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I was solving questions from aldehyde, ketones and ethers and I came across a question that asks:

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What is the product obtained when Methyl vinyl ketone is reacted with 1,2-Ethanedithiol and the product is further hydrogenated with Raney Nickel?

My thoughts:

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I thought that the reaction could be similar to the one where we react a ketone with ethylene glycol, then on further hydrogenation the double bond breaks. I may be wrong. Any help will be highly appreciated

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    $\begingroup$ Also, do note that it is Raney nickel, not "Rancy" nickel. $\endgroup$ Nov 22 '20 at 12:14
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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

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    $\begingroup$ In the presence of Ni(R)/H2 I would expect desulfurization and double bond reduction, i.e., n-butane. In the presence of degassed Ni(R), the double bond may survive. However, because the desulfurization is likely radical in nature, 2-butenes in addition to 1-butene would be expected. Your thoughts? $\endgroup$
    – user55119
    Nov 22 '20 at 15:42
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    $\begingroup$ I have modified my answer. Just stirring in EtOH with Raney Ni can desulfurize some of these. I think this is a poor example to teach this reaction with as there are these other possibilities . I suspect this was set without thinking too hard about it, or reference to the literature. $\endgroup$
    – Waylander
    Nov 22 '20 at 16:00
  • $\begingroup$ I agree. This type of question does a disservice to the facts. $\endgroup$
    – user55119
    Nov 22 '20 at 16:01

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