Chugaev elimination

The Chugaev reaction ( also Chugaev reaction) is after the Moscow chemist Lev Alexandrovich Chugaev ( 1873-1922 ) named.

As Chugaev reaction or elimination is defined as the dehydration of primary alcohols to terminal alkenes. Total are cleaved from the hydroxy and an alcohol to an adjacent carbon, a hydrogen atom, a double bond between the adjacent carbon atoms is produced. As intermediates occur xanthates. The reaction was discovered in 1899, as Chugaev sought a milder alternative to dehydration by ester pyrolysis.

Overall reaction equation

Reaction mechanism

In the first step of the alkoxide and carbon disulfide (CS2 ) formed one xanthate, which with a iodoalkane - is converted to the thioester - mostly methyl iodide:

At about 200 ° C and then formed in a stereospecific syn-elimination alkene. In a six-membered cyclic transition state a hydrogen atom from the β - carbon atom is transferred to the sulfur. The by-product decays further to carbonyl sulfide and methanethiol:

Pyrolysis of other esters and analogous substances

A similar reaction to go other esters, such as urethane, carbonic acid and acetic acid ester or amine oxide ( Cope elimination ) a. The tendency of the pyrolysis decreases as follows:

Amine oxides can be from 80 to 160 ° C, xanthogenic at 120 to 200 ° C and carboxylic acid esters only at 400 to 500 ° C pyrolysis.

Swell

• Latscha, Hans P.: Chemical - based knowledge. Berlin ( 2002): Springer.
• Organikum, German VEB Verlag der Wissenschaften, Berlin 1976.