Dissociation and Ion-Molecule Reactions of Alkane Radical Cations. Time-Resolved FDMR

<div> <div> <div> <p>A key step in gas-phase polycyclic aromatic hydrocarbon (PAH) formation involves the addition of acetylene (or other alkyne) to σ-type aromatic radicals, with successive additions yielding more complex PAHs. A similar process can happen for N- containing aromatics. In cold diffuse environments, such as the interstellar medium, rates of radical addition may be enhanced when the σ-type radical is charged. This paper investigates the gas-phase ion-molecule reactions of acetylene with nine aromatic distonic σ-type radical cations derived from pyridinium (Pyr), anilinium (Anl) and benzonitrilium (Bzn) ions. Three isomers are studied in each case (radical sites at the ortho, meta and para positions). Using a room temperature ion trap, second-order rate coefficients, product branching ratios and reaction efficiencies are reported. </p> </div> </div> </div>

Download Full-text

Properties and Reactivity of First and Second Row Hydrides. IV. Interactions Between Hydrides and Their Radical Ions

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19930001 ◽

1993 ◽

Vol 58 (1) ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Rudolf Zahradník

Keyword(s):

Radical Cations ◽

Stabilization Energy ◽

Hydrogen Atom Abstraction ◽

Type Ii ◽

Radical Ions ◽

Reaction Products ◽

Ion Molecule Reactions ◽

Heats Of Reaction ◽

Experimental Values ◽

Easy Differentiation

The energies and heats of ion-molecule reactions have been calculated (MP4/6-31G**//6-31G** or better level) and compared with the experimental values obtained from the heats of formation. Two main types of reactions have been studied: (i) AHn + AHn+• ↔ AHn+1+ + AHn-1• (A = C to F and Si to Cl), (ii) AHn + BHm+• ↔ AHn+1+ + BHm-1• or AHn-1+• + BHm+1+ (A and B = C to F). In contrast to (i), processes of type (ii) permit easy differentiation between the proton transfer and hydrogen atom abstraction mechanisms. A third type of interaction involves reactions with radical anions (A = Li to F); comparison was made with analogous processes with radical cations. A brief comment is made about the influence of the level of computational sophistication on the energies and heats of reaction, as well as on the stabilization energy of a hydrogen bonded intermediate, a structure which is similar to that of the reaction products.

Download Full-text

Time-resolved ion cyclotron resonance

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1978.0206 ◽

1978 ◽

Vol 364 (1718) ◽

pp. 367-381 ◽

Cited By ~ 1

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.

Download Full-text

Time-Resolved Photodissociations of Iodotoluene Radical Cations†

The Journal of Physical Chemistry A ◽

10.1021/jp025703c ◽

2002 ◽

Vol 106 (42) ◽

pp. 9918-9924 ◽

Cited By ~ 12

Author(s):

Byungjoo Kim ◽

Seung Koo Shin

Keyword(s):

Radical Cations ◽

Time Resolved

Download Full-text

Investigation of Carotenoid Radical Cations and Triplet States by Laser Flash Photolysis and Time-Resolved Resonance Raman Spectroscopy: Observation of Competitive Energy and Electron Transfer

Journal of the American Chemical Society ◽

10.1021/ja953181r ◽

1996 ◽

Vol 118 (7) ◽

pp. 1756-1761 ◽

Cited By ~ 44

Author(s):

J. H. Tinkler ◽

S. M. Tavender ◽

A. W. Parker ◽

D. J. McGarvey ◽

L. Mulroy ◽

...

Keyword(s):

Raman Spectroscopy ◽

Flash Photolysis ◽

Laser Flash Photolysis ◽

Resonance Raman Spectroscopy ◽

Radical Cations ◽

Laser Flash ◽

Triplet States ◽

Time Resolved ◽

Energy And Electron Transfer ◽

Spectroscopy Observation

Download Full-text

Electron self-exchange activation parameters of diethyl sulfide and tetrahydrothiophene

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.9.164 ◽

2013 ◽

Vol 9 ◽

pp. 1448-1454

Author(s):

Martin Goez ◽

Martin Vogtherr

Keyword(s):

Electron Transfer ◽

Photoinduced Electron Transfer ◽

Nuclear Polarization ◽

Activation Barrier ◽

Activation Parameters ◽

Radical Cations ◽

Free Energies ◽

Time Resolved ◽

Diethyl Sulfide ◽

Chemically Induced

Electron transfer between the title compounds and their radical cations, which were generated by photoinduced electron transfer from the sulfides to excited 2,4,6-triphenylpyrylium cations, was investigated by time-resolved measurements of chemically induced dynamic nuclear polarization (CIDNP) in acetonitrile. The strongly negative activation entropies provide evidence for an associative–dissociative electron exchange involving dimeric radical cations. Despite this mechanistic complication, the free energies of activation were found to be well reproduced by the Marcus theory of electron transfer, with the activation barrier still dominated by solvent reorganization.

Download Full-text