Orbital interactions. IX. The effect of remote substituents on the electrophilic nitration of a series of 11-substituted exo-hexahydro-7,10-methanofluoranthenes

1980 ◽  
Vol 33 (4) ◽  
pp. 795 ◽  
Author(s):  
MJ Oliver ◽  
HK Patney ◽  
MN Paddon-Row
Keyword(s):  
Product Distribution ◽  
Molecular Orbitals ◽  
Orbital Interactions ◽  
Opposite Result ◽  
Field Effects ◽  
Methoxy Substituent ◽  
Salient Features ◽  
Scf Calculations

Product distribution and the relative rates of nitration (Cu(NO3)2,3H2O/Ac2O) of a series of 11-substituted exo-hexahydro-7,10- methanofluoranthenes, (8), (9b), (10) and (11b), and acenaphthene, (12), have been determined. It was observed that a syn-methoxy substituent, as in (11b), greatly enhanced the reactivity of the acenaphthene ring towards nitration compared with unsubstituted (8), the α position being activated more than the γ position. Precisely the opposite result was obtained for the nitration of the ketone (10). These results are explained in terms of the consequences of through- space orbital interactions (OITS), operating between the molecular orbitals of the 11-substituent and those of the acenaphthene ring; a PMO model is used for the nitration reaction. The results of INDO MO SCF calculations on the water-acenaphthene complex (22) and the formaldehyde-acenaphthene complex (23), which are intended to mimic the salient features of (11b) and (10) respectively, lend support to the OITS proposal. However, alternative proposals, based on field effects (in the case of (10)) and on the formation of a complex (24) for the nitration of (11b), are also discussed.

A comparative theoretical study of the electronic structure of some nickel(II) azides, thiocyanates, and isothiocyanates

1998 ◽  
Vol 76 (7) ◽  
pp. 1006-1014 ◽  
Author(s):  
R H Abu-Eittah ◽  
M El-Esawy ◽  
N Ghoneim ◽  
A T Aly
Keyword(s):  
Electronic Structure ◽  
Electronic Structures ◽  
Theoretical Study ◽  
Molecular Orbitals ◽  
Basis Sets ◽  
Theoretical Treatment ◽  
Double Zeta ◽  
Experimental Values ◽  
Scf Calculations ◽  
Split Valence

The electronic structure, conformation, and molecular orbitals of some nickel(II) azides, thiocyanates, and isothiocyanates have been studied. Three different basis sets: split valence (SV), split valence with six d-Gaussians (SV6D), and double zeta (DZ) sets, were used to find the best ground state for nickel. It has been found that the combination, DZ-3F, gives results closest to the experimental values. The electronic structures of the nickel azides studied were completely different from those of the nickel thiocyanates. On the other hand, the electronic structures of the nickel thiocyanates studied were highly comparable to those of the corresponding nickel isothiocyanates. Molecular orbitals were computed for the complexes studied and the types of electronic transitions expected were identified and discussed.Key words: Ni(II) azides, thiocyanates, and isothiocyanates: ab initio SCF calculations; MO calculations on some Ni(II) complexes; theoretical treatment of some Ni(II) ions and salts; geometry and energetics of some nickel(II) azides, thiocyanates, and isothiocyanates.

A Photoelectron Investigation of the Peroxide Bond

1975 ◽  
Vol 53 (22) ◽  
pp. 3439-3447 ◽  
Author(s):  
R. S. Brown
Keyword(s):  
Dihedral Angle ◽  
Ground State ◽  
Vibrational Frequencies ◽  
Molecular Orbitals ◽  
Photoelectron Spectra ◽  
Raman Spectroscopic ◽  
Orbital Interactions ◽  
Highest Occupied Molecular Orbitals ◽  
Peroxide Bond

The photoelectron spectra of several peroxides and their interpretation is presented. The effects of substituents is separated from vicinal orbital interactions using as a guideline the effect of similar substitution on the ether analogues. It is found that by comparison of Raman spectroscopic frequencies of the peroxide ground state, and vibrational frequencies for the ion (via pes), that the HOMO of peroxides is antibonding with respect to the O—O linkage. Additionally, the dependence of the splitting of the two highest occupied molecular orbitals on dihedral angle is verified by the pe spectra of several well-defined cyclic peroxides. Finally, the pe spectrum of tetramethyl-1,2-dioxacyclobutane (tetramethyl dioxetane) is presented indicating that it is not unlike other cyclic peroxides.

Orbital interactions. X. The effect of remote substituents on the electrophilic bromination of a series of stereoisomeric 9-substitutedhexahydro-l,4-methanobiphenylenes

1980 ◽  
Vol 33 (7) ◽  
pp. 1493 ◽  
Author(s):  
MN Paddon-Row ◽  
BV Lap ◽  
HK Patney ◽  
RN Warrener
Keyword(s):  
Carbon Atom ◽  
Methyl Ether ◽  
Electrostatic Field ◽  
Positive Charge ◽  
Carbonyl Carbon Atom ◽  
Carbonyl Carbon ◽  
Electrophilic Attack ◽  
Orbital Interactions ◽  
Electrophilic Bromination ◽  
Scf Calculations

