نتایج جستجو برای: Boat-chair conformation

تعداد نتایج: 58910  

Hassan Kabiri-Fard Issa Yavari

Ab initio calculations at HF/6-31G* level of theory for geometry optimization and MP2/6-31G*//HF/6-31G*for total energy calculation are reported for Z-cyclooctene (1). The most favorable conformation of 1 is theunsymmetric boat-chair (1-BC) geometry. Potential energy profiles for two different boat-chair/boat-chairinterconversion processes were calculated. The process via a chair transition sta...

Journal: :journal of physical & theoretical chemistry 2015
issa yavari hassan kabiri-fard

ab initio calculations at hf/6-31g* level of theory for geometry optimization and mp2/6-31g*//hf/6-31g*for total energy calculation are reported for z-cyclooctene (1). the most favorable conformation of 1 is theunsymmetric boat-chair (1-bc) geometry. potential energy profiles for two different boat-chair/boat-chairinterconversion processes were calculated. the process via a chair transition sta...

Journal: :iranian journal of chemistry and chemical engineering (ijcce) 1995
mehran ghiaci ahmad reza massah

the 1h and natural-abundance 13c-nmr spectra of 1-thiacyclooctan-3-one (1) have been measured from 25 to -100°c. coalescence is observed in the 1h-nmr spectra of (1) at about -80°c, and attributed to ring inversion in a boat-chair conformation, which is the predominant conformation of (1). the free energy of activation (dg¹) for this process is 9.2±0.2 kcal/mol. the 13c-nmr spectra of (1) is te...

ژورنال: مواد پرانرژی 2017

1,5-Diazabicyclo[3.1.0]hexane (DABH) is the unusual and highly energetic derivative of the diaziridine, because cis-diaziridines are thermodynamically less stable than the trans-isomers. therefore, the investigation of DABH molecule has practical importance besides fundamental research. Three possible conformations of DABH were considered: boat, chair, and twist. According to the published repo...

Journal: :Organic & biomolecular chemistry 2009
Jun Cheng Tsutomu Hoshino

The enzymatic cyclization reaction of polyprenoid C(33) by squalene-hopene cyclase (SHC) was investigated with the intention of creating an unnatural hexacyclic compound. The enzymatic products consisted of mono-, bi-, tri-, tetra- and pentacyclic skeletons; however, hexacyclic products were not generated, contrary to our expectations. The absence of a hexacyclic skeleton indicated that the ent...

Ahmad Reza Massah Mehran Ghiaci

The 1H and natural-abundance 13C-NMR spectra of 1-thiacyclooctan-3-one (1) have been measured from 25 to -100°C. Coalescence is observed in the 1H-NMR spectra of (1) at about -80°C, and attributed to ring inversion in a boat-chair conformation, which is the predominant conformation of (1). The free energy of activation (DG¹</s...

Issa Yavari Mohsen Dadgar Vahideh Hadigheh-Rezvan

Ab initio calculations at HF/6-31G* level of theory for geometry optimization and MP2/6-31G*//HF/6-31G* for a single point total energy calculation are reported for the importantenergy-minimum conformations and transition-state geometries of 1, 3-diazacyclohepta-1, 2-diene (2) and 1, 3-diazacycloocta-1, 2-diene (3). The C2 symmetric twist-chair (2-TC)conformation of 2 is calculated to be 7.4 kJ...

Journal: :journal of physical & theoretical chemistry 2004
issa yavari vahideh hadigheh-rezvan mohsen dadgar

ab initio calculations at hf/6-31g* level of theory for geometry optimization and mp2/6-31g*//hf/6-31g* for a single point total energy calculation are reported for the importantenergy-minimum conformations and transition-state geometries of 1, 3-diazacyclohepta-1, 2-diene (2) and 1, 3-diazacycloocta-1, 2-diene (3). the c2 symmetric twist-chair (2-tc)conformation of 2 is calculated to be 7.4 kj...

Journal: :The Journal of organic chemistry 2007
Diwakar M Pawar Dalephine Cain Gurvinder Gill Alex D Bain Richard H Sullivan Eric A Noe

Interconversion of carbon sites in boat-chair-boat (BCB) cyclodecane occurs by way of the twist-boat-chair (TBC) conformation, which predicts that C-1 exchanges with C-4, etc. The previously obtained low-temperature 13C spectra could be matched by assuming (1,4) or (1,3) exchange, but not (1,2) exchange. A free-energy barrier of 5.54 kcal/mol was obtained for conversion of BCB to TBC at -137.4 ...

Journal: :Forests 2022

Triterpenes are natural products of plants that can defend against microorganisms and various stresses. Oxidosqualene cyclase (OSC), the key rate-limiting enzyme triterpene biosynthetic pathway, catalyzes 2,3-oxidosqualene into sterols triterpenes with different skeletons through chair–boat–chair (CBC) conformation or chair–chair–chair (CCC) conformation. They were expanded in mainly by tandem ...

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