Question

how do you convert ethanoic acid to ethene

Answer 1

First, you need a strong reducing agent to turn it to ethanol; something like sodium borohydride should do the trick.
Next, you need something highly hygroscopic which sucks the moisture out of everything it touches, even when chemically bonded to it. Concentrated sulphuric acid fits the bill.

Answer 2

NaBH4 doesn't reduce carboxylic acids. you can use LiAlH4

Answer 3

Oops, my bad. Thanks for pointing that out.

Answer 4

it's all good. your reasoning is still sound.

Answer 5

Thanks. Nice of you to give me a medal even though I got it wrong.