Investigating Possible Dipole-Bound States of Cyanopolyynes: the Case for the C5N− Anion Detected in Interstellar Space

We present results of quantum structure calculations aimed at demonstrating the possible existence of dipole-bound states (DBS) for the anion , a species already detected in the Interstellar medium (ISM). The positive demonstration of DBS existence using ab initio studies is an important step toward elucidating possible pathways for the formation of the more tightly bound valence bound states (VBS) in environments where free electrons from starlight ionization processes are known to be available to interact with the radical partner of the title molecule. Our current calculations show that such excited DBS states can exist in , in agreement with what we had previously found for the smallercyanopolyyne in the series: the anion. This system has a very weakly bound anion with binding energies of about 3 and 9 cm⁻¹ for the and DBS, respectively.     

Rapid estimation of chemical kinetics by implicit calibration. II

This study continues the development of a method, implicit calibration, for estimating kinetic parameters from on-line measurements of batch reactions. The basic idea of implicit calibration is to combine non-linear parameter estimation with the calibration of measured spectra with concentrations calculated by an assumed kinetic model. A new example is studied, an esterification reaction with a rather complicated kinetic mechanism, where activities, instead of concentrations, and NIR spectra are used as measurements. The emphasis in the study is on estimating the uncertainty of the kinetic parameters. Two approaches, linearization and bootstrap, are applied. In the case studied, the two approaches give closely similar estimates of the uncertainty. As well, a new way is introduced to control the rigidity of the implicit calibration, based on minimizing the lack of fit of the model. It is also shown that ‘mixed implicit calibration’, i.e. implicit calibration combined with a few off-line calibrated concentrations, greatly enhances the identifiability of the kinetic model. Copyright © 2003 John Wiley & Sons, Ltd.     

Plus-Size DiPAMP Hybrids for Advanced Rhodium(I)-Catalyzed Hydrogenation: The 2RBigFUS Model

Outfitting the P,P′-distereogenic 2MeBigFUS ligand with the characteristic branched/functionalized-alkoxy feature of the R-SMS-Phos design furnished the 2RBigFUS family (Figure 2). Rhodium(I) complexes thereof exhibited a further boosted activity and superior enantioselectivity in the hydrogenation of various functionalized olefins, including the challenging α-arylacrylic acids. The application under practical conditions to enantiomeric active pharmaceutical ingredients (APIs) and relevant synthetic building blocks capped the outcome.