Howard E. Simmons

Pariser—Parr Theory: Quantum Mechanical Integrals from the Benzene Spectrum

The integrals which occur in Pariser—Parr ASMO—CI theory for carbon atoms at short internuclear distances (≤2.40 A) can be derived from the spectrum of benzene [R. Pariser, J. Chem. Phys. 24, 250 (1956)]. Previously, various workers have uniformly neglected the highest singly excited configuration in the configuration interaction on the grounds of its high energy and because its inclusion destroys the simple linear formulas for the state energies of benzene. The effect of inclusion of this configuration on the spectral matching method of determining nearest‐neighbor βpq, γpq, and γpp, employing the 1B2u, 1B1u, 1E1u, and 3B1u states of benzene has been investigated. The major effect was lowering of [11 | 11] to a value near that expected theoretically when correlation effects are considered. The influence of the new parameters on spectral calculations was explored for benzene, cis‐ and trans‐butadiene, naphthalene, and azulene, and the major effect observed was in the energies of excited triplets. It is su...

The structures of molecular topological spaces

The concepts of general topology are employed to derive a mathematical description of the structures of molecules. It is shown that a topological space on a finite set of points induces a unique graph and that as a consequence there is a uniquely determined topological space associated with every alternant molecule. This space is shown to be identical to the quotient space which results from partitioning the region of real space occupied by a molecule into atomic subregions. The molecular topological space is connected if and only if the molecule is connected and the only molecules having equivalent topological spaces are stereoisomers. Nonalternants are topologically distinguished from alternants by the fact that their graphs are not derivable from a topological space as are those of alternants. A set of graph-theoretical techniques for analyzing the combinatorial structure of finite topologies is developed. The cardinality of the molecular topology is found to be a measure of molecular complexity and the cardinalities of the subspace topologies associated with the bonds of the molecule are accurate measures of relative bond strength. Several empirical correlations between physical properties of molecules and topological measures are found.

1,4,7,10-tetraazatetracyclo[5.5.1.04,13.010,13]tridecane: Degenerate rearrangement of its conjugate acid

Abstract The highly symmetrical 1,4,7,10-tetraazatetracyclo[5.5.1.0 4,13 .0 10,13 ]tridecane ( 1 ) has been synthesized by two methods. The proton NMR spectrum of 1 is analyzed. The cyclic tetraaminomethane derivative undergoes a remarkable series of degenerate prototropic and conformational equilibria. The temperature dependence of the proton NMR spectra of 1 and its conjugate acid 3 are interpreted in terms of a large rate enhancement of intramolecular nucleophilic addition to guanidinium ion 3 (ring-chain tautomerism) compared to its acyclic counterpart.

Electron impact induced fragmentation of triquinacene and related compounds—genesis and structure of C9H7+ ions in the gas phase

Abstract Triquinacene, a (CH)10 hydrocarbon, gives an intense C9H7+ peak upon electron impact. The genesis and nature of this ion were investigated by collision-induced dissociation mass spectrometry and unimolecular dissociation of metastable ions. The results demonstrate that the C9H7+ ion arises directly from the parent C10H10+ ion without prior loss of hydrogen but possesses a structure or a composition of structures essentially identical with those derived from other (CH)10 hydrocarbons and related precursors.

Advances in phototackification

A direct single-layer negative-working phototackification system with application to 4-color half-tone proofing has been invented. It makes use of chemical amplification and is based on photo-induced microphase separation in an initially non-tacky miscible blend of acid-labile and tacky polymers. Factors which influence tack generation are discussed. The system has been sensitized both in the UV for conventional analog proofing and in the near-IR for digital proofing.