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A Ni/photoredox-catalyzed enantioselective reductive coupling of styrene oxides and aryl iodides is reported. This reaction affords access to enantioenriched 2,2-diarylalcohols from racemic epoxides via a stereoconvergent mechanism. Multivariate linear regression (MVLR) analysis with 29 bioxazoline (BiOx) and biimidazoline (BiIm) ligands revealed that enantioselectivity correlates with electronic properties of the ligands, with more electron-donating ligands affording higher ee's. Experimental and computational mechanistic studies were conducted, lending support to the hypothesis that reductive elimination is enantiodetermining and the electronic character of the ligands influences the enantioselectivity by altering the position of the transition state structure along the reaction coordinate. This study demonstrates the benefits of utilizing statistical modeling as a platform for mechanistic understanding and provides new insight into an emerging class of chiral ligands for stereoconvergent Ni and Ni/photoredox cross-coupling.

The radical anion of the highly pyramidalized alkene 1,5-dehydroquadricyclane is generated in the gas phase from the Squires reaction of 1,5-bis(trimethylsilyl)quadricyclane with F(super -)/F2. The experimental heat of hydrogenation of 1,5-dehydroquadricyclane, obtained from a thermochemical cycle, is found to be 91 (plusmn) 9 kcal/mol.

The effects of one or two phenyl substituents on the activation enthalpy for a 1,5-hydrogen shift in 3-(Z)-1,3-pentadiene (1) and on the geometry of the transition structure (TS) is investigated by B3LYP/6-31G calculations. The difference between steric effects in the transoid isomers of the reactants is factored out by comparing the activation enthalpies in the cisoid conformers.

The effect of 2,2-ethylene-ketal functionality on the singlet-triplet energy gap and on the first electronic transition in singlet cyclopentane-1,3 dilys is investigated. The calculations and experiments show a new type of substituent effect, and provide a definitive assignment of the lowest energy electronic transition in the singlet diradicals.

A second-generation synthesis of the C1-C28 segment that has yielded almost 10 grams of the intermediate and the incorporation of this building block in a total synthesis of altohyrtin C is presented. Anti-aldol coupling is used to join AB and CD fragments.

The Lawesson reagent and P2S5 mediated reductive coupling of phenalenone leading to peropyrene and the mechanism of the reaction is reported. 1,1'-biphenalenylidene, a bistricyclic aromatic ene (BAE) with a topology different from that of conventional BAEs is found to have a diradical structure.

Results of calculations carried out on the singlet-triplet energy differences in monocyclic diradicals are reported. The size of the singlet-triplet energy gap increases with the electron donating ability of the substituents in the symmetrically para-disubstituted diradicals.

The struggle of protein of oligoether self-assembled monolayers (SAMs) against the gold and silver surfaces is studied in proper order to expose the compositional elements which indicate if a SAM is in a position to fight the protein adsorption. Finally, it is identified that the internal and terminal hydrophilicity support the protein's struggle of an oligoether monolayer.

Detailed analysis is presented about the photochemistry of ortho-biphenyl azide with the help of the laser flash photolysis along with the UV-vis and the IR identification technique of the temporary mediators. Moreover, the power of the temporary mediators and that of the temporary formations that link them are effectively envisaged by the calculation of CASPT2 divided by the 6-31G.

The relative energies of the Cs and C2v geometries of several 1,5-disubstituted semibullvalences are examined. It is found that the destabilization of the Cs geometries of semibullvalences leads to a decrease in the amount of bishomoaromatic stabilization of the C2v geometries.

(8/8) CASSCF and (8/8) CASPT2 calculations are performed in order to investigate the potential surface for the ring expansion of the (super1) A(sub2) state of phenlphosphinidene to 1phospha-1,2,4,6-cycloheptatetraene. Unlike the comparable ring expansion of the (super1) A(sub2) state of phenylnitrene to 1-aza-1,2,4,6-cycloheptatetraene, ring expansion is computed to be quite endothermic.

Degenerate hydrogen atom exchange reactions are studied using calculations, based on density functional theory (DFT), for benzyl radical plus toluene, phenoxyl radical plus phenol, and methoxyl radical plus methanol. The calculations found that benzyl/toluene and methoxyl/methanol undergo hydrogen exchange by an hydrogen atom transfer (HAT) mechanism, but that phenoxyl/phenol reacts by a proton-coupled electron transfer (PCET) mechanism.

