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Photolysis of Diborane at 1849 Å

Kreye, W. C. and Marcus, R. A. (1962) Photolysis of Diborane at 1849 Å. Journal of Chemical Physics, 37 (2). pp. 419-427. ISSN 0021-9606. doi:10.1063/1.1701337.

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The photolysis of diborane at 1849 Å has been studied in a specially constructed, internal‐type mercury‐vapor lamp. The products have been found to be H_2, B_(4)H_(10), B_(5)H_(11), and, at low pressures, a —BH— polymer. Reaction orders at 4°C have been obtained from linear plots of reaction products vs time for a range of diborane pressures from 0.08 to 80 cm, and at two light intensities. Linear relations between products and time existed only at very low conversions (∼1%), which required the development of a low‐temperature separation method for manipulating and analyzing the traces of B_(4)H_(10) and B_(5)H_(11). Because of the reactivity of these compounds, a detailed conditioning procedure was employed for the glass system. A mechanism consistant with the kinetic data and suggested by the kinetic results of thermal and photosensitized decomposition of diborane is postulated: the B_(5)H_(11) is assumed to be formed from a dissociation of B_(2)H_6 into BH_3's, the latter arising from an excited molecule. The B_(4)H_(10) and polymer are assumed to be formed from a dissociation of B_(2)H_6 into B_(2)H_5 and H, followed by radical recombination. There is a significant difference between the kinetics of thermal and photochemical B_(5)H_(11) formation, a result which may be due to the considerable energy excess of the 1849 quantum over that needed for dissociation (∼125‐kcal excess). These kinetic results raise a number of interesting questions, questions which can only be resolved through further investigations of effects due to light intensity, added inert gases, and temperature. The primary quantum yield of the step forming B_(2)H_5 and H is about 10 times higher than that of the one forming BH_3's. A rather rough estimate suggests that the former is of the order of magnitude of unity.

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Marcus, R. A.0000-0001-6547-1469
Additional Information:© 1962 American Institute of Physics. Received 24 November 1961. Taken from part of a thesis submitted by Warren C. Kreye in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Polytechnic Institute of Brooklyn, June 1960. Presented in part at the 134th American Chemical Society meeting (1958). The investigation reported herein was supported in part by the U. S. Office of Naval Research and by U. S. Air Force monitored by the Air Force Office of Scientific Research of the Air Research and Development Command.
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Office of Naval ResearchUNSPECIFIED
Air Force Office of Scientific Research (AFOSR)UNSPECIFIED
Air Research and Development CommandUNSPECIFIED
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Official Citation:Photolysis of Diborane at 1849 [A-ring] W. C. Kreye and R. A. Marcus, J. Chem. Phys. 37, 419 (1962), DOI:10.1063/1.1701337
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:34260
Deposited On:20 Sep 2012 21:41
Last Modified:09 Nov 2021 23:07

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