Low-Temperature 13C Magnetic Resonance. 9.Steric Effects for Methyl Chemical Shift Tensors in Methylcyclohexanes

Soderquist, Arlen; Facelli, Julio C.; Horton, W. J.; Grant, David M.

doi:10.1021/ja00137a020

Cited by 19 publications

(19 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…19͒ and 1.8 kcal/mol at 173 K. 20 The steric interactions in methylcyclohexane have been the subject of a large number of publications. [21][22][23][24][25] It was shown that the repulsive ͑gauche-butane, g.b) interactions dominate the overall energetics. It is clear that there are 2 g.b repulsive interactions in the axial conformation of MCH, and no g.b interactions in the equatorial conformation.…”

Section: Discussionmentioning

confidence: 99%

Premelting structure: Vibrational dynamics of liquid, undercooled liquid, glassy, and crystal states in methylcyclohexane and deuterated methylcyclohexane

Abramczyk

Paradowska-Moszkowska

Wiosna

2003

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

Section: Discussionmentioning

confidence: 99%

Premelting structure: Vibrational dynamics of liquid, undercooled liquid, glassy, and crystal states in methylcyclohexane and deuterated methylcyclohexane

Abramczyk

Paradowska-Moszkowska

Wiosna

2003

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…In order to compare the effect of substitution at position 4 with the unsubstituted case, we included ketone 1g (R = H) in the study as a reference point. [41] Access to the model substrates proceeded in a straightforward manner. The mono-protected quinone 4 is a readily available precursor for the subsequent functionalization.…”

Section: Scheme 2 Lactone 3a As a Key Intermediate For The Synthesismentioning

confidence: 99%

Microbial Baeyer–Villiger Oxidation of Prochiral Polysubstituted Cyclohexanones by Recombinant Whole‐Cells Expressing Two Bacterial Monooxygenases

Mihovilovic¹,

Rudroff²,

Grötzl³

et al. 2005

Eur J Org Chem

View full text Add to dashboard Cite

The microbial Baeyer-Villiger oxidation of prochiral 3,5-dimethylcyclohexanones bearing various functionalities with recombinant E. coli cells overexpressing cyclohexanone monooxygenase from Acinetobacter sp. NCIMB 9871 and cyclopentanone monooxygenase from Comamonas sp. NCIMB 9872 has been investigated. A distinct difference in substrate specificity and stereoselectivity of the two enzymes was observed, and enantiocomplementary products were obtained in some cases. The biocatalytic systems enabled ac-

show abstract

“…This is consistent with the presence of at least five structurally unique defect sites. A tentative assignment of each site can be made using prior work establishing that methyl groups at lower frequencies represent those most sterically imposed upon by neighboring sites. − A summary of C–H···X steric interactions (X = N or B) for each structural model is given in Table . Site 1, represented by the signal near 7 ppm, is only occupied at low surface coverages and, on the basis of the 13 C shift, is expected to display the most significant steric interactions with neighboring atoms.…”

Section: Resultsmentioning

confidence: 99%

Heterogeneous Metal-Free Hydrogenation over Defect-Laden Hexagonal Boron Nitride

Nash

Restrepo

Parra³

et al. 2016

ACS Omega

View full text Add to dashboard Cite

Catalytic hydrogenation is an important process used for the production of everything from foods to fuels. Current heterogeneous implementations of this process utilize metals as the active species. Until recently, catalytic heterogeneous hydrogenation over a metal-free solid was unknown; implementation of such a system would eliminate the health, environmental, and economic concerns associated with metal-based catalysts. Here, we report good hydrogenation rates and yields for a metal-free heterogeneous hydrogenation catalyst as well as its unique hydrogenation mechanism. Catalytic hydrogenation of olefins was achieved over defect-laden h- BN ( dh -BN) in a reactor designed to maximize the defects in h- BN sheets. Good yields (>90%) and turnover frequencies (6 × 10 –5 –4 × 10 –3 ) were obtained for the hydrogenation of propene, cyclohexene, 1,1-diphenylethene, ( E )- and ( Z )-1,2-diphenylethene, octadecene, and benzylideneacetophenone. Temperature-programmed desorption of ethene over processed h -BN indicates the formation of a highly defective structure. Solid-state NMR (SSNMR) measurements of dh -BN with high and low propene surface coverages show four different binding modes. The introduction of defects into h- BN creates regions of electronic deficiency and excess. Density functional theory calculations show that both the alkene and hydrogen-bond order are reduced over four specific defects: boron substitution for nitrogen (B N ), vacancies (V B and V N ), and Stone–Wales defects. SSNMR and binding-energy calculations show that V N are most likely the catalytically active sites. This work shows that catalytic sites can be introduced into a material previously thought to be catalytically inactive through the production of defects.

show abstract

Low-Temperature 13C Magnetic Resonance. 9.Steric Effects for Methyl Chemical Shift Tensors in Methylcyclohexanes

Cited by 19 publications

References 0 publications

Premelting structure: Vibrational dynamics of liquid, undercooled liquid, glassy, and crystal states in methylcyclohexane and deuterated methylcyclohexane

Premelting structure: Vibrational dynamics of liquid, undercooled liquid, glassy, and crystal states in methylcyclohexane and deuterated methylcyclohexane

Microbial Baeyer–Villiger Oxidation of Prochiral Polysubstituted Cyclohexanones by Recombinant Whole‐Cells Expressing Two Bacterial Monooxygenases

Heterogeneous Metal-Free Hydrogenation over Defect-Laden Hexagonal Boron Nitride

Contact Info

Product

Resources

About