An ab initio study of the low-lying electronic states of YO2 and Franck-Condon simulation of the first photodetachment band of YO2(-)

A variety of density functional theory and ab initio methods, including B3LYP, B98, BP86, CASSCF, CASSCF/RS2, CASSCF/MRCI, BD, BD(T), and CCSD(T), with ECP basis sets of up to the quintuple-zeta quality for Y, have been employed to study the X(2)B2 state of YO2 and the X(1)A1 state of YO2(-). Providing that the Y 4s(2)4p(6) outer-core electrons are included in the correlation treatment, the RCCSD(T) method gives the most consistent results and is concluded to be the most reliable and practical computational method for YO2 and YO2(-). In addition, RCCSD(T) potential energy functions (PEFs) of the X(2)B2 state of YO2 and the X(1)A1 state of YO2(-) were computed, employing the ECP28MDF_aug-cc-pwCVTZ and aug-cc-pVTZ basis sets for Y and O, respectively. Franck-Condon factors, which include allowance for Duschinsky rotation and anharmonicity, were calculated using the computed RCCSD(T) PEFs and were used to simulate the first photodetachment band of YO2(-). The simulated spectrum matches very well with the corresponding experimental 355 nm photodetachment spectrum of Wu, H.; Wang, L.-S. J. Phys. Chem. A 1998, 102, 9129, confirming the reliability of the RCCSD(T) PEFs used. Further calculations on low-lying electronic states of YO2 gave T(e)'s and T(vert)'s of the A(2)A1, B(2)B1, and C(2)A2 states of YO2, as well as EAs and VDEs to these states from the X(1)A1 state of YO2(-). On the basis of the ab initio VDEs obtained in the present study, previous assignments of the second and third photodetachment bands of YO2(-) have been revised.     

Rate constants for the reactions of hydroxyl radical with several fluoroethers by the relative rate method

Relative rate experiments were used to measure ratios of chemical kinetics rate constants as a function of temperature for the reactions of OH with eight fluoroethers, including CF3OCF2CHF2, CF3OCF2CHFCF3, CHF2CF2OCHF2, CF3CHFCF2OCH2CF3, (CF3)2CHOCHF2, CF2HCF2OCH2CF3, CHF2CF2OCHFCF3, and CF3CH2OCH2CF3. The temperature ranges were about 270-400 K. Each compound was measured against at least two references. Results are compared with previous data where available. An approach using model compounds for the approximate estimation of rate constants for the fluoroethers is discussed. Observed temperature dependences for fluoroethers from the present work and some literature work are shown to be accurately predictable, based on a previously determined correlation of k298K with the pre-exponential factor, A, in the Arrhenius equation k = Ae(-E/RT).     

Biogenetic hypothesis and first steps towards a biomimetic synthesis of haouamines

A detailed hypothesis for the biogenesis of haouamines is reported herein, supported by experiments headed towards biomimetic synthesis of these compounds.     

Interaction potential and transport properties of NeO(+)

The results of both experimental and theoretical studies of the mobility of O(+) in Ne are reported. Errors in the experiments have been carefully assessed, allowing the obtained data to serve as stringent tests of the ab initio potentials. These potentials were calculated using the RCCSD(T) method, employing basis sets of quintuple-zeta quality. Curves were calculated for the lowest (4)Sigma(-) state [arising from O(+)((4)S) interacting with Ne] and for the (2)Pi state [arising from O(+)((2)D) interacting with Ne]. Then, the effects of spin-orbit coupling were incorporated by using the Breit-Pauli operator. The resulting ground state (Omega=32) of NeO(+) gives mobility values in good agreement with experiment at all field strengths. Values of spectroscopic quantities for the ground electronic state of NeO(+) are also presented.     

Hereditarily finitely based monoids of extensive transformations

It is shown that the monoid E _n of extensive transformations of a chain of order n is hereditarily finitely based if and only if n ≤ 3. It follows that the submonoid OE _n of order-preserving transformations in E _n is also hereditarily finitely based if and only if n ≤ 3.     