A study demonstrates that horseradish peroxidase (HRP) catalyzes the formation of nitric oxide (NO) from the clinically used drug hydroxyurea. The results indicate that peroxidase-cataylsed nitric oxide (NO) release form hydroxy urea could play an important role in the overall pharmacological properties of the drug.

The synthesis of the first molecule is stimulated that will be found to display neutral bishomoromaticity at its equilibrium geometry. The CN stretching frequencies computed for the C2 geometry of 1,5-dimethyl-2,6-dicyano-4,8-diphenylsemibullvalene(super deloc), fit the low frequency absorptions seen in the infrared spectrum of 1,5-dimethyl-2,6-dicyano-4,8-diphenylsemibullvalene, thus furnishing independent evidence that bishomoaromatic geometries of sembullvalenes have, in fact, are observed spectroscopically.

Research describing the ring inversion and cleavage of bicyclo(2.2.0)hexane is presented. The paper shows that all three of the reactions studied produce a twist-boat diradical intermediate.

Research is presented describing the study of octanitrochubane nitro group chemicals to determine interactions using computational analysis.

B3LYP/6-31G calculations were undertaken on Cope rearrangements of 1,5-hexadienes.

CASSCF and CASPT2 calculations were undertaken finding that a singlet methylnitrene is an energy minimum and not a transition state.

B3LYP/6-31G calculations were performed on the chair Cope rearrangements of a range of substituted 1,5-hexadienes.

A study performed ab initio calculations of the potential energy surfaces for the stereomutations of spiropentane and cis- and trans-dimethylspiropentanes. The analysis aimed to better elucidate why disrotation is apparently preferred to conrotation in the pyrolyses of both the 1,2-dimethyl- and 1,2,4-trimethylspiropentanes. It also investigated why double rotation of C-1 and C-2 in the trans-1,2,4-trimethylspiropentanes is slower than epimerization at C-4. Results are discussed.

Experiments were performed to investigate the Cope rearrangement in 1,2,6 heptatriene (1) to 3-methylene-1,5,hexadiene (3). CASPT2 and UB3LYP calculations describing the potential energy surface for the Cope rearrangement of 1 to 3 were performed. Two different pathways which converged on a common transition state were identified. The pathways on the potential energy surface led to the formation of a diradical intermediate or directly to the product which explain the conclusions in several oxygen-trapping experiments.

Research was conducted to examine the isotope effects on the ring inversion of cyclooctatetraene using proton magnetic resonance spectroscopy (1H NMR). 1H NMR studies reveal an inverse isotope influence on the rate of ring inversion of k(sub H)/k(sub D) = 0.68-0.57 in temperatures ranging from -10 to -50 degrees C. Results provide strong evidence for the computationally based explanation of the difference between the small inverse, equilibrium isotope effect calculated for reduction of COT and the large normal equilibrium isotope influence for reduction of planar aromatic molecules.

The effects of geminal silyl substituents on the stereomutation of cyclopropane and on the singlet-triplet splitting in trimethylene were examined using ab initio calculations. After correction for zero point energy differences, singlet trimethylene diradical was found to be an energy minimum. Coupled conrotation of C(2) and C(3) is expected to dominate rotation of just one of the methylene groups in the stereomutation of 1,1-disilylcyclopropane.

Ab initio studies were conducted to investigate the stability of nitrenes and carbenes. Results indicated that triplet nitrenes were more thermodynamically stable than comparable triplet carbenes. It was also observed that the energy differences between the singlets were large enough to explain the reversibility of the ring expansion of singlet phenylnitrine and the exothermic process seen in the singlet phenylcarbene.

Density functional calculations on B3LYP6F-31+G have been conducted to provide an explanation of the different equilibrium isotope effects which are evident in the reductions of cyclooctatetraene (COT-8) and benzene-d6. The calculations and observations reveal that the reduction of planar COT.- also generated a substantial, equilibrium isotope effect which is due to an inverse isotope effect on the planarization of COT's tub-shaped ring.

