In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

The Zeisel test can be used to detect them, and the compound THF is a very polar example of one. The "crown" varieties are cyclic and can be used as solvents in Grignard reagents due to their low reactivity. These compounds can be produced by the Williamson synthesis or by the dehydration of alcohols. For 10 points, identify these chemical compounds, characterized by two alkyl groups single bonded to an oxygen, whose diethyl version used to be used as an anesthetic.
Science