ChemInform Abstract: Methyl Internal Rotation in Substituted Toluenes: Effects of Substituents, Electronic Excitation, and Ionization

ChemInform ◽  
2010 ◽  
Vol 31 (28) ◽  
pp. no-no
Author(s):  
Kueih-Tzu Lu ◽  
Erik C. Richard ◽  
Robert A. Walker ◽  
James C. Weisshaar
Keyword(s):  
Internal Rotation ◽  
Electronic Excitation ◽  
Substituted Toluenes

Understanding barriers to internal rotation in substituted toluenes and their cations

1995 ◽  
Vol 102 (17) ◽  
pp. 6787-6805 ◽  
Author(s):  
Kueih‐Tzu Lu ◽  
Frank Weinhold ◽  
James C. Weisshaar
Keyword(s):  
Internal Rotation ◽  
Substituted Toluenes ◽  
Barriers To Internal Rotation

scholarly journals Internal Rotation of the Methyl Group in the Electronically Excited State: o- and m-Toluidine

1987 ◽  
Vol 7 (2-4) ◽  
pp. 197-212 ◽  
Author(s):  
Katsuhiko Okuyama ◽  
Naohiko Mikami ◽  
Mitsuo Ito
Keyword(s):  
Excited State ◽  
Internal Rotation ◽  
Barrier Height ◽  
Ground State ◽  
Electronic Excitation ◽  
Vibrational Analysis ◽  
Fluorescence Excitation ◽  
Close Relationship ◽  
Electronically Excited ◽  
Dispersed Fluorescence

The fluorescence excitation and dispersed fluorescence spectra of jet-cooled o- and m-toluidine were observed. Vibrational analysis of the spectra provided us with the potentials for the internal rotation of the CH3 group in both ground and excited states. In o-toluidine, a large potential barrier to the internal rotation in the ground state is practically removed in the excited state. On the other hand, a nearly free internal rotation of the CH3 group in the ground state of m-toluidine gains a large barrier by the electronic excitation. The great change in the barrier height upon the electronic excitation is more remarkable than that found for fluorotoluene. A close relationship between the barrier height and the π electron density at the ring carbon atom was found, indicating the hyperconjugation as the origin of the barrier height in the absence of steric hindrance.

Methyl Internal Rotation in Substituted Toluenes

1999 ◽  
pp. 307-334
Author(s):  
Kueih-Tzu Lu ◽  
Erik C. Richard ◽  
Robert A. Walker ◽  
James C. Weisshaar
Keyword(s):  
Internal Rotation ◽  
Substituted Toluenes

Barriers to internal rotation in substituted toluenes and their cations

1998 ◽  
pp. 157-183 ◽  
Author(s):  
Erik C. Richard ◽  
Kueih-Tzu Lu ◽  
Robert A. Walker ◽  
James C. Weisshaar
Keyword(s):  
Internal Rotation ◽  
Substituted Toluenes ◽  
Barriers To Internal Rotation

Hinderungspotential der internen Rotation, Dipolmoment und Quadrupolkopplungskonstanten aus dem Mikrowellenspektrum des 4-Methyl-Pyridins

1967 ◽  
Vol 22 (11) ◽  
pp. 1738-1743 ◽  
Author(s):  
H. D. Rudolph ◽  
H. Dreizler ◽  
H. Seiler
Keyword(s):  
Dipole Moment ◽  
Internal Rotation ◽  
Potential Barrier ◽  
Coupling Constants ◽  
Rotational Spectrum ◽  
A Value ◽  
Microwave Rotational Spectrum ◽  
Quadrupole Coupling ◽  
Substituted Toluenes ◽  
Nuclear Quadrupole

The microwave rotational spectrum of 4-methyl-pyridine (γ-picoline) has been investigated in the region from 8 to 37 GHz. The three types of lines to be expected for a molecule of this symmetry and with a very low sixfold barrier hindering internal rotation of the methyl top have been found: m=0; | m | ≠0, ≠ 3 n; | m |=3 n. From low-/ lines m=0 (a-type transitions) the rotational constants A′ (less methyl top) =6 082.145, B=2 524.850, C=1 783.991 MHz, the dipole moment μα=2.70 D, and the nuclear quadrupole coupling constants for the 14N nucleus χaa= —4.82, χbb—χcc= —2.8 MHz have been determined. From the wide splitting of the lines | m | = 3, | K | = 1 the potential barrier has been derived as V6=13.51 cal/mole, a value which is very close to those previously deduced for toluene and para-substituted toluenes.

Solar Internal Rotation and Dynamo Waves: A Two-Dimensional Asymptotic Solution in the Convection Zone

2000 ◽  
Vol 179 ◽  
pp. 379-380
Author(s):  
Gaetano Belvedere ◽  
Kirill Kuzanyan ◽  
Dmitry Sokoloff
Keyword(s):  
Magnetic Field ◽  
Asymptotic Solution ◽  
Internal Rotation ◽  
Convection Zone ◽  
General Idea ◽  
Dynamo Model ◽  
Axially Symmetric ◽  
Dynamo Action ◽  
Regeneration Rate ◽  
Dynamo Waves

Extended abstractHere we outline how asymptotic models may contribute to the investigation of mean field dynamos applied to the solar convective zone. We calculate here a spatial 2-D structure of the mean magnetic field, adopting real profiles of the solar internal rotation (the Ω-effect) and an extended prescription of the turbulent α-effect. In our model assumptions we do not prescribe any meridional flow that might seriously affect the resulting generated magnetic fields. We do not assume apriori any region or layer as a preferred site for the dynamo action (such as the overshoot zone), but the location of the α- and Ω-effects results in the propagation of dynamo waves deep in the convection zone. We consider an axially symmetric magnetic field dynamo model in a differentially rotating spherical shell. The main assumption, when using asymptotic WKB methods, is that the absolute value of the dynamo number (regeneration rate) |D| is large, i.e., the spatial scale of the solution is small. Following the general idea of an asymptotic solution for dynamo waves (e.g., Kuzanyan & Sokoloff 1995), we search for a solution in the form of a power series with respect to the small parameter |D|–1/3(short wavelength scale). This solution is of the order of magnitude of exp(i|D|1/3S), where S is a scalar function of position.

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