Multiconfigurational methods and the inclusion of dynamic electron correlation were used to perform ab initio calculations on 1,3,5-trimethylenebenzene and its negative ion. The ground state of 1,3,5-tirmethylbenzene was found to be the high spin 4A1' with a D3h symetry. The lowest energy excited is 2E' in D3h symmetry which is subject to first-order Jahn-Teller distortions to geometries of lower symmetry.

The introduction of each trigonal center into a cyclopropane ring and its effect in the strain energy was investigated through ab initio calculations. Results have demontrated that the introduction of a trigonal center into a three-membered ring produces an additional strain. The results further demonstrated that the resulting strain was not secondary to the increase in angle strain but the loss of a strong cyclopropane bond.

The homoaromatic characteristics of strained semibullvalenes were established through analyses of high level ab initio and density functional theory aided by UV and 13C NMR spectral studies. Results have shown that the C2 v symmetric transition structure for the Cope rearrangement in the parent semibullvalene was bishomoaromatic. However, the 4,6-ethanosemibullvalene was localized and not homoaromatic.

The ring expansion reactions of several fluorinated arylnitrenes were analyzed computationally at the CASPT2N/cc-pVDZ//CASSCF(8,8)/6-31G* + ZPE level of theory to investigate the dramatic difference in reactivity between phenylnitrene (1a) and pentafluorophenylnitrene (1b). In all cases, ring expansion of the open-shell singlet nitrenes (1) to the ketenimines (3) was computed to occur through the same two-step process as that predicted for the parent system (1a), with the first step, cyclization to the azirines (2), being rate-determining.

The rearrangement of singlet phenylnitrene (1a) to 1-azacyclohepta-1,2,4,6-tetraene (3a) was investigated computationally, employing the CASSCF and CASPT2N techniques in conjunction with the 6-31G*, cc-pVDZ and 6-311G-(2d,p) basis sets. Findings revealed that ring expansion of 1A2 1a to 3a occurs through an intermediate, 7-azabicyclo(4.1.0)hepta-2,4,6-triene. The first step of the rearrangement is expected to have a barrier of ca. 6 kcal/mol and to be the rate-determining step.

Ab initio calculations and kinetic method measurements confirmed the expectation that the relief of olefin strain energy associated with protonation of tricyclo(3.3.3.0(super 3,7))undec-3(7)-ene will lead to a significantly greater proton affinity (PA) for it, compared with bicyclo(3.3.0)oct-1(5)-ene. This was found in an investigation of the effects of alkene pyramidalization on PA, using tricyclo(3.3.3.0(super 3,7))undec-3(7)-ene with bicyclo(3.3.0)oct-1(5)-ene as reference compound. Ab initio calculations, however, revealed a smaller PA difference between the two compounds than experiments which show a difference of 23 +/- 2 kcal/mol.

The photoelectron spectra of isomers of C7H7- ions determine the electron affinities of the corresponding C7H7 radicals. Deprotonation of quadricyclane by an amide ion occurs at two sites having different electron affinities. The photoelectron spectra of deprotonation in norbornadiene at one site shows that the ground and excited states result from sigma and pi-orbitals, respectively. Deprotonation of 1,6-heptadiyene occurs at the terminal and the third carbon atoms. Cycloheptatriene on deprotonation at methylene group shows a signal at a low binding energy.

The energy difference between bicyclo(n.1.0)alkanones, where n is equal to 1-3, and the isomeric 2-cycloalkanone-1,3-diyls is calculated. The effects of the carbonyl groups in the first series of alkanones on the energies required for ring opening are studied. The effects of alkyl substituents at the bridgehead cartons are determined. Results indicate the presence of experimental barriers to ring iversion.

Ab initio calculations were used to analyze the rates of beta-cleavage reactions in cubylcarbinyl and homocubyl radicals. These polycyclic radicals exhibit an excellent Bell-Evans-Polanyi relationship between the heat of reaction (delta-H) and the rate constant (Ea). The antibonding association between the two atomic orbitals (AOs), while these radicals are undergoing beta-cleavage reactions, has a minute impact on the transition state energies.

The initial calculations on m-benzoquinodimethane and m-phenylene bis(nitroxide) reveal that at the dihedral angles of phi = 90 degrees between the benzene ring and the radical-containing groups, the ground state changes from the singlet to the triplet. A selective destabilization of the antisymmetric combination of the radical centers with single electron occurs by a sigma orbital of the symmetry on the m-phenylene coupler. This destabilization causes the alteration of the m-phenylene from a ferromagnetic coupler to an antiferromagnetic coupler.

