Steric effects in [2.2]metaparacyclophanes. Steric isotope effect, remote substituent effect on a steric barrier, and other steric phenomena

1974 ◽  
Vol 96 (5) ◽  
pp. 1565-1577 ◽  
Author(s):  
S. A. Sherrod ◽  
R. L. Da Costa ◽  
R. A. Barnes ◽  
V. Boekelheide
Keyword(s):  
Isotope Effect ◽  
Substituent Effect ◽  
Steric Effects ◽  
Remote Substituent

scholarly journals Photochemical Transformation of some 3-benzyloxy-2-(benzo[b]thiophen-2-yl)-4Hchromen-4-ones: A Remote Substituent Effect

2018 ◽  
Vol 16 (1) ◽  
pp. 79-86
Author(s):  
Aarti Dalal ◽  
Radhika Khanna ◽  
Ramesh C. Kamboj
Keyword(s):  
Substituent Effect ◽  
Product Yield ◽  
Photochemical Transformation ◽  
Spectroscopic Techniques ◽  
Reaction Site ◽  
State Switching ◽  
Photochemical Transformations ◽  
Remote Substituent ◽  
Electron Donating Groups

AbstractThe effect on photochemical transformations of the substituents present remotely from the reaction site in 3-benzyloxy-2-(benzo[b]thiophen-2-yl)-4H-chromen-4-ones has been determined. The structure(s) of the substrates and photoproducts were established by spectroscopic techniques (UV, IR, and NMR). The substituents had profound effects on product yield and distribution. Electron withdrawing groups (EWGs) on the benzenoid moiety of the chromenone nucleus increased the yield of the photoproducts whereas electron donating groups (EDGs) decreased the yield. These results may be attributed to “state switching” of the substituents during excitation.

Sterically Hindered Aromatic Compounds. VI. A Remote ε-Deuterium Kinetic Isotope Effect in the Solvolysis of Perdeutero-2,4,6-tri-tert-butylbenzyl Chloride

1975 ◽  
Vol 53 (21) ◽  
pp. 3171-3174 ◽  
Author(s):  
L. Ross C. Barclay ◽  
John R. Mercer ◽  
Peter J. MacAulay
Keyword(s):  
Transition State ◽  
Isotope Effect ◽  
Aromatic Compounds ◽  
Kinetic Isotope Effect ◽  
Inductive Effect ◽  
Steric Effects ◽  
Deuterium Isotope Effect ◽  
Tert Butyl ◽  
Kinetic Isotope ◽  
Sterically Hindered

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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