Rearrangement reaction of the hydroxyl group of α-hydroxyalkyltriphenyl phosphonium bromides

Abstract

No molecular ion peak from the Electron Impact Ionization of eight ω-hydroxyalkyltriphenyl phosphonium bromides (Ph3P+(CH2) OHBr, n=2–6, 8–10) can be found, except a part of some relative powerful fragment ions can be observed only. Each compound forms a very characteristic ion (O = PPh3 - 1)+ at m/z 277 through hydroxyl rearrangement reaction. The intensity of this ion is closely related with the size of the carbon chain of hydroxyalkyl and with temperature of ion source and temperature of sample probe. The above rearrangement reaction and the reaction to form ion at m/z 262 take place simultaneously, thus leading to strong competition. At n = 2, km at m/z 277 is the most powerful and becomes continuously the base peak. At n = 3 and n = 4, the intensity of ion at m/z 262 reaches the maximum, and is always the base peak, and the relative abundance of m/z 277 is only around 2% At n = 5, 6, 8, 9, 10, m/z 277 becomes base peak when the temperature of probe is below 300°. But, when the temperature increases from 300°C to 35oC, m/z 262 suddenly becomes the base peak, which is not in direct proportional relation with the size of carbon chain. It is proved by MIKES and accurate mass mat ion at m/z 277 produces a fragment ion (O = PPh2 - 2) + at m/z 199 with the loss of the neutral benzene molecule.