scholarly journals Effect of a Polar Solvent on the1JCHSpin-coupling Constants in Chlorine-substituted Ethanes

1980 ◽  
Vol 53 (5) ◽  
pp. 1257-1262 ◽  
Author(s):  
Shosuke Watanabe ◽  
Isao Ando
Keyword(s):  
Polar Solvent ◽  
Coupling Constants

The solvent dependence of the small internal barrier to rotation in 3,5-dichlorobenzyl fluoride

1992 ◽  
Vol 70 (6) ◽  
pp. 1750-1753 ◽  
Author(s):  
Ted Schaefer ◽  
James R. Mansfield ◽  
Frank E. Hruska ◽  
Rudy Sebastian
Keyword(s):  
Polar Solvent ◽  
Coupling Constants ◽  
Side Chain ◽  
Parent Molecule ◽  
Nonpolar Medium ◽  
Solvent Dependence ◽  
Nuclear Magnetic Resonance Spectra ◽  
Conformational Properties ◽  
Free Molecules ◽  
Dichloro Derivative

The 1H and 19F nuclear magnetic resonance spectra of 3,5-dichlorobenzyl fluoride, dissolved in solvents of varying polarity, are analyzed to yield precise values of the long-range coupling constants between ring protons and the nuclei in the fluoromethyl group. The conformational properties of these coupling constants, dependent on the angle by which the C—H and C—F bonds of the side chain twist out of the aromatic plane, are used to determine the solvent dependence of the predominantly twofold barrier to rotation about the Csp2—Csp3 bond. In all solvents, the conformer in which the C—F bond lies in the aromatic plane represents the minimum in the internal rotational potential. The magnitude of the twofold potential changes from 3.2(2) kJ/mol in the nonpolar medium, C6D12, to 0.6(2) kJ/mol in the polar solvent, CD3CN. Intermediate magnitudes occur for solvents of intermediate dielectric constant. Comparisons are made with the parent molecule, benzyl fluoride, for which the perpendicular conformer is most stable in the same solvents. Such comparisons indicate that for the free molecules, the in-plane conformer of the dichloro derivative is also more stable than the same conformer of benzyl fluoride. This indication is in qualitative agreement with molecular orbital predictions.

The internal rotational potential in benzyl chloride

1986 ◽  
Vol 64 (7) ◽  
pp. 1322-1325
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian ◽  
Glenn H. Penner
Keyword(s):  
Internal Rotation ◽  
Long Range ◽  
Nmr Spectra ◽  
Benzyl Chloride ◽  
Polar Solvent ◽  
Low Energy ◽  
Coupling Constants ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
H Nmr

The 1H nmr spectra of benzyl chloride in dilute CS2 and acetone-d6 solutions are analyzed. The long-range coupling constants are consistent only with a low-energy conformation in which the C—Cl bond lies in a plane perpendicular to the benzene plane. Geometry optimized computations at the STO 3G level of molecular orbital theory agree with this conclusion and yield a nearly pure twofold barrier to internal rotation of 8.6 kJ/mol. In CS2 solution the long-range couplings yield 8.8 kJ/mol, rising to 11.2 kJ/mol in acetone solution. This increase in the internal barrier in a polar solvent is similar to that found for benzyl fluoride, but in the latter the barrier itself is very much smaller than in benzyl chloride.

Vibrational and thermal averaging of the indirect nuclear spin-spin coupling constants of CH4, SiH4, GeH4 and SnH4

1997 ◽  
Vol 91 (5) ◽  
pp. 897-907 ◽  
Author(s):  
SHEELA KIRPEKAR ◽  
THOMAS ENEVOLDSEN ◽  
JENS ODDERSHEDE ◽  
WILLIAM RAYNES
Keyword(s):  
Nuclear Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

$\mathit{Ab\!-\!initio}$ Determination of Magnetic Interface Coupling Constants for Magnetic Multilayers

1997 ◽  
Vol 7 (11) ◽  
pp. 1299-1304 ◽  
Author(s):  
P. Weinberger ◽  
C. Sommers ◽  
U. Pustogowa ◽  
L. Szunyogh ◽  
B. Újfalussy
Keyword(s):  
Ab Initio ◽  
Magnetic Multilayers ◽  
Coupling Constants ◽  
Interface Coupling

Characterization of non polar-polar solvent extracts from some tea plantation shade tree leaves with special reference to antioxidant and antibacterial activities