6-31G* basis set-based CASSCF and CASPT2N calculations of the UV-visible spectrum of1,2,4,5-tetramethylenebenzene reveals pi-pi and sigma-pi correlations. Excitation energies associated with the 1(1)A(g) excited state control the spectrum, which occurs due to a diradical. The longest-wavelength absorption in the spectrum occurs due to a 1(1)A(g) to 2(1)A(g) transition. The results imply that the disjoint radical has a singlet ground state and violate Hund's rule.

Kinetic method is employed to calculate the proton affinity of phenoxy radical and the results agree with the results of FT-ICR bracketing experiments and thermochemical cycle. This method is extended for substituted phenoxy radicals and isomeric radicals. The proton affinities of isomeric radicals are higher than those of the phenoxy radicals and are due to a thermodynamic stabilization of the product.

Monte Carlo simulations at 25 degrees centigrade were used to compute solvent effects on the disrotatory ring of cyclopropanone and 2, 2-dimethylcyclopropanone oxyallyls, which were intermediates in cyclopropanone stereomutations, associated with the transition states for the ring openings. These oxyallyls were diradical rather than zwitterionic.

GVB and SD-SI studies predict that germinal fluorines' presence in 1,1-difluorocyclopropane may increase the coupled methylene streomutation and alter the ring opening and closure stereochemistry from conrotatory to disrotatory. The alkyl substituents increase the preference for coupled rotation and make the singlet to be present below the triplet in 2,2-difluorotrimethylene.

CASPT2N studies of chair and boat Cope rearrangements using the 6-31G*, 6-311G**, and 6-311G(2d,2p) basis sets yield a single C2h symmetry stationary point for the chair and C2v symmetry for the boat for a synchronized bond-making and -breaking reaction. CASPT2N yields greater energetics than the estimated CASSCP level.

Analyses of o-didehydrobenzene (1) provided a singlet-triplet energy difference which were slightly lower than earlier estimates. The energy differences between the singlet ground state of 1 and those of the meta 2 and para 3 isomers are greater than the values for the differences between the heats of formation derived earlier. This was done by performing CI computations with the 6-311G basis set on 1.

A study was done on the rotational barriers to 1,1-difluoroallyl radical using ab initio calculations. Results show that the CF2 group pyramidalization makes the barrier to CF2 rotation in 1,1,3,3-tetrafluoroallyl radical less than in the parent allyl radical. It also lessens the pi bond energy of tetrafluoroethylene compared to ethylene. In addition, calculations show that the intrinsic strength of the pi bond in 1, 1-difluoroethylene is greater by 9-10 kcal/mol than the strength of the pi bond in ethylene.

Ab initio studies, using sigma-S pi-SDCI optimization, reveal why m-quinone should exist as a triplet in the ground state. The behavior of m-quinone differs from that of 2,4-cyclobutadiene in the that latter changes from a triplet to a singlet ingoing from a dimethylene to a dioxo species. Based on a lower triplet energy value compared to the lowest singlet energy, the study notes that the lowest singlet state of m-quinone exhibits little pi-bonding between the exocyclic CH2and the ring, in contrast to that of 2,4-dimethylcyclobutane. This difference explains the inability of methylene- oxygen substitution to change m-quinone from a triplet to a singlet.

Calculations at the CI-SD level with the 6-31 G* basis set are performed to elucidate the effect of an adjacent pi bond on the A-H bond dissociation energy in X-AH3, where A = C or Si. The systems studied involve replacing X = H3C- by X = H2C=CH- and H2Si=CH- and replacing X = H3Si- by X = H2C=SiH- and H2Si=SiH-. Conjugative stabilization energies of the generated allylic radicals are derived from the energies computed to be needed to distort a terminal AH2 radical group out of conjugation.

Ab initio calculations were used to determine the transition state sites, vibrational force constants and isotopic substitution effects in cyclopropane stereomutations. Related energy values were estimated at the GVB/6-31G* optimized geometries and SD-CI levels. Results showed that the conrotatory double rotation was 0.97 kilocalories/molecule higher than single rotation at the GVB level. However, analysis of the SD-CI data indicated that the introduction of additional electron correlation relatively raised the observed value.