Switchable Conformational Isomerization of an Overcrowded Tristricyclic Aromatic Ene

2019 ◽  
Vol 85 (1) ◽  
pp. 179-186 ◽  
Author(s):  
Tomohiko Nishiuchi ◽  
Ryuoh Ito ◽  
Erik Stratmann ◽  
Takashi Kubo
Keyword(s):  
Conformational Isomerization

scholarly journals Conformational Isomerization of Formic Acid by Vibrational Excitation at Energies below the Torsional Barrier

2003 ◽  
Vol 125 (14) ◽  
pp. 4058-4059 ◽  
Author(s):  
Mika Pettersson ◽  
Ermelinda M. S. Maçôas ◽  
Leonid Khriachtchev ◽  
Rui Fausto ◽  
Markku Räsänen
Keyword(s):  
Formic Acid ◽  
Vibrational Excitation ◽  
Conformational Isomerization ◽  
Torsional Barrier

Dynamical solvent effects on conformational isomerization of cyclohexane and 1,1‐difluorocyclohexane

1989 ◽  
Vol 90 (10) ◽  
pp. 5386-5391 ◽  
Author(s):  
Joseph Ashcroft ◽  
Chuan‐Liang Xie ◽  
Jiri Jonas
Keyword(s):  
Solvent Effects ◽  
Conformational Isomerization

Benzene-1,2-disulfonate dianion: another compound with meshed cogwheel substituents?

1996 ◽  
Vol 52 (3) ◽  
pp. 562-568 ◽  
Author(s):  
N. Nagel ◽  
P. Eller ◽  
H. Bock
Keyword(s):  
Crystal Structures ◽  
Disulfonic Acid ◽  
Conformational Isomerization ◽  
Tetramethylammonium Salts

Crystal structures of the dipotassium and potassium tetramethylammonium salts of benzene-1,2-disulfonic acid have been determined at 200 K and a PM3 enthalpy hypersurface for the substituent rotations of the free benzene-1,2-disulfonate dianion was calculated. The cogging of the two sulfonate groups as well as the possible pathways of conformational isomerization are discussed and compared with already investigated molecules containing adjacent threefold substituents.

Direct measurement of the energy thresholds to conformational isomerization in Tryptamine: Experiment and theory

2005 ◽  
Vol 122 (21) ◽  
pp. 214311 ◽  
Author(s):  
Jasper R. Clarkson ◽  
Brian C. Dian ◽  
Loïck Moriggi ◽  
Albert DeFusco ◽  
Valerie McCarthy ◽  
...  
Keyword(s):  
Direct Measurement ◽  
Conformational Isomerization ◽  
Energy Thresholds

HINDERED CONFORMATIONAL ISOMERIZATION OF 9,10-DIHYDRO-9,9-DIMETHYL-10-METHYLENEANTHRACENES

1964 ◽  
Vol 42 (3) ◽  
pp. 565-571 ◽  
Author(s):  
D. Y. Curtin ◽  
C. G. Carlson ◽  
C. G. McCarty
Keyword(s):  
Room Temperature ◽  
Methyl Groups ◽  
Conformational Isomerization ◽  
Methylene Carbon ◽  
Methyl Group ◽  
First Order ◽  
Methylene Carbon Atom ◽  
Center Ring ◽  
Bromo Compound ◽  
Dibromo Derivative

While the n.m.r. spectrum of 10,10-dimethyl-9-methylene-9,10-dihydroanthracene (I) shows the geminal methyl group absorption as a sharp singlet the spectrum of the dibromo derivative, 10,10-dimethyl-9-dibromomethylene-9,10-dihydroanthracene (II) shows the methyl absorptions as two sharp well-separated peaks at room temperature which coalesce at 91°. 10,10-Dimethyl-9-phenylbromomethylene-9,10-dihydroanthracene (III), and the methyl ester (V) of IV show a broad geminal methyl spectrum at room temperature which separates to a doublet at lower temperatures and sharpens to a singlet at higher temperatures. Rate constants for the first-order processes responsible for the change in spectrum of II, III, and V have been calculated at the coalescence temperatures to be 57 (364 °K), 35 (305 °K), and 61 (300 °K) sec−1, respectively. The ΔH≠'s were used to extrapolate the rates to 305° to give values of 1, 40, and 100 sec−1, respectively. The process being studied is inferred to be the equilibrium between two boat conformations of the center ring in the dihydroanthracene system, rapid interconversion leading to identical environments for the two methyl groups. A comparison with the geometrically similar o,o′-disubstituted biphenyl racemization gives support for this explanation. A number of compounds with a proton and one substituent on the methylene carbon atom of I (substituents: bromine, chlorine, phenyl, carboxy, carbomethoxy, phenylmercapto) and also 10,10-dimethyl-9-phenylcarbomethoxymethylene-9,10-dihydroanthracene (XII) showed a single methyl absorption at room temperature. The methyl spectrum of the mono bromo compound VI did not broaden at temperatures down to 246 °K.

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