ChemInform Abstract: NMR Spectroscopy and Cyclic Voltammetry of N-Aryl-P,P,P-triphenylphospha-λ5-azenes, Substituent Effects and Correlation with Molecular Orbital Calculations.

Abstract Optimized geometrical parameters, electron densities, heats of formation and stabilization energies have been obtained on X-substituted phenylallyl alcohols, where X is H, OCH3, NH2, CN, F and CH3 at ortho, meta, and para positions, using MINDO-Forces SCF-molecular orbital calculations. The substituent effects on the geometrical parameters and the electron density are discussed.

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An investigation into the origins of polar substituent effects upon 19F chemical shifts, using 4-substituted β,β-difluorostyrenes

Canadian Journal of Chemistry ◽

10.1139/v80-130 ◽

1980 ◽

Vol 58 (8) ◽

pp. 839-845 ◽

Cited By ~ 20

Author(s):

William F. Reynolds ◽

Victoria G. Gibb ◽

Nick Plavac

Keyword(s):

Chemical Shift ◽

Electron Density ◽

Molecular Orbital ◽

Excellent Agreement ◽

Field Effect ◽

Chemical Shifts ◽

Substituent Effects ◽

Molecular Orbital Calculations ◽

Chemical Shift Difference ◽

Polar Substituent

19F, 13C, and 1H chemical shifts have been determined for β,β-difluorostyrene and eight 4-substituted derivatives. The β-fluorine chemical shift difference, ΔδF, is used to evaluate the constant in the Buckingham equation. A = 3.0 × 10−11 esu for C—F bonds which is in excellent agreement with the value derived by Adcock and Khor. This allows accurate estimates of direct field effect contributions to 19F chemical shifts in aryl fluorides. Substituent parameter correlations demonstrate that the primary polar effect on 19F chemical shifts is field-induced π polarization. Abinitio molecular orbital calculations confirm that the substituent-induced 19F chemical shifts reflect changes in fluorine π electron density.

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1H nuclear magnetic resonance and molecular orbital studies of the conformations of 3-fluoroanisole

Canadian Journal of Chemistry ◽

10.1139/v89-156 ◽

1989 ◽

Vol 67 (6) ◽

pp. 1027-1031 ◽

Cited By ~ 8

Author(s):

Ted Schaefer ◽

Rudy Sebastian

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Molecular Orbital ◽

Substituent Effects ◽

Spin Coupling ◽

Basis Set ◽

Molecular Orbital Calculations ◽

Minimal Basis ◽

Parent Molecule ◽

Nuclear Magnetic

The proximate spin–spin coupling constant between the methyl protons and the ring protons, 5J(H,OCH3), is extracted from a full analysis of the 1H and 19F nuclear magnetic resonance spectra of 3-fluoroanisole in CS2 and acetone-d6 solutions. The values of 5J(H,OCH3) imply that the less polar cis conformer is slightly more stable at 300 K than the more polar trans conformer in both solvents, in agreement with geometry-optimized STO-3G MO computations for the free molecule. The latter also find a higher barrier to internal rotation of the methoxy group for 3-fluoroanisole than for the parent molecule. The present results are compared with other measurements of the conformer ratio for the vapor and for solutions. The STO-3G and 6-31G structures of the cis and trans conformers are compared. The C—F bond length is computed more reliably with the minimal basis set, as is the COC bond angle. The internal angles of the benzene moiety are, of course, found more accurately with the 6-31G basis. The computations indicate additivity of the substituent effects on the internal angle, as found experimentally for a variety of benzene derivatives. Keywords: 1H NMR of fluoroanisole, conformations of fluoroanisole, molecular orbital calculations for fluoroanisole.

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Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. II. 4-Substituted α-Methylstyrenes and α-t-Butylstyrenes

Canadian Journal of Chemistry ◽

10.1139/v73-390 ◽

1973 ◽

Vol 51 (15) ◽

pp. 2596-2596 ◽

Cited By ~ 1

Author(s):

G. K. Hamer ◽

I. R. Peat ◽

W. F. Reynolds

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Magnetic Resonance Spectroscopy ◽

Nuclear Magnetic Resonance Spectroscopy ◽

Molecular Orbital ◽

Valence Electron ◽

Substituent Effects ◽

Resonance Spectroscopy ◽

Molecular Orbital Calculations ◽

Nuclear Magnetic

not available

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Comparative Cumulene Substituent Effects: Ketenes, Allenes, Diazomethanes, Diazirines, and Cyclopropenes by ab Initio Molecular Orbital Calculations

The Journal of Organic Chemistry ◽

10.1021/jo00095a028 ◽

1994 ◽

Vol 59 (16) ◽

pp. 4506-4515 ◽

Cited By ~ 29

Author(s):

Michael A. McAllister ◽

Thomas T. Tidwell

Keyword(s):

Ab Initio ◽

Molecular Orbital ◽

Substituent Effects ◽

Molecular Orbital Calculations

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NMR Spectroscopy and Molecular Orbital Calculations to Interpret the Mutagenicity of Nitrobenzanthrones

Polycyclic Aromatic Compounds ◽

10.1080/10406630008034723 ◽

2001 ◽

Vol 19 (1-4) ◽

pp. 73-81 ◽

Cited By ~ 1

Author(s):

Yohko Sakamoto ◽

Shigeru Ohshima ◽

Takeji Enya ◽

Hitomi Suzuki ◽

Yoshiharu Hisamatsu

Keyword(s):

Nmr Spectroscopy ◽

Molecular Orbital ◽

Molecular Orbital Calculations

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Substituent effects at silicon in cations SiX+, HSiX+•, and H2SiX+, and in radicals H2SiX+•

Canadian Journal of Chemistry ◽

10.1139/v89-151 ◽

1989 ◽

Vol 67 (6) ◽

pp. 991-997 ◽

Cited By ~ 10

Author(s):

A. C. Hopkinson ◽

M. H. Lien

Keyword(s):

Linear Relationship ◽

Molecular Orbital ◽

Single Point ◽

Substituent Effects ◽

Molecular Orbital Calculations ◽

Amino Group ◽

Ionisation Potential ◽

Silyl Radicals

Abinitio molecular orbital calculations at the 6-31G* level have been used to optimise structures for ions SiX+, HSiX+•, and H2SiX+, and for neutrals HSiX (singlets), H2SiX•, and H3SiX, where X is H, CH3, NH2, OH, F, CN, and NC. Single point calculations at the MP4(SDTQ)/6-31G* level were used to calculate substituent stabilisation energies.The amino group is the strongest π-donor and also is the most stabilising group in the cations, the silylenes, and the silyl radicals. Stabilisation is greatest in ions SiX+. Ions HSiX+• and H2SiX+ are stabilised by similar but smaller amounts, although CN and NC are destabilising in these ions. Substituent stabilisation energies in radicals H2SiX• are almost zero. There is a linear relationship between the stabilisation energies of ions H2SiX+ and the ionisation potentials of radicals H2SiX•, but a similar plot correlating stabilisation energies for ions HSiX+۟• with the ionisation potential of HSiX (singlet) shows considerable scatter. Keywords: silications, silyl radicals, stabilisation energies.

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