What is the product obtained when methyl vinyl ketone is reacted with 1,2-ethanedithiol and the product is further hydrogenated with Raney Nickel?
The answer could be 3 or 4.
1,2-ethanedithiol will react with the carbonyl group to form a dithiane (similar to the ethylene glycol reaction). Reaction of this with Raney Nickel/H2 desulfurises it, so the whole process is effectively a reduction of the carbonyl group to CH2. It depends on the reaction conditions whether the double bond survives. Raney Nickel can reduce alkenes.
You can read more about it here 1 and here 2