Chelate synthesis of 2,2′-bipyridin-4-one

A method for the synthesis of 2,2′-bipyridin-4-one from 4-amino-4-(2-pyridyl)-but-3-en-2-onevia its diphenylboron, chelates was proposed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2071–2073, November, 1997.     

A priori investigation of subgrid correlation of mixture fraction and progress variable in partially premixed flames

Subgrid correlation of mixture fraction, Z, and progress variable, c, is investigated using direct numerical dimulation (DNS) data of a hydrogen lifted jet flame. Joint subgrid behaviour of these two scalars are obtained using a Gaussian-type filter for a broad range of filter sizes. A joint probability density function (JPDF) constructed using single-snapshot DNS data is compared qualitatively with that computed using two independent β-PDFs and a copula method. Strong negative correlation observed at different streamwise locations in the flame is captured well by the copula method. The subgrid contribution to the Z–c correlation becomes important if the filter is of the size of the laminar flame thickness or larger. A priori assessment for the filtered reaction rate using the flamelet approach with independent β-PDFs and correlated JPDF is then performed. Comparison with the DNS data shows that both models provide reasonably good results for a range of filter sizes. However, the reaction rate computed using copula JPDF is found to have a better agreement with the DNS data for large filter sizes because the subgrid Z–c correlation effect is included.     

Redox-linked protein dynamics of cytochrome c probed by time-resolved surface enhanced infrared absorption spectroscopy

Time-resolved surface enhanced infrared absorption (SEIRA) spectroscopy is employed to analyse the dynamics of the protein structural changes coupled to the electron transfer process of immobilised cytochrome c (Cyt-c). Upon electrostatic binding of Cyt-c to Au electrodes coated with self-assembled monolayers (SAMs) of carboxyl-terminated thiols, cyclic voltammetric measurements demonstrate a reversible redox process with a redox potential that is similar to that of Cyt-c in solution, and a non-exponential distance-dependence of the electron transfer rate as observed previously (D. H. Murgida and P. Hildebrandt, Chem. Soc. Rev. 2008, 37, 937). On the basis of characteristic redox-state-sensitive amide I bands, the protein structural changes triggered by the electron transfer are monitored by rapid scan and step scan SEIRA spectroscopy in combination with the potential jump technique. Whereas the temporal evolution of the conjugate bands at 1693 and 1673 cm(-1) displays the same rate constants as electron transfer, the time-dependent changes of the 1660-cm(-1) band are slower by about a factor of 2. The study demonstrates that time-resolved SEIRA spectroscopy provides further information about the dynamics and mechanism of interfacial processes of redox proteins, thereby complementing the results obtained from other surface-sensitive techniques. In comparison with previous surface enhanced resonance Raman spectroscopic findings, the present results are discussed in terms of the local electric field strengths at the Au/SAM/Cyt-c interface.     

Pauli exchange effects in the elastic scattering of O + O

The real optical potential for ¹⁶O+¹⁶O system is calculated within a generalized version of the double-folding model with the Pauli knock-on exchange effects between the projectile nucleons and the target nucleons taken into account from first principle. The elastic scattering data at E_lab=350 MeV supplemented by the new measurement at larger angles seem to be the first case in heavy-ion scattering where one can test the reliability of different theoretical heavy-ion optical potentials. Predictions are made for the elastic scattering of ¹⁶O+¹⁶O at laboratory energies of 240–480 MeV to illustrare the energy dependence of the rainbow structure which has been clearly observed in experiment at 350 MeV.     

Rearrangements of transient neutral molecules in the gas phase. Does the conversion of CCCHO to HCCCO involve oxygen or hydrogen migration?

Stable (CC13CHO)- may be formed in the chemical ionisation ion source of a VG ZAB 2HF mass spectrometer by the SN2(Si) reaction between Me3SiC[triple bond]C13CHO and F-. Vertical (Franck-Condon) one-electron oxidation of (CC13CHO)- in the first of the tandem collision cells of a VG ZAB 2HF mass spectrometer gives CC13CHO. Some of these neutrals have sufficient excess energy to effect rearrangement to HCC13CO, some of which are energised and to decompose to HCC. and 13CO. Thus the neutral rearrangement exclusively involves H migration: no products from O migration are detected. The corresponding two-electron oxidation of (CC13CHO)- gives mainly unrearranged (CC13CHO)+. A minority of these cations are energised and rearrange by H and O migration to yield (HCC13CHO)+ and (OCC13CHO)+ respectively. All experimental observations are backed up by molecular modelling at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31G(d) level of theory.     

Redox‐Triggered CC Coupling of Diols and Alkynes: Synthesis of β,γ‐Unsaturated α‐Hydroxyketones and Furans by Ruthenium‐Catalyzed Hydrohydroxyalkylation

Direct ruthenium‐catalyzed C? C coupling of alkynes and vicinal diols to form β,γ‐unsaturated ketones occurs with complete levels of regioselectivity and good to complete control over the alkene geometry. Exposure of the reaction products to substoichiometric quantities of p‐toluenesulfonic acid induces cyclodehydration to form tetrasubstituted furans. These alkyne‐diol hydrohydroxyalkylations contribute to a growing body of merged redox‐construction events that bypass the use of premetalated reagents and, hence, stoichiometric quantities of metallic by‐products.