An abinitio and ion cyclotron resonance study of the protonation of borazine

1979 ◽  
Vol 57 (14) ◽  
pp. 1751-1757 ◽  
Author(s):  
C. E. Doiron ◽  
F. Grein ◽  
T. B. McMahon ◽  
K. Vasudevan
Keyword(s):  
Ab Initio ◽  
Proton Affinity ◽  
Cyclotron Resonance ◽  
Molecular Ions ◽  
Ion Cyclotron Resonance ◽  
Molecule Reaction ◽  
Ion Molecule Reactions ◽  
Ion Cyclotron ◽  
Gas Phase Ion ◽  
Protonated Nitrogen Atom

The gas phase ion–molecule reactions and proton affinity of borazine have been investigated by both theoretical ab initio and ion cyclotron resonance techniques. The experimental proton affinity has been determined from competitive proton transfer equilibria with standard reference bases and found to be 196.4 ± 0.2 kcal/mol. Ion–molecule reaction schemes for reaction of borazine molecular ions have been proposed. Ab initio calculations find the proton affinity of borazine to be 203.4 kcal/mol and the most energetically favorable structure of the borazinium ion is one in which very little structural change occurs relative to neutral borazine with the exception of the geometry about the protonated nitrogen atom. Charge distributions and bond lengths are used to explain bonding changes upon protonation.

Thermodynamic control in the reactions of gas phase anions. An abinitio and ion cyclotron resonance study of the reactions of anions with diborane

1985 ◽  
Vol 63 (2) ◽  
pp. 281-287 ◽  
Author(s):  
O. Elsenstein ◽  
M. Kayser ◽  
M. Roy ◽  
T. B. McMahon
Keyword(s):  
Gas Phase ◽  
Cyclotron Resonance ◽  
Reaction Pathway ◽  
Basis Set ◽  
Resonance Spectroscopy ◽  
Ion Cyclotron Resonance ◽  
Ion Molecule Reactions ◽  
Ion Cyclotron ◽  
Reaction Channels ◽  
Gas Phase Ion

The gas phase ion molecule reactions of a number of anions, X−, with diborane, B2H6 have been investigated using ion cyclotron resonance spectroscopy. Two distinct reaction channels are observed in addition to simple proton transfer. The first of these is production of BH4− and BH2X while the second is formation of BH3X− and BH3. In order to determine the importance of thermodynamic factors in the course of reaction abinitio calculations have been carried out on the species involved to obtain the relative stabilities of the two possible pairs of products. The 4-31 +G basis set incorporating additional flat s and p functions has been used since this basis set has been demonstrated to give the most accurate description of anions to date. The results obtained indicate that the thermochemical factors are instrumental in determining the reaction pathway.

Bimolecular production of gas phase ionic hydrates by ion cyclotron resonance spectroscopy

1980 ◽  
Vol 58 (8) ◽  
pp. 863-865 ◽  
Author(s):  
R. L. Clair ◽  
T. B. McMahon
Keyword(s):  
Gas Phase ◽  
Cyclotron Resonance ◽  
Resonance Spectroscopy ◽  
Ion Cyclotron Resonance ◽  
Ion Chemistry ◽  
Ion Molecule Reactions ◽  
Hydronium Ion ◽  
Dominant Feature ◽  
Ion Cyclotron ◽  
Gas Phase Ion

The gas phase ion–molecule reactions of α,α,α′,α′ tetrafluorodimethyl ether both alone and in mixtures with water have been examined. The dominant feature of the ion chemistry of these mixtures is the sequential bimolecular production of the hydrated hydronium ion, H5O2+. Two independent mechanistic pathways for production of H5O2+ are outlined arising from reaction of H3O+ with (CF2H)2O and from CF2H—O=CHF+ with H2O. Implications for examination of solvent switching equilibria are discussed.

scholarly journals Bimolecular production of proton bound dimers in the gas phase. A low pressure ion cyclotron resonance technique for examination of solvent exchange equilibria and determination of single molecule solvation energetics

1982 ◽  
Vol 60 (4) ◽  
pp. 542-544 ◽  
Author(s):  
J. W. Larson ◽  
R. L. Clair ◽  
T. B. McMahon
Keyword(s):  
Gas Phase ◽  
Single Molecule ◽  
Cyclotron Resonance ◽  
Ion Cyclotron Resonance ◽  
Solvent Exchange ◽  
Ion Molecule Reactions ◽  
Ion Cyclotron ◽  
Gas Phase Ion ◽  
Low Pressures

A scheme is presented whereby sequences of fast bimolecular gas phase ion molecule reactions in mixtures containing (CHF2)2O may be used to generate proton bound dimer species at low pressures in an ion cyclotron resonance spectrometer. Using competitive solvent switching reactions it is demonstrated that solvent exchange equilibria may be readily established and from the thermochemical data derived from such equilibria accurate relative single molecule solvation energetics obtained.

Gas phase acidic solvolysis reactions of acyl halides by ion cyclotron resonance spectroscopy

1978 ◽  
Vol 56 (5) ◽  
pp. 670-679 ◽  
Author(s):  
T. B. McMahon
Keyword(s):  
Gas Phase ◽  
Cyclotron Resonance ◽  
Resonance Spectroscopy ◽  
Ion Cyclotron Resonance ◽  
Elimination Reaction ◽  
Ion Molecule Reactions ◽  
Ion Cyclotron ◽  
Process Observation ◽  
Gas Phase Ion ◽  
Acyl Halides

A number of gas phase ion molecule reactions of protonated species with acyl halides have been examined by ion cyclotron resonance spectroscopy. A number of these reactions are found to involve an addition–elimination reaction having the character of an acidic solvolysis process. Observation of the occurrence or non-occurrence of such reactions and a consideration of appropriate thermochemical data allow a set of criteria to be formulated governing the feasibility of observing the acidic solvolysis reaction. In addition a number of mechanistic inferences are made concerning intermediates involved in the various reactions.

Time-resolved ion cyclotron resonance

1978 ◽  
Vol 364 (1718) ◽  
pp. 367-381 ◽  
Keyword(s):  
Cyclotron Resonance ◽  
Low Energy ◽  
Interstellar Space ◽  
Ion Cyclotron Resonance ◽  
Absolute Rate ◽  
Time Resolved ◽  
Ion Molecule Reactions ◽  
Quadrupole Trap ◽  
Ion Cyclotron ◽  
Improved Technique

Ion cyclotron resonance (i. c. r.) is a technique for the study of ion-molecule reactions in the collisional range from thermal to several electron volts. The study of these reactions at low energy has been given impetus by the discovery of their importance in the ionosphere and in interstellar space. This communication identifies some possible weaknesses inherent in current i. c. r. work and suggests an improved technique with which it is possible to determine absolute rate constants more reliably. As an illustration of the technique a measurement of the rate constant for the reaction CH 4 + + CH 4 → k CH 5 + + CH 3 is presented. This value is k = 1.21 ± 0.09 × 10 -15 m 3 s -1 . A new i. c. r. cell design is discussed with which it is hoped to provide further improvement in reliability by the production of a homogeneous radiofrequency field within a true quadrupole trap.

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