Kinetic energy release in thermal ion--molecule reactions: The Nb sup 2+ --(benzene) single charge--transfer reaction

Journal Article · Fri Mar 15 04:00:00 EST 1991 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.460614· OSTI ID:5715607

Gord, J R; Freiser, B S ^[1]; Buckner, S W ^[2]

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1. Herbert C. Brown Laboratory of Chemistry, Purdue University, West Lafayette, Indiana 47907 (USA)
2. Department of Chemistry, University of Arizona, Tucson, Arizona 85721 (USA)

We have adapted the techniques originally developed to measure ion kinetic energies in ion cyclotron resonance (ICR) spectrometry to study the single charge--transfer reaction of Nb{sup 2+} with benzene under thermal conditions in a Fourier transform ion cyclotron resonance mass spectrometer (FTICRMS). The partitioning of reaction exothermicity among the internal and translational modes available is consistent with a long-distance electron-transfer mechanism, in which the reactants approach on an ion-induced dipole attractive potential and cross to a repulsive potential at a critical separation of {similar to}7.5 A when electron transfer occurs. The reaction exothermicity, 5.08 eV, is partitioned to translation of Nb{sup +} , 0.81{plus minus}0.25 eV, translation of C{sub 6} H{sub 6}{sup +}, 1.22{plus minus}0.25 eV, and internal excitation of C{sub 6} H{sub 6}{sup +} to produce the la{sub 2{ital u}} electronic state, which is {similar to}3 eV above the ground state of the ion. We have also studied the kinetics of the reaction of Nb{sup 2+} with benzene and determined the rate constant, {ital k} = 1.4{times}10{sup {minus}9} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}, and the efficiency, 0.60, of the process. These also support the proposed charge--transfer mechanism. In addition to the charge--transfer pathway, which accounts for 95% of the reaction products, Nb{sup 2+} is observed to dehydrogenate benzene to form Nb{sup 2+} (benzyne). This process implies {ital D}(Nb{sup 2+} --benzyne){ge}79 kcal/mol.

• DOE Contract Number: FG02-87ER13766
• OSTI ID: 5715607
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 94:6; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
AROMATICS
ATOMIC IONS
BENZENE
CHARGE EXCHANGE
CHARGED PARTICLES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DEHYDROGENATION
ELECTRON TRANSFER
ENERGY
HYDROCARBONS
ION CYCLOTRON RESONANCE SPECTROSCOPY
ION SPECTROSCOPY
IONS
KINETIC ENERGY
KINETICS
NIOBIUM IONS
ORGANIC COMPOUNDS
REACTION KINETICS
SPECTROSCOPY