Ab initio calculations on SCl2 and low-lying cationic states of SCl2+: Franck-Condon simulation of the UV photoelectron spectrum of SCl2

Geometry optimization calculations were carried out on the (approximate)X (1)A(1) state of SCl(2) and the (approximate)X(2)B(1), (approximate)A(2)B(2), (approximate)B(2)A(1), (approximate)C(2)A(1), (approximate)D(2)A(2), and (approximate)E (2)B(2) states of SCl(2) (+) at the restricted-spin coupled-cluster single-double plus perturbative triple excitation [RCCSD(T)] level with basis sets of up to the augmented correlation-consistent polarized quintuple-zeta [aug-cc-pV(5+d)Z] quality. Effects of core electron correlation, basis set extension to the complete basis set limit, and relativistic contributions on computed minimum-energy geometrical parameters and/or relative electronic energies were also investigated. RCCSD(T) potential energy functions (PEFs) were calculated for the (approximate)X (1)A(1) state of SCl(2) and the low-lying states of SCl(2)(+) listed above employing the aug-cc-pV(5+d)Z basis set. Anharmonic vibrational wave functions of these neutral and cationic states of SCl(2), and Franck-Condon (FC) factors of the lowest four one-electron allowed neutral photoionizations were computed employing the RCCSD(T)aug-cc-pV(5+d)Z PEFs. Calculated FC factors with allowance for the Duschinsky rotation and anharmonicity were used to simulate the first four photoelectron (PE) bands of SCl(2). The agreement between simulated and observed He I PE spectra reported by Colton et al. [J. Electron Spectrosc. Relat. Phenom. 3, 345 (1974)] and Solouki et al. [Chem. Phys. Lett. 26, 20 (1974)] is excellent. However, our FC spectral simulations indicate that the first observed vibrational component in the first PE band of SCl(2) is a "hot" band arising from the SCl(2)(+)(approximate)X(2)B(1)(0,0,0)<--SCl(2)(approximate)X (1)A(1)(1,0,0) ionization. Consequently, the experimental adiabatic ionization energy of SCl(2) is revised to 9.55+/-0.01 eV, in excellent agreement with results obtained from state-of-the-art ab initio calculations in this work.     

Discrete element modelling of the quasi-static uniaxial compression of individual infant formula agglomerates

Infant formula is usually produced in an agglomerated powder form. These agglomerates are subjected to many transient forces following their manufacture. These can be difficult to quantify experimentally because of their small magnitudes and short durations. Numerical models have the potential to address this gap in the experimental data. The objective of the research described here was to calibrate a discrete element model for these agglomerates using experimental data obtained for quasi-static loading, and to use this model to study the mechanics of the particle response in detail. The Taguchi method was previously proposed as a viable calibration approach for discrete element models. In this work, the method was assessed for calibration of the model parameters (e.g., bond stiffnesses and strengths) considering three responses: the force at failure, strain at failure and agglomerate stiffness. The Weibull moduli for the simulation results and the experimental data were almost identical following calibration and the 37% characteristic stresses were similar. An analysis of the energy terms in the model provided useful insight into the model response. The bond energy and the normal force exerted on the platens were strongly correlated, and bond breakage events coincided with the highest energy dissipation rates.     

Enantioselective synthesis of levomilnacipran

A novel approach for the asymmetric synthesis of the active (1S,2R)-enantiomer of the antidepressant milnacipran is reported. The two stereogenic centers borne by the cyclopropane ring were sequentially installed starting from phenylacetic acid.     

Synthesis and reactivity of pelletierine-derived building blocks and pelletierine analogs

Lycopodium alkaloids are unique (and often impressive in terms of structures) polycyclic alkaloids that attract great interest from a biological point of view and that also provide ideal targets for total synthesis. Propylpiperidine units closely related to pelletierine are involved in the biosynthesis of these alkaloids. Therefore, stable pelletierine-like compounds, especially a (R)-phenylglycinol-based oxazolopiperidine analog, were prepared and their reactivity investigated. The compounds described in this work expand the tool-box of small building blocks in the piperidine series and pelletierine analogs and could be suitable for the synthesis of Lycopodium alkaloids following biosynthetically inspired strategies.