Stereoelectronic effects in a homologous series of bidentate cyclic phosphines. A clear correlation of hydroformylation catalyst activity with ring size

2009 ◽  
pp. 202-209 ◽  
Author(s):  
Mairi F. Haddow ◽  
Ann J. Middleton ◽  
A. Guy Orpen ◽  
Paul G. Pringle ◽  
Rainer Papp
Keyword(s):  
Homologous Series ◽  
Catalyst Activity ◽  
Clear Correlation ◽  
Ring Size ◽  
Stereoelectronic Effects

Bis(monoazacrown ether)s: Effects of bridge length and ring size on stability and selectivity in alkali ion sandwich complex formation

1991 ◽  
Vol 56 (7) ◽  
pp. 1482-1488 ◽  
Author(s):  
Petr Holý ◽  
Juraj Koudelka ◽  
Martin Bělohradský ◽  
Ivan Stibor ◽  
Jiří Závada
Keyword(s):  
Complex Formation ◽  
Homologous Series ◽  
Ring Size ◽  
Azacrown Ether ◽  
Sandwich Complex ◽  
Sodium Potassium ◽  
Alkali Ions ◽  
Potassium Complex ◽  
Bridge Length ◽  
Alkali Ion

Sodium, potassium, rubidium and caesium ion complex formation was investigated in two homologous series of bis(azacrown ether)s Ia-Ic and IIa-IIc. Three complementary bis(azacrown ether)s series IIIa-IIIc, IVa-IVc and Va-Vc were employed for a more detailed study of sodium complexation. Very pronounced effects of bridge length as well as macroring size were found in the investigated series and interpreted mainly in terms of various proclivity of individual ligands and alkali ions to sandwich complex formation. Remarkably high selectivities in alkali ion formation were noted for the shortest bridge ligands Ia and Ib, the former preferring strongly sodium and the latter potassium complex formation.

scholarly journals PtII-Catalyzed Ethylene Hydrophenylation: Influence of Dipyridyl Chelate Ring Size on Catalyst Activity and Longevity

ACS Catalysis ◽  
2013 ◽  
Vol 3 (6) ◽  
pp. 1165-1171 ◽  
Author(s):  
Bradley A. McKeown ◽  
Hector Emanuel Gonzalez ◽  
T. Brent Gunnoe ◽  
Thomas R. Cundari ◽  
Michal Sabat
Keyword(s):  
Chelate Ring ◽  
Catalyst Activity ◽  
Ring Size ◽  
Chelate Ring Size

1,2-Bis(azacrown)ethanes: Effect of Bridge Substitution and Ring Size on Formation of Sandwich Complexes with Sodium and Potassium Ions

1993 ◽  
Vol 58 (1) ◽  
pp. 153-158 ◽  
Author(s):  
Martin Bělohradský ◽  
Petr Holý ◽  
Juraj Koudelka ◽  
Jiří Závada
Keyword(s):  
Complex Formation ◽  
Homologous Series ◽  
Potassium Ions ◽  
Ring Size ◽  
Sandwich Complexes ◽  
Sandwich Complex ◽  
Symmetry Violation ◽  
Title Problem ◽  
Sodium And Potassium

The title problem was investigated potentiometrically using four homologous series of bis(azacrown)s I-IV. A surprisingly large destabilizing effect of bridge substituent was found in the intramolecular sandwich complex formation and ascribed to symmetry violation.

scholarly journals Challenges in Studying Steric Interactions in Highly Strained Perhalogenated Alkanes and Silanes.

2021 ◽  
Author(s):  
Luís Simões ◽  
RODRIGO CORMANICH
Keyword(s):  
Quantum Theory ◽  
Total Energy ◽  
Homologous Series ◽  
Nbo Analysis ◽  
Steric Effects ◽  
Electrostatic Effects ◽  
Steric Interactions ◽  
Stereoelectronic Effects ◽  
Helical Geometry ◽  
Highly Strained

The decomposition of the molecular total energy in their hyperconjugative, steric and electrostatic effects can lead to interesting interpretations about the stereoelectronic effects that govern their geometry and properties. In this work, we have studied homologous series of perfluoroalkanes, perchloroalkanes, perfluorosilanes and perchlorosilanes, and all molecules have preference for helical geometries. According to Natural Bond Orbitals (NBO) calculations, the silanes have their helical geometry stabilised by hyperconjugative interactions, as well as the perfluoroalkanes. However, it was surprisingly difficult to disclose that steric interactions are ruling the helical geometry preference in perchloroalkanes by comparing the NBO analysis and the Quantum Theory of Atoms ins Molecules (QTAIM). Although perchloroalkanes have extremely intense steric interactions between Cl lone pairs, some of them were underestimated by the NBO analysis, which showed the opposite behaviour compared with QTAIM that indicates steric effects as the leading forces to helical geometry preference.

