The ion-molecule reactions in propane and in methane–propane mixtures have been studied using an ion-trapping technique and rate coefficients have been measured for the reactions occurring. In pure propane the C2H5+ primary ions react by H− transfer to form C3H7+ whereas C2H4+ reacts to form C3H6+ (25%) and C3H7+ (75%). Using isotopically labelled propanes it was found that both n-propyl and i-propyl ions were formed with the n-propyl ions reacting slowly to produce i-propyl ions. In various deuterium labelled methane–propane mixtures C(H,D)5+ reacts with the propane with a rate constant of ∼1.5 × 10−9 cm3 molecule−1 s−1 in agreement with the calculated collision rate. It is shown that no hydrogens from the CH5+ ion are incorporated in the product ions which are found to be C2H5+ (70%), (CH3)2CH+ (25%), and CH3CH2CH2+ (5%).

No abstract