Enthalpies of solvent transfer of the transition states in the cis-trans isomerization of azo compounds. Rotation vs. the nitrogen inversion mechanism

1975 ◽  
Vol 97 (20) ◽  
pp. 5804-5806 ◽  
Author(s):  
Paul Haberfield ◽  
Paul M. Block ◽  
Michael S. Lux
Keyword(s):  
Transition States ◽  
Azo Compounds ◽  
Nitrogen Inversion ◽  
Trans Isomerization ◽  
Inversion Mechanism ◽  
Solvent Transfer

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.

New theoretical insight into the thermal cis–trans isomerization of azo compounds: Protonation lowers the activation barrier

2001 ◽  
Vol 114 (13) ◽  
pp. 5504-5508 ◽  
Author(s):  
W. A. Sokalski ◽  
R. W. Góra ◽  
W. Bartkowiak ◽  
P. Kobyliński ◽  
J. Sworakowski ◽  
...  
Keyword(s):  
Activation Barrier ◽  
Azo Compounds ◽  
Trans Isomerization ◽  
Theoretical Insight ◽  
Insight Into

Theoretical study on thermal cis -to- trans isomerization of BF 2 -coordinated azo compounds of the para-substitution with electron donating groups

2016 ◽  
Vol 129 ◽  
pp. 100-108 ◽  
Author(s):  
Yong-Peng Wang ◽  
Zhi-Xiang Zhang ◽  
Miao Xie ◽  
Fu-Quan Bai ◽  
Pi-Xia Wang ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Azo Compounds ◽  
Trans Isomerization ◽  
Electron Donating Groups

Temperature and pressure dependences of thermal cis-to-trans isomerization of azobenzenes which evidence an inversion mechanism

1981 ◽  
Vol 103 (17) ◽  
pp. 5161-5165 ◽  
Author(s):  
Tsutomu Asano ◽  
Toshio Okada ◽  
Seiji Shinkai ◽  
Kazuyoshi Shigematsu ◽  
Yumiko Kusano ◽  
...  
Keyword(s):  
Trans Isomerization ◽  
Temperature And Pressure ◽  
Inversion Mechanism
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