Structure, thermodynamics, and electronic properties are predicted for a new low energy phase of carbon which contains planar sheets equally occupied by sp2 and sp carbon atoms. The isolated planar sheets have the same planar symmetry as do the layers in graphite (p6m) and can be formally viewed as resulting from the replacement of one‐third of the carbon–carbon bonds in graphite by –C 3/4 C– linkages. This material, called graphyne, is predicted to have a crystalline state formation energy of 12.4 kcal/mol carbon, which appears to be much lower than for any carbon phase which contains acetylenic groups as a major structural component. Based on the major structural reorganization required for graphitization and the observed high temperature stability of known model compounds, high temperature stability is predicted for graphyne. While graphyne will have similar mechanical properties as graphite, it is predicted to be a large bandgap semiconductor (Eg=1.2 eV) rather than a metal or semimetal. Based on this...

Structure‐property predictions for new planar forms of carbon: Layered phases containing sp2 and sp atoms

In recent years our research group has made a systematic effort to study the validity of transition state theory (TST). We have found that the conventional theory is sometimes remarkably accurate, but in many other cases it leads to large errors. Fortunately we have found that a much more reliable theory that has many of the advantages of conventional TST can also be formulated, and it can be applied to practical problems with an effort that is much closer to that required for conventional transition state theory than to that required for quantal dynamics calculations. The two most important features in the improved approach to transition state theory state theory are the variational determination of the transition state and the incorporation of tunneling contributions by multidimensional semiclassical approximations. 13 refs.

/pdf/variational-transition-state-theory-ajp35t2n6n.pdf

Variational Transition State Theory

Anisotropy of the Induced Current Density (ACID), a General Method To Quantify and Visualize Electronic Delocalization

The activation strain or distortion/interaction model is a tool to analyze activation barriers that determine reaction rates. For bimolecular reactions, the activation energies are the sum of the energies to distort the reactants into geometries they have in transition states plus the interaction energies between the two distorted molecules. The energy required to distort the molecules is called the activation strain or distortion energy. This energy is the principal contributor to the activation barrier. The transition state occurs when this activation strain is overcome by the stabilizing interaction energy. Following the changes in these energies along the reaction coordinate gives insights into the factors controlling reactivity. This model has been applied to reactions of all types in both organic and inorganic chemistry, including substitutions and eliminations, cycloadditions, and several types of organometallic reactions.

/pdf/analyzing-reaction-rates-with-the-distortion-interaction-46v7zu57ma.pdf

Analyzing Reaction Rates with the Distortion/Interaction‐Activation Strain Model

Within the wr-orbital axis vector theory, the total rehybridization required for closure of the fullerenes is approximately conserved. This result allows the development of a structure-based index of strain in the fullerenes, and it is estimated that about 80 percent of the heat of formation of the carbon atoms in C60 may be attributed to a combination of v strain and steric inhibition of resonance. Application of this analysis to the geometries of structurally characterized organometallic derivatives of C60 and C70 shows that the reactivity exhibited by the fullerenes may be attributed to the relief of a combination of local and global strain energy. C60 is of ambiguous aromatic character with anomalous magnetic properties but with the reactivity of a continuous aromatic molecule, moderated only by the tremendous strain inherent in the spheroidal structure.

https://science.sciencemag.org/content/sci/261/5128/1545.full.pdf

Robert W. Strozier

Papers

Barriers to thermally allowed reactions and the elusiveness of neutral homoaromaticity

Influence of molecular distortions upon reactivity and stereochemistry in nucleophilic additions to acetylenes

Influence of molecular distortions upon reactivity and stereochemistry in nucleophilic additions to acetylenes

Regioselectivity of nitrile oxide cycloadditions to electron-deficient dipolarophiles

Barriers to thermally allowed reactions and the elusiveness of neutral homoaromaticity