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
1995 ◽  
Vol 102 (17) ◽  
pp. 6787-6805 ◽  
Author(s):  
Kueih‐Tzu Lu ◽  
Frank Weinhold ◽  
James C. Weisshaar

1987 ◽  
Vol 7 (2-4) ◽  
pp. 197-212 ◽  
Author(s):  
Katsuhiko Okuyama ◽  
Naohiko Mikami ◽  
Mitsuo Ito

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.


Author(s):  
Kueih-Tzu Lu ◽  
Erik C. Richard ◽  
Robert A. Walker ◽  
James C. Weisshaar

Author(s):  
Erik C. Richard ◽  
Kueih-Tzu Lu ◽  
Robert A. Walker ◽  
James C. Weisshaar

1967 ◽  
Vol 22 (11) ◽  
pp. 1738-1743 ◽  
Author(s):  
H. D. Rudolph ◽  
H. Dreizler ◽  
H. Seiler

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.


2000 ◽  
Vol 179 ◽  
pp. 379-380
Author(s):  
Gaetano Belvedere ◽  
Kirill Kuzanyan ◽  
Dmitry Sokoloff

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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