Correct option is D
The Chugaev elimination is a chemical reaction that involves the elimination of water from alcohols to produce alkenes. The intermediate is a xanthate.
In the first step, a xanthate salt is formed out of the alkoxide and carbon disulfide (CS2). With the addition of iodomethane, the alkoxide is transformed into a methyl xanthate.
At about 200 °C, the alkene is formed by an intramolecular elimination. In a 6-membered cyclic transition state the hydrogen atom is removed from the carbon atom β to the xanthate oxygen in a syn-elimination. The side product decomposes to carbonyl sulfide (OCS) and methanethiol.
