Thionyl Chloride - A Versatile Reagent

Introduction

Thionyl chloride exhibits several features which have made it particularly attractive as a reagent in organic ­synthesis. It is often applied as a powerful chlorinating ­reagent, and reacts as such with carbonyl compounds, ­aromatic sulfochlorides, and aliphatic alcohols; the formed intermediates can be further transformed to other useful compounds. [1] It can also be used as an HCl pre­cursor and reacts in electrophilic additions or substitutions with compounds containing C-C multiple bonds. Thionyl chloride also reacts with amines or imines to form sulfinyl chlorides and it reacts with active methyl or active ­methylene compounds to form sulfenyl chlorides through Pummerer-type rearrangement. [2] In addition, it can also be used as a chlorinating reagent through its oxidation and partial dehydrogenation of organic compounds to give sulfuryl chloride. In some reactions it serves as con­densing reagent to form heterocyclic compounds, or it can be used as catalyst.

In industrial production, thionyl chloride is used for the synthesis of carboxylic acid chlorides. These products are frequently used as intermediates for the production of pharmaceutical active ingredients, crop protection ­reagents, and dyestuffs.

Compared with other chlorinating reagents, thionyl ­chloride has many advantages: The end product is easy to isolate, it is comparatively easy to handle, and the yields are generally high. It is miscible with nearly all organic solvents and is itself a good solvent for most organic ­compounds.

References

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