Kinetic and thermodynamic stability of naphthalene oxide and related compounds. A comparative microcalorimetric and computational (DFT) study

The kinetics of the acid-catalyzed ring opening of naphthalene 1,2-oxide (5) in highly aqueous media to give naphthols has been measured by heat-flow microcalorimetry. The reaction enthalpy of this aromatization reaction was measured as DeltaH = -51.3 +/- 1.7 kcal mol(-)(1). The unexpectedly low reactivity of naphthalene oxide is suggested to be due to an unusually large thermodynamic stability. A crude estimate of the stabilization effect, approximately 1 kcal mol(-)(1)(not a significant stabilization), is obtained by using the measured reaction enthalpies of structurally related substrates as references. A larger value (2.7 kcal mol(-)(1)) was obtained by calculation using the B3LYP hybrid functional corrected with solvation energies derived from semiempirical AM1/SM2 calculations. The origin of this effect is discussed in terms of homoconjugative stabilization and homoaromaticity. There is a good linear correlation (with slope = 0.63) between the experimentally measured free energy of activation and the calculated enthalpy of carbocation formation in water.     

A trace theorem for the Dirichlet form on the Sierpinski gasket

In connection with the theory for Brownian motion on fractals, a corresponding Dirichlet form has been defined. We consider here the fractal known as the Sierpinski gasket, and characterize the trace of the domain of the Dirichlet form to the boundary of the gasket, boundary in this context meaning the triangle which confines the gasket.     

New Microphase‐Separated Diblock Copolymers Carrying Semifluorinated Side Groups Prepared by ROMP

We prepared new varied diblock copolymers by ring‐opening metathesis polymerization of functionalized norbornenes and cyclooctene in the presence of Schrock‐type initiators, either [Mo(CHCMe₂Ph)(N‐2,6‐iPr₂Ph)(OCCH₃(CF₃)₂)₂] or [Mo(CHCMe₂Ph)(N‐2,6‐iPr₂Ph)(OC(CH₃)₃)₂]. The block copolymers were microphase separated and presented the individual phases of each polymer block constituent, that were amorphous/amorphous, amorphous/semicrystalline, or semicrystalline/liquid‐crystalline. One example of such a block copolymer is shown.

     

Molecular two-centre integrals between 2 pπ and 3 pπ atomic orbitals

The evaluation of two-centre Coulomb-penetration and exchange-penetration integrals is discussed. All possible penetration integrals between 2pπ and 3pπ atomic orbitals exponent α are reduced analytically and tabulated for α = 1·00 (0·25) 10·00.