What is the main product when an excess of ethyl alcohol vapour is passed over heated alumina at 250 °C?
I read that this reaction gives an ether (here, diethyl ether) at relatively lower temperature than when it gives an alkene (here, ethene). This didn't bother me much as I had also read that higher temperatures favour elimination reactions, whereas lower temperatures favour nucleophilic substitutions.
So I was pretty sure that at 250 °C it would give ethene. But according to the book, it's diethyl ether. Why does this happen?
One thought that I had was maybe it's because “excess of ethyl alcohol” is mentioned, it would follow the formation of ether by the reaction of two alcohol molecules. Is that right?