2020 ◽  
pp. 15-21
Author(s):  
Arindam Ghosh ◽  
Soumya Majumder ◽  
Sumedha Saha ◽  
Malay Bhattacharya
Keyword(s):  
Cardiac Glycosides ◽  
Polar Solvent ◽  
Reducing Power ◽  
Scavenging Activity ◽  
Shade Trees ◽  
Crude Fibre ◽  
Shade Tree ◽  
Dpph Scavenging Activity ◽  
Dpph Scavenging

Beneficial properties of shade trees of tea plantations other than their medicinal properties have been extensively studied. This research was initiated to explore the properties of some shade trees with special emphasis on their antioxidant and antibacterial properties. Leaves from shade tree like Dalbergia sissoo (DS), Cassia siamea (CS), Derris robusta (DR), Leucaena leucocephala (LL), Acacia lenticularis (AL) and Melia azedarach (MA) were used for the study. Characterization of shade tree leaves by determination of moisture, crude fibre and ash content and tests of non polar – polar solvent extracts for steroid, tannins, cardiac glycosides and coumarin, free radical scavenging, ferric reducing power, NO scavenging activities, quantification of Flavonoids and antibacterial activity were conducted. The average moisture, crude fibre and ash percentage of shade tree plants were found to be 62.95, 11.28 and 1.86 respectively. Methanol, ethanol, acetone and ethyl acetate respectively proved to be the most potent solvent for various phytochemical extractions as it gave positive results for tests like tannin, steroid, cardiac glycosides and coumarin. AL (91.46%), DR (92.69%), LL (94.32%) and MA (93.34%) leaf extracts showed a high level of DPPH scavenging activity in their water extracts. In DS (88.11%) and CS (83.23%) maximum DPPH scavenging activity was observed in Diethyl ether and Methanol extracts respectively.  Acetone extracts were more active than the water extracts in exhibiting ferric reducing power and NO scavenging activity. Summation of the quantity revealed that DS showed maximum presence of flavonoids and acetone as most potential for isolation of flavonoids. The decreasing order of summative antibacterial activity was recorded in DS, followed by CS, DR, AL, MA and LL. Chloroform showed the highest summative inhibition zone followed by ethanol, ethyl acetate, diethyl ether, acetone, water,  hexane, benzene and methanol. The antioxidant and antibacterial potential of shade trees were established.

The Malleable Excited States of Benzothiadiazole Dyes and Investigation of their Potential for Photochemical Control

2019 ◽  
Author(s):  
Caroline C. Warner ◽  
andrea thooft ◽  
Bryan J. Lampkin ◽  
selin demirci ◽  
Brett VanVeller
Keyword(s):  
Excited State ◽  
Excited States ◽  
Polar Solvent ◽  
Nonpolar Solvent ◽  
Photochemical Degradation ◽  
Solvent Lead ◽  
Environmentally Sensitive

<p>A strategy to control the efficiency of a photocleavage reaction based on changing the nature of the excited state is presented. A novel class of photoactive compounds has been synthesized by combining the classical o-nitrobenzyl scaffold with an environmentally sensitive dye, 4-amino-nitrobenzothiazole. Irradiation in a polar solvent lead to an excited state that is inoperative for photochemistry whereas excitation in a nonpolar solvent lead to an excited state that is photochemically active. A photochemical degradation appears to be the preferred process in contrast to the intended photocleavage process.</p>

Assessing the Calculation of Exchange Coupling Constants and Spin Crossover Gaps Using the Approximate Projection Model to Improve Density Function Calculations

2019 ◽  
Author(s):  
Xianghai Sheng ◽  
Lee Thompson ◽  
Hrant Hratchian
Keyword(s):  
Density Functional Theory ◽  
Exchange Coupling ◽  
Density Functional ◽  
Spin Crossover ◽  
Coupling Constants ◽  
Spin Projection ◽  
Coupling Constant ◽  
Projection Model ◽  
Functional Theory

This work evaluates the quality of exchange coupling constant and spin crossover gap calculations using density functional theory corrected by the Approximate Projection model. Results show that improvements using the Approximate Projection model range from modest to significant. This study demonstrates that, at least for the class of systems examined here, spin-projection generally improves the quality of density functional theory calculations of J-coupling constants and spin crossover gaps. Furthermore, it is shown that spin-projection can be important for both geometry optimization and energy evaluations. The Approximate Project model provides an affordable and practical approach for effectively correcting spin-contamination errors in molecular exchange coupling constant and spin crossover gap calculations.

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