Which of the following would be the most appropriate S\({}{\rm N}\)2 [S- N- two] leaving group?

W) Hydroxyl

X) O-Trifluoromethanesulfonate [try-FLOOR-oh-METH-ayn-SUHL-fuh-nayt]

Y) O-Ethyl

Z) O-Acyl
X) O-TRIFLUOROMETHANESULFORNATE