Menthol Is Obtained from Oils of Peppermint and Spearmint and Is

Essay

Menthol is obtained from oils of peppermint and spearmint and is often added to cough drops to give a minty, cooling sensation. In the electron ionization mass spectrum of menthol, the molecular ion peak is not observed, but the largest fragment has an m/z 138 at 27% relative abundance and an ion at m/z 139 with a 3% relative abundance. Given the two possible compounds, identify which is menthol and explain how you arrived at that conclusion.