Question

Explain Darzen's process

Answer 1

Darzens Condensation may be described as the base induced condensation of aldehyde or ketone with a halogenomethylene substance to form an αα, ββ-epoxy ester (glycidic ester). The reaction was first discovered by Erlen-meyer. But, later it was developed by Darzens. Both aldehydes and ketones can be employed. But, the latter are less reactive.


Moreover, aliphatic aldehydes give poor yields for the obvious reason that they undergo aldol condensation. The halo-genomethylene substances must contain an αα-hydrogen atom. A number of bases have been employed but potassium tert-butoxide has proved to be the most efficient condensing agent. The reaction is usually carried out under nitrogen atmosphere and at low temperatures.

Darzens Reaction Mechanism

The activated methylene group of phenacyl chloride loses a proton to the base to form enolate ion.

SN2 attack on the carbonyl carbon of the aldehyde to give the chlorohydrin intermediate, followed by intramolecular displacement of the chloride ion.



The Darzens reaction is a well known reaction that enables the construction of highly functionalized oxiranes. Enantioselective Darzens condensation leading to chiral epoxiranes has also been achieve.

Answer 2

Explanation:

When a Alkyl alcohol reacts with Thionyl Chloride under the action Pyridine, haloalkane is produced with Hydrochloric gas as a by product.

It is called Darzens Reaction process.

Chemical Equation is in the attachment