NOVEL SMECTIC POLYMORPHIC BEHAVIOUR IN HOMOLOGOUS SERIES OF MESOGENS

1975 ◽  
Vol 36 (C1) ◽  
pp. C1-365-C1-374 ◽  
Author(s):  
D. COATES ◽  
G. W. GRAY
Keyword(s):  
Homologous Series

Does kraft hardwood and softwood pulp viscosity correlate to paper properties?

TAPPI Journal ◽  
2016 ◽  
Vol 15 (10) ◽  
pp. 643-651 ◽  
Author(s):  
ROBERT J. OGLESBY ◽  
HUMPHREY J. MOYNIHAN ◽  
RICARDO B. SANTOS ◽  
ASHOK GHOSH ◽  
PETER W. HART
Keyword(s):  
Physical Properties ◽  
Strength Loss ◽  
Strength Properties ◽  
Clear Correlation ◽  
Paper Properties ◽  
Physical Strength ◽  
Pulp Viscosity ◽  
Softwood Pulp ◽  
The Impact ◽  
Related Paper

The impact of commercially prepared, fully bleached pulp viscosity variation on handsheet physical properties was evaluated at different levels of pulp refining. Hardwood pulps from the same brownstock species mix, cooking parameters, and kappa numbers were processed through two different commercial bleach plants: one with a D0(EP)D1D2 sequence and the second with an OD0(EOP)D1 sequence. Additionally, a commercial softwood (predominately Scotts pine) brownstock pulp bleached by an OD0(EP)D1D2 sequence was employed in this study. Pulps with viscosities ranging from 14 to 21 mPa∙s were refined in a Valley beater to two freeness levels, and the associated handsheet physical properties were measured in this study. Over the pulp viscosity range of 14 to 21 mPa∙s, no clear correlation was found to exist between pulp viscosity and related paper physical properties. Finally, a series of laboratory prepared bleached pulps were purposely prepared under non-ideal conditions to reduce their final viscosities to lower values. Handsheets made from these pulps were tested in their unbeaten condition for physical strength properties. Significant and rapid strength loss occurred when the measured pulp viscosity dropped below 12 mPa∙s; overall strength properties showed no correlation to viscosity above the critical 12 mPa∙s value.

Ring size effect in McMurry cyclization of 1,ω-di((azulen-1-yl)-carbonyl) alkanes

2020 ◽  
Vol 65 (1) ◽  
pp. 83-88
Author(s):  
Eugenia Andreea DRAGU ◽  
◽  
Alexandru C. RAZUS ◽  
Keyword(s):  
Size Effect ◽  
Ring Size

LH-RH TEST IN 100 PATIENTS WITH OVARIAN INSUFFICIENCY

1974 ◽  
Vol 75 (3) ◽  
pp. 428-434 ◽  
Author(s):  
P.-J. Czygan ◽  
M. Breckwoldt ◽  
F. Lehmann ◽  
R. Langefeld ◽  
G. Bettendorf
Keyword(s):  
Intravenous Injection ◽  
Functional State ◽  
Clear Correlation ◽  
Normal Range ◽  
Ovarian Insufficiency ◽  
Lh Rh ◽  
Dose Dependent Increase ◽  
Dose Dependent

ABSTRACT The effect of synthetic LH-RH was studied in 100 patients with various types of ovarian insufficiency by following up the FSH- and LH-levels in plasma. LH-RH was administered in doses of 12.5, 25 and 100 μg as a rapid intravenous injection. The patients were classified according to the endocrine state of the pituitary as evidenced by the urinary gonadotrophin levels. A clear correlation between the functional state of the pituitary and its responsiveness to exogenous LH-RH was demonstrated. Most of the patients with undetectable low urinary gonadotrophin levels failed to respond. The majority of patients with gonadotrophin excretion in the normal range and those with elevated levels reacted with a dose dependent increase in circulating LH. The amount of liberated FSH however was related to the injected dose only in patients with high gonadotrophic excretion. The present study indicates that synthetic LH-RH provides a useful tool in the evaluation of the pitutiary function particularly in patients with low and with undetectable gonadotrophin excretion. The data presented in this paper also demonstrate that the functional state of the pituitary is clearly reflected by the urinary gonadotrophin levels.

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