHEBI:39174 |
| ChEMBL | CHEMBL509579 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C5H4ClN |
| Molar mass | 113.54 g/mol |
| Appearance | colorless, clear liquid |
| Melting point |
-46 °C, 227 K, -51 °F |
| Boiling point |
166 °C, 439 K, 331 °F |
| Solubility in water | 27 g/L |
| Acidity (pKa) | 0.49 [1] |
| Hazards | |
| MSDS | MSDS |
| R-phrases | R23 R38 |
| S-phrases | S26 S37 S39 S45 |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
2-Chloropyridine is an organohalide with the formula C5H4ClN. It is primarily used to generate fungicides and insecticides in industry. It also serves to generate antihistamines and antiarrythymics for pharmaceutical purposes.[2]
Contents |
2-Choropyridine was originally synthesized in 1898 by the chlorination of 2-hydroxypyridine.[3]
2-Chloropyridine can also be generated by halogenating pyridine. This reaction proceeds under heating by the direct chlorination of pyridine by molecular chlorine to afford a mixture of 2-chloropyridine and 2,6-dichloropyridine.[2]
Another synthesis is to chlorinate pyridinol with phosporyl chloride.[2]
Alternatively, 2-chloropyridines can be conveniently synthesized in high yields from pyridine-N-oxides.[4]
2-Chloropyridine reacts with nucleophiles to generate pyridine derivatives substituted at the second and fourth carbons on the heterocycle. Therefore, many reactions using 2-chloropyridine generate mixtures of products which require further workup to isolate the desired isomer.[2]
2-chloropyridine is primarily used to generate other pyridine derivatives. Some commercial products include pyrithione, pyripropoxyfen, chlorphenamine, and disopyramide. These reactions rely on chloride’s nature as a good leaving group to facilitate the transfer of a substrate onto the pyridine ring.[2] Pyrithione, the conjugate base of 2-mercaptopyridine-N-oxide, is a fungicide found in some shampoos. It is generated from 2-chloropyridine by reacting the N-oxide of 2-chloropyridine with Na2S in a basic solution, before adding aqueous HCl.[5] Used as an antihistamine, pheniramine may be generated via several different pathways. One synthesis is to hydroformylate functionalized olefins. This reaction proceeds by reacting phenylacetonitrile with 2-chloropyridine in the presence of a base. The resulting intermediate is then alkylated by 2-(dimethylamino)ethyl chloride and the cyano group removed.[6]
Though 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.[7] Estimated time for complete degradation was > 30 days. 2-Chloropyridine exhibits extensive volatilization losses from water, less so when present in soil.[8]