Effect of Temperature, Solvent Polarity, and Nature of Lewis Acid on the Rate Constants in the Carbocationic Polymerization of Isobutylene

2003 ◽  
Vol 36 (22) ◽  
pp. 8282-8290 ◽  
Author(s):  
Laszlo Sipos ◽  
Priyadarsi De ◽  
Rudolf Faust
Keyword(s):  
Lewis Acid ◽  
Rate Constants ◽  
Solvent Polarity ◽  
Effect Of Temperature ◽  
Carbocationic Polymerization

Determination of Rate Constants in the Carbocationic Polymerization of Styrene:  Effect of Temperature, Solvent Polarity, and Lewis Acid1

2004 ◽  
Vol 37 (12) ◽  
pp. 4422-4433 ◽  
Author(s):  
Priyadarsi De ◽  
Rudolf Faust ◽  
Holger Schimmel ◽  
Armin R. Ofial ◽  
Herbert Mayr
Keyword(s):  
Rate Constants ◽  
Solvent Polarity ◽  
Effect Of Temperature ◽  
Carbocationic Polymerization

Efficient photoinduced electron transfer between C60/C70 and zinc octaethylporphyrin studied by nanosecond laser photolysis method

2000 ◽  
Vol 04 (06) ◽  
pp. 591-598 ◽  
Author(s):  
MOHAMED E. EL-KHOULY ◽  
MAMORU FUJITSUKA ◽  
OSAMU ITO
Keyword(s):  
Electron Transfer ◽  
Rate Constants ◽  
Photoinduced Electron Transfer ◽  
Transfer Rate ◽  
Transient Absorption ◽  
Laser Light ◽  
Solvent Polarity ◽  
Nanosecond Laser ◽  
Electron Transfer Rate ◽  
Absorption Bands

Photoinduced electron-transfer processes between C 60 or C 70 and zinc octaethylporphyrin ( ZnOEP ) have been studied in polar solvents with the nanosecond laser flash photolysis method, observing the transient absorption spectra in the visible and near-IR regions. By the predominant excitation of ZnOEP with 532 nm laser light the transient absorption bands of 3 ZnOEP * decayed, accompanied by the appearance of the transient absorption bands of [Formula: see text] and [Formula: see text]. By the predominant excitation of C 60 and C 70 with 610 nm laser light the decays of [Formula: see text] and [Formula: see text] were observed, accompanied by the appearance of [Formula: see text] and [Formula: see text]. The electron transfer rate constants (k et ) and the quantum yields (Φ et ) of [Formula: see text] and [Formula: see text] formation via 3 ZnOEP * and [Formula: see text] or [Formula: see text] have been evaluated. These values increase with the solvent polarity; in polar benzonitrile these values are higher than for other porphyrins such as zinc tetraphenylporphyrin. The back electron transfer rate constants were evaluated from the decays of [Formula: see text] and [Formula: see text], which also show a solvent polarity dependence.

ChemInform Abstract: Control of Hetero-Diels-Alder Stereoselectivity Through Solvent Polarity and Broensted or Lewis Acid Catalysis; Theory and Experiment.

ChemInform ◽  
2014 ◽  
Vol 45 (12) ◽  
pp. no-no
Author(s):  
Olivier Loiseleur ◽  
Jerome Cassayre ◽  
Dominique Leca ◽  
Francesca Gaggini ◽  
Susan N. Pieniazek ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Acid Catalysis ◽  
Solvent Polarity ◽  
Diels Alder ◽  
Lewis Acid Catalysis ◽  
Theory And Experiment

Die Lösungsmittelabhängigkeit der thermischen cis-trans-Isomerisierung von N-Benzylidenanilinen mit Donator/Akzeptor-Substituenten.

1976 ◽  
Vol 31 (7) ◽  
pp. 953-959 ◽  
Author(s):  
U. Berns ◽  
G. Heinrich ◽  
H. Gusten
Keyword(s):  
Ground State ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Solvent Polarity ◽  
Linear Functions ◽  
Aryl Group ◽  
Trans Isomerization ◽  
Solvatochromic Shifts ◽  
Z Value ◽  
Inversion Mechanism

Thermal cis →-trans isomerization of eight N-benzylideneanilines with donor and/or acceptor substituents in the para, para'-positions was studied in different solvents by observing the rapid relaxation to the thermodynamic stable trans isomer following flash photolysis. With the push-pull effect of the substituents in the direction of the N-aryl group the rate constant at 25°C is by three powers of 10 faster compared to the N–benzylideneaniline with opposite arrangement of substituents. The rate constants are independent of the nature of the substituents in the para-position of the benzylidene group. The rate constants of N-(4-nitrobenzylidene)-p-anisidine are linear functions of the solvent polarity scale based on solvatochromic shifts (Kosowers Z-value or Dimroths ET-value). With increasing push-pull effect of the substituents in the direction of the N-aryl group the rate constants do no longer depend on the polarity of the solvent. The observed solvent effects on the rates and the activation energies for thermal cis→ trans isomerization suggest that the transition state of the reaction is less polar than the ground state of the sterically hindered cis-N-benzylideneaniline, thus favouring an inversion mechanism to become operative with respect to the N-benzylideneanilines.

The effect of temperature on the optical spectra and the yields of solvated electrons and ion-pairs in amines

1978 ◽  
Vol 56 (6) ◽  
pp. 839-843 ◽  
Author(s):  
William Arthur Seddon ◽  
John Wallace Fletcher ◽  
Fred Charles Sopchyshyn
Keyword(s):  
Ion Pairs ◽  
Solvent Polarity ◽  
Solute Concentration ◽  
Ion Pair ◽  
Effect Of Temperature ◽  
Gradual Transition ◽  
Solvated Electron ◽  
Solvated Electrons ◽  
Extinction Coefficients ◽  
Yield Formula

Optical absorption spectra for the solvated electron, es−, and ion-pairs, (Na+, es−), have been observed in methylamine (MA), ethylamine (EA), and isopropylamine (IPA), at temperatures ranging from 184 to 338 K. Changes in the (Na+, es−) spectra, relative to es−, are consistent with a gradual transition in the ion-pair structure toward a more 'electron-like' entity with decreasing temperature and increasing solvent polarity. Extinction coefficients, εmax(es−) = 3.3 ± 0.2, 3.2 ± 0.5, and 3.2 ± 0.5 × 104 M−1 cm−1 in MA, EA, and IPA respectively. Corresponding values for the ion-pairs, εmax(Na+, es−) = 2.5 ± 0.2, 2.1 ± 0.2, and 1.9 ± 0.2 × 104 M−1 cm−1.In EA and IPA, the yield [Formula: see text] (molecules/100 eV) shows a marked solute concentration dependence. This is consistent with an empirical scavenging model from which the escaped solvated G(es−)esc and spur G(es−)spur electrons are estimated as G(es−)esc = 0.5 and 0.4, G(es−)spur = 1.8 and 1.4, giving G(es−)total = 2.3 and 1.8 in EA and IPA, respectively. In MA, [Formula: see text] = G(es−)esc = 2.25 ± 0.2, independent of solute concentration.

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