Reactions with electric-discharge induced

The construction of C—B bonds in carboranes is effected by reaction of aikynes with polyboron hydrides. High-T and electric discharge-induced reactions between these reagents yield close cage systems, whereas milder conditions can lead to nido-carboranes. The preferred route to the parent closo-l,6-C2B4Hg and -2,4-C2B5H7 compounds involves the direct thermal reaction (500-600°C) of pentaborane(9) and acetylene in a continuous-flow system. Also formed is the smallest known closo-carborane, 1,5-0263115, in which the combined yields of products approach 70% and the product distribution of 0265117 0264115 0263115 is ca. 5 5 1 ... 

Semenov and Rjabinin studied the oxidation of sulfur in a vessel containing solid sulfur at temperatures of 80-120 with O2 present at pressures under 20 torr. They found SO2 and SO3 as products, with the SO3 varying from 20 to 60 % of the total products. As in the case of phosphorus oxidation, the total pressure fell asymptotically to a minimum as the sulfur was oxidized. There was also a short induction period, the duration of which was temperature-dependent. Above a certain maximum and below a minimum value of sulfur pressure the oxidation was immeasurably slow. They concluded that either ozone or active S atoms initiated chain reactions by inducing the formation of chain carriers. Semenov and Rjabinin generally found no reaction between sulfur vapor and oxygen at 80-120° unless initiated by a pulsed electrical discharge. This reaction was accompanied by a luminescence, and its rate was almost independent of [O2] when this was below 1 torr, until the [O2] fell to about 0.2 torr, when the reaction ceased. The emission filled the vessel unless [O2] exceeded 20 torr, in which case it was confined to the surface of the sulfur. 

Pulsed electronic transition chemical laser operation appears to be possible in a much wider class of reaction systems than those defined by the foregoing considerations. Reaction initiation in premixed reagents by pulsed techniques can provide population inversions on time scales short compared with fluid mixing times and relaxation times for lower laser states. Such techniques include photolysis, laser-induced dissociation, electrical discharge production of atoms or metastables, and shock-induced dissociation and pyrolysis. Such lasers are subject to the pumping rate condition of Figure 3.21 which is much less restrictive than the condition for diffusive mixing... 

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