Kinetic Isotope Effect Probes the Reactive Spin State, As Well As the Geometric Feature and Constitution of the Transition State during H-Abstraction by Heme Compound II Complexes

2017 ◽  
Vol 139 (33) ◽  
pp. 11451-11459 ◽  
Author(s):  
Dibyendu Mallick ◽  
Sason Shaik

2009 ◽  
Vol 15 (34) ◽  
pp. 8492-8503 ◽  
Author(s):  
Chunsen Li ◽  
Wei Wu ◽  
Kyung-Bin Cho ◽  
Sason Shaik




2004 ◽  
Vol 82 (9) ◽  
pp. 1336-1340
Author(s):  
Xicai Huang ◽  
Andrew J Bennet

The aqueous ethanolysis reactions of adamantylideneadamantyl tosylate, -bromide, and -iodide (1-OTs, 1-Br and 1-I) were monitored as a function of ionic strength. Special salt effects are observed during the solvolyses of both homoallylic halides, but not in the case of the tosylate 1-OTs. The measured α-secondary deuterium kinetic isotope effects for the solvolysis of 1-Br in 80:20 and 60:40 v/v ethanol–water mixtures at 25 °C are 1.110 ± 0.018 and 1.146 ± 0.009, respectively. The above results are consistent with the homoallylic halides reacting via a virtual transition state in which both formation and dissociation of a solvent-separated ion pair are partially rate-determining. While the corresponding transition state for adamantylideneadamantyl tosylate involves formation of the solvent-separated ion pair.Key words: salt effects, kinetic isotope effect, internal return, solvolysis, ion pairs.



1975 ◽  
Vol 53 (21) ◽  
pp. 3171-3174 ◽  
Author(s):  
L. Ross C. Barclay ◽  
John R. Mercer ◽  
Peter J. MacAulay

2,4,6-Tri-tert-butylbenzyl chloride deuterated at the three tert-butyl groups was synthesized. Conductimetric solvolysis studies of the normal and perdeutero-2,4,6-tri-tert-butylbenzyl chloride at 30.06 °C in 80% ethanol–water provides evidence for an inverse remote ε-deuterium isotope effect, kH/kD = 0.873−0.874. Under the same conditions the α-deuterium isotope effect was kH/kαD = 1.166 per deuterium, indicative of limiting solvolytic behavior. The remote ε-deuterium isotope effect for the perdeutero compound is discussed in terms of the inductive effect of deuterium and steric effects on the transition state conformation.



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