Kinetics of Two Exchange Reactions Involving Diborane

The kinetics of the exchange between deuterium and diborane were studied over a temperature range of 25°—75°C, and it was found that the reaction was $\frac{3}{2}$ order with respect to diborane and zero order with respect to deuterium at high pressures. At low pressures the zero‐order dependence of the deuterium changed to first‐order. The activation energy of the zero‐order reaction was 20.4±2 kcal/mole. A mechanism is proposed in which the borine radical reacts with deuterium on the wall and is followed by a rate determining bimolecular collision between the partially deuterated borine radical and a diborane molecule. The closely related exchange reaction between normal and completely deuterated diborane was also investigated. The total order of this reaction was $\frac{3}{2}$ , and it had an activation energy of 21.8±3 kcal/mole. A mechanism is proposed which involves the collision between a borine radical and a diborane molecule as the rate determining step.