Photochemistry of bridged cycloheptadienones : Di-π-methane photorearrangement of 6,7-benzobicyclo[3.2.1]octadienone and related dienes

A series of 6,7-Benzobicyclo[3.2.1]octadienes (10–13) have been prepared. Direct and sensitized irradiation of the dienes gave di-π-methane rearrangement products (14–17). Quantum yields for the direct and sensitized rearrangements were recorded and compared. Substituent effect and structure-multiplicity relationships are discussed.     

Kinetics and thermochemistry of the methyl radical: Study of the CH3 + HCl reaction

The kinetics of the reaction between CH₃ and HCl was studied in a tubular reactor coupled to a photoionization mass spectrometer. Rate constants were measured as a function of temperature (296–495 K) and were fitted to an Arrhenius expression: k₁ = 5.0(±0.7) × 10^?13 exp{?1.4(±0.3) kcal mol^?1/RT} cm³ molecule^?1 s^?1. This information was combined with known kinetic parameters of the reverse reaction to obtain Second Law determinations of the methyl radical heat of formation {34.7(±0.6) kcal mol^?1} and entropy {46(±2) cal mol^?1 K^?1} at 298 K. Using the known entropy of CH₃, a more accurate Third Law determination of the CH₃ heat of formation at this temperature was also obtained {34.8(±0.3) kcal mol^?1}. The values of k₁ obtained in this study are between those reported in prior investigations. The results were also used to test the accuracy of the thermochemical information which can be obtained from kinetic studies of R + HX (X = Cl, Br, I) reactions of the type described here.     

General formulation of the first-order perturbation graph theory

A generalization of the perturbation graph theory of Herndon and Párkányi is developed, enabling the calculation of resonance energies of conjugated heterocyclic and inorganic systems possessing any number of π-electrons.     

Ω-Invariance in control systems with bounded controls

The concepts of weakly Ω-invariant sets and strictly weakly Ω-invariant sets in control systems with bounded controls are defined and analyzed. Computable conditions for weak Ω-invariance are derived, and the question of existence of rest points and stationary points in weakly Ω-invariant sets is considered. For linear dynamics, properties of weakly Ω-invariant sets are studied, and questions of constrained reachability are investigated.     

Ethers of indoxylie acid

O-alkylations of indoxylie acid (2b) to produce 3-indolyl-alkyl ethers and a synthesis of 5-melhoxy-2-earboxyindol-3-oxyaeetic acid (25) are described.     

Direct identification of reactive routes and measurement of rate constants in the reactions of oxygen atoms with methanethiol,ethanethiol, and methylsulfide

The room temperature reactions between oxygen atoms and methanethiol, ethanethiol, and methylsulfide have been studied in crossed jets to directly detect and identify the free-radical and stable products they produce. Knowledge of the products was used to assign reactive routes. The overall rate constants for all three O-atom reactions were also measured at 300 ± 2°K using a fast-flow reactor. They are 1.9 (CH₃SH), 2.8 (C₂H₅SH), and 63 (CH₃SCH₃) × 10^?12cm³/mol · sec. The identity of the detected products and the trend in rate constants in these reactions support an electrophilic addition mechanism followed by decomposition of the excited adduct by S-R bond cleavage (R = H, CH₃, or C₂H₅).     

The use of jacobi's lemma in unimodularity theory

The paper applies Jacobi's fundamental result on minors of the adjoint matrix to obtain properties on determinants of unimodular matrices.