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Q.
When acetylene is passed into methanol at $160- 200ºC$ in the presence of a small amount of potassium methoxide under pressure, the following is formed -
When acetylene is passed into methanol at $160-200^ºC$ in the presence of a small amount $(1-2\%)$ of potassium methoxide and under pressure just high enough to prevent boiling, methyl vinyl ether is formed.
The mechanism is believed to involve nucleophildic attack in the first step.
$\ce{HC$\equiv$ CH + CH3 O^-->C^-H=CH OCH3->[CH_3OH]CH2=}$ $\underset{\text{Methyl vinyl ether}}{\ce{CHO CH3 + CH3O¯}}$