3-Chloropyridine is an

aryl chloride In organic chemistry, an aryl halide (also known as a haloarene) is an aromatic compound in which one or more hydrogen atoms directly bonded to an aromatic ring are replaced by a halide ion (such as fluorine F''−'', chlorine Cl−1,−3,−5, bro ...

and isomer of

chloropyridine Chloropyridines are a group of aryl chlorides consisting of a pyridine ring with chlorine atoms as substituents. Chloropyridines include: *2-Chloropyridine * 3-Chloropyridine * 4-Chloropyridine * 2,6-Dichloropyridine Production Direct halogenation ...

with the formula C₅H₄ClN. It is a colorless liquid that is mainly used as a building block in organic synthesis. The compound is a substrate for many coupling processes including the

Heck reaction The Heck reaction (also called the Mizoroki–Heck reaction) is the chemical reaction of an unsaturated halide (or triflate) with an alkene in the presence of a base and a palladium catalyst to form a substituted alkene. It is named after T ...

Suzuki reaction The Suzuki reaction or Suzuki coupling is an organic reaction that uses a palladium complex catalyst to cross-couple a boronic acid to an organohalide. It was first published in 1979 by Akira Suzuki, and he shared the 2010 Nobel Prize in Chemi ...

, and

Ullmann reaction The Ullmann reaction or Ullmann coupling, named after Fritz Ullmann, couples two aryl or alkyl groups with the help of copper. The reaction was first reported by Ullmann and his student Bielecki in 1901. It has been later shown that palladium and ...

Preparation

3-Chloropyridine may be prepared by the direct chlorination of

pyridine Pyridine is a basic (chemistry), basic heterocyclic compound, heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom . It is a highly flammable, weak ...

with

aluminium chloride Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms a hexahydrate with the formula , containing six water molecules of hydration. Both the anhydrous form and the hexahydrate are col ...

used as the catalyst. The yield is 33%. A less expensive way of preparing 3-chloropyridine consists of the gas phase pyrolysis of a mixture of

pyrrole Pyrrole is a heterocyclic, aromatic, organic compound, a five-membered ring with the formula . It is a colorless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., ''N''-methylpyrrol ...

and

chloroform Chloroform, or trichloromethane (often abbreviated as TCM), is an organochloride with the formula and a common solvent. It is a volatile, colorless, sweet-smelling, dense liquid produced on a large scale as a precursor to refrigerants and po ...

in an empty glass tube. The molar ratio of the reagents is one to five. The yields range from 25 to 33%. A little

2-chloropyridine 2-Chloropyridine is an aryl chloride with the formula C5H4ClN. It is a colorless liquid that is mainly used to generate fungicides and insecticides in industry. It also serves to generate antihistamines and antiarrythymics for pharmaceutical purpo ...

is formed as a side product. The process is thought to be an example of the

Ciamician–Dennstedt rearrangement Pyridine is a basic (chemistry), basic heterocyclic compound, heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom . It is a highly flammable, weak ...

. :

3-Chloropyridine synthesis via pyrolysis

References

{{DEFAULTSORT:Chloropyridine, 3- Chloropyridines 3-Pyridyl compounds