Polymers with this functional group are added to sorbitan and then esterified with a fatty acid to form Tween. These compounds are common headgroups for non-ionic detergents. Lipids modified with a polymer with this functional group coat drugs or mRNA in solid lipid nanoparticles, which are stabilized similarly to stealth liposomes. A group of (*) cyclic compounds containing this functional group are named systematically with two numbers, (10[1])the first of which is three times larger than the second. This non-alcohol functional group is repeated in PEG, a polymer of ethylene oxide whose repeating unit matches that of so-called ‘crown’ shaped compounds. (10[2])For 10 points, what functional groups feature an oxygen sandwiched by two carbons? ■END■ (0[2])