Highly carcinogenic bis-chloromethyl byproducts containing (-5[1])this functional group limit industrial use of the Blanc chloromethylation. Potassium iodide can be used to test for explosive peroxides (10[1])in stocks of compounds with this group that have been exposed to air. (10[1])Cryptands are 3D analogues of a cyclic version of these (10[1])groups useful for complexing alkali metals (10[1])and for acting as phase transfer (10[1])catalysts. This group’s ability to complex (10[1])Mg2+ ions and general non-reactivity (10[1])allows molecules with this group to be used to store Grignard reagents. (-5[1])Cyclic (10[2])molecules (10[1])containing this group include furans (10[1]-5[1])and molecules (10[1])named after crowns. (10[2])For 10 (10[1])points, (10[1])name this functional (10[1])group (10[1])consisting of an oxygen flanked by two R groups, whose diethyl variety can be used as an anesthetic. ■END■ (10[5]0[1])