A series of stereoisomeric 9-substituted hexahydro-1,4- methanobiphenylenes, (4)-(10),were synthesized and their products and relative rates of bromination (Br2/AcOH) determined. Bromination occurred exclusively at the 6-position to give compounds (16) and (17). The syn-methyl ether (5) was found to be at least 3 × 105 times more reactive than the corresponding ketone (7) in the exo-fused series. With the aid of INDO MO SCF calculations it was concluded that: (a) the enhanced reactivity of syn-methyl ether (5) compared with the parent hydrocarbon (4) is a consequence of orbital interactions through space; (b) of the 2000-fold diminished reactivity of ketone (7) compared with the parent hydrocarbon (4), a factor of 40 may be attributed to inductive and orbital interactions through bond effects; the residual factor of 50 is due largely to (repulsive) electrostatic field effects operating between the carbonyl carbon atom and the developing positive charge on the aromatic ring during electrophilic attack.

scholarly journals Magnetic field effects in chemical systems

2009 ◽  
Vol 81 (1) ◽  
pp. 19-43 ◽  
Author(s):  
Christopher T. Rodgers
Keyword(s):  
Magnetic Field ◽  
Radical Pair ◽  
Product Distribution ◽  
Radical Pair Mechanism ◽  
Magnetic Field Effects ◽  
Chemical Systems ◽  
Spin Chemistry ◽  
Radical Intermediates ◽  
Field Effects ◽  
Recent Developments

Chemical reactions that involve radical intermediates can be influenced by magnetic fields, which act to alter their rate, yield, or product distribution. These effects have been studied extensively in liquids, solids, and constrained media such as micelles. They may be interpreted using the radical pair mechanism (RPM). Such effects are central to the field of spin chemistry of which there have been several detailed and extensive reviews. This review instead presents an introductory account of the field of spin chemistry, suitable for use by graduate students or researchers who are new to the area. It proceeds by giving a brief historical overview of the development of spin chemistry, before introducing the essential theory. This is then illustrated by application to a series of recent developments in solution-phase magnetic field effects (MFEs). The closing pages of this review describe the role played by spin chemistry in the remarkable magnetic compass sense of birds and other animals.

Orbital interactions. VIII. Competition kinetic measurements of the Birch reduction of some compounds having the bicyclo[2,2,1]heptadiene framework as a means of investigating orbital interactions through space in these systems

1980 ◽  
Vol 33 (4) ◽  
pp. 785 ◽  
Author(s):  
MN Paddon-Row ◽  
R Hartcher
Keyword(s):  
Rate Constants ◽  
Relative Rate ◽  
Butyl Alcohol ◽  
Molecular Orbitals ◽  
Kinetic Measurements ◽  
Birch Reduction ◽  
Orbital Interactions ◽  
Relative Rate Constants ◽  
Lowest Unoccupied Molecular Orbitals

Relative rate constants for the Birch reduction (Li/liq. NH3/t-butyl alcohol) of norbornadiene (1),1,4-dihydro-1,4-methanonaphthalene (3), 9-(1-methylethylidene)-1,4-dihydro-1,4-methanonaphthalene(5), 1,4- dihydro-1,4-epoxynaphthalene (7), lithium benzoate, α-methylstyrene, and the hexahydrobenzenomethanoanthracene(20a), were obtained and compared with that obtained for the reduction of norbornene from an earlier study. Compounds (1), (3) and (5) were some 105 times more readily reduced than norbornene. These results are best explained in terms of the presence of through-space interactions operating between the two lowest unoccupied molecular orbitals in these molecules. The Birch reduction of (7) gave mainly 1,4-dihydronaphthalene (17).A mechanism for this reaction is presented.

Inter-Cage Orbital Interactions in [2+2] and [4+4] Dimers of Buckminsterfullerene

1994 ◽  
Vol 359 ◽  
Author(s):  
Shūichi Ōsawa ◽  
Eiji Ōsawa
Keyword(s):  
Geometry Optimization ◽  
Molecular Orbitals ◽  
Orbital Interaction ◽  
Orbital Interactions

ABSTRACTGeometry optimization of [2+2]- and [4+4]-dimers of C60 by semiempirical AMI MO method reveals usual length for the bridge bonds of the former but unusually long bonds for the latter. Perturbational analysis of molecular orbitals confirm the presence of orbital interaction through bond (OITB) between the cages in the [2+2] dimer but no interaction in the [4+4] dimer. These results contradict with previous examples of OITB wherein elongation of the mediating σ bond is usually observed.

Molecular orbitals from group orbitals. IX. The problem of hybrid lone pairs

1979 ◽  
Vol 57 (7) ◽  
pp. 729-732 ◽  
Author(s):  
Daniel Kost ◽  
H. Bernhard Schlegel ◽  
David John Mitchell ◽  
Saul Wolfe
Keyword(s):  
Ab Initio ◽  
Molecular Orbitals ◽  
Congeneric Species ◽  
Matrix Elements ◽  
Orbital Interactions ◽  
Lone Pairs ◽  
Conformational Properties ◽  
Group Orbitals

The quantitative PMO analysis of the ab initio wavefunction of a molecule A—B is based upon a partitioning of the Fock matrix elements of this wavefunction to obtain the fragments A and B, followed by computation of the stabilizing and destabilizing orbital interactions between the orbitals of these fragments that contribute to the HOMO of A—B. However, when one or both of the fragments is NH2 or a congeneric species, neither the 3a1 nor the 1b1 orbital of this fragment is appropriate for overlap with the second fragment, and the PMO analysis cannot be performed. A solution to this problem is proposed, and has been tested by application to various conformational properties of methylamine.

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