Ab Initio molecular orbital calculations

Linear combinations of Gaussian orbitals were contracted to minimal basis sets. The binding energies (B.E.) obtained for the three compounds furan, pyrrole and 1,2,5-oxadiazole are 0.75, 0.84 and 0.26 a.u. respectively. Correlation of these figures and those obtained in related calculations leads to the relationship (B.E.)_exp.=0.7347 (B.E.)_calc.+633 (Kcal/mole). The photoelectron spectra of these compounds are extended and correlated with the orbital energies; the -electron excitations are given by (I.P.)_exp.=1.00 (I.P.)_calc.–2.20 eV. Mulliken population analyses give dipole moments in reasonable agreement with experiment.

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Zusammenfassung Linearkombinationen von Gauß-Orbitalen wurden zu minimalen Basissätzen kontrahiert.Die Bindungsenergien (B.E.) für die drei Komponenten Furan, Pyrrol und 1,2,5-Oxadiazol haben die Werte: 0,75, 0,84 und 0,26 a.u. Setzt man diese Werte zu den berechneten in Beziehung, so erhält man die Gleichung: (B.E.)_exp.=0,7347 (B.E.)_calc.+633 (Kcal/Mol).Die Photoelektronenspektren dieser drei Komponenten werden erweitert und mit den Orbitalenergien korreliert; die -Elektronen-Anregungsenergien werden durch die Beziehung: (I.P.)_exp. =1.00 (I.P.)_calc.–2,20 eV gegeben. Mulliken-Populations-Analysen ergeben die Dipolmomente in bemerkenswerter Übereinstimmung mit experimentellen Werten.

     

Evaluated and estimated kinetic data for phase reactions of the hydroperoxyl radical

Methods are discussed for the production and detection of the hydroperoxyl radical for use in gas phase kinetic studies. Rate constants for gas phase reactions of the hydroperoxyl radical with itself, H₂, H₂O, CO, NO, SO₂, O₃, C₂H₆, C₃H₈, i-and n-C₄H₁₀, C₂H₄, i-C₄H₈, HCHO, C₂H₅CHO, n-C₃H₇CHO, Br, O, OH, and H are critically evaluated. Recommended or estimated rate constant expressions with associated error limits are given applicable over specified temperature ranges (normally 300–1000°K). The reactivity of HO₂ compared with OH, O, H, F, Cl, Br, CH₃, and CH₃O is presented in tabular form and the implications for atmospheric chemistry are discussed.     

Evidence of a rise in the antiproton-proton total cross section at the CERN intersecting storage rings

We measured the total cross section for $\text{p}$p scattering at $\text{s}\text{= 52.8}\text{GeV}$ at the CERN ISR, using the direct, total-rate method. The result obtained, $\text{σ}{}_{\mathrm{<mtext>tot</mtext>}}\text{(}\text{p}\text{p}\text{) = 44.70 ± 0.53}\text{mb}$, shows that, in common with σ_tot(pp), this cross section also starts to rise in the ISR energy range. We remeasured the total cross section for pp scattering at the same energy, obtaining σ_tot(pp) = 43.26 ± 0.33 mb, and found for the difference, $\text{Δσ}{}_{\mathrm{<mtext>tot</mtext>}}\text{= σ}{}_{\mathrm{<mtext>tot</mtext>}}\text{(}\text{p}\text{p}\text{) ? σ}{}_{\mathrm{<mtext>tot</mtext>}}\text{(}\text{pp}\text{)}$, a value of 1.44±0.45 mb.     

Synthesis of 5,6-dimethoxyquinazolin-2(1H)-ones

Synthesis of 5,6-dimethoxyquinazolin-2(1H)-one derivatives was the subject of investigations leading to the preparation of title compounds 11, 13, 14 and 26 . Target quinazolines 1 were synthesized in three ways; the route starting from o-vanillin via the intermediacy of 6-amino-2,3-dimethoxyacetophenone ( 19 ) was used for most of the preparative work. The unexpected formation of an acid-labile dimer of 13 was discovered and solid state ¹³C nmr was used for structural assignment. The 5-methoxy substituent in these systems shows anomalous spectral characteristics and, in one case, was cleaved in acid media to 22 .