Theory of cyclic voltammetry at the mercury film electrode: Reversible case with substrate initially present in the mercury phase

The theory of cyclic voltammetry has been developed for a case describing the behaviour of a reversible system at the mercury film electrode with a metal present initially in the mercury phase. Theoretical results are presented in the form of a simple equation coupled with a set of the calculated current function values. In addition, several simple relationships are given for the parameters characterizing the cyclic curves. The rapid exhaustion of the metal from the mercury film and the generation of the metal ions into the solution free of metal ions offer better conditions for the resolution of adjacent peaks than those existing in cyclic voltammetry at the HMDE and at the MFE with substrate present initially in solution. Theoretical predictions were compared with experimental results obtained for lead and thallium at the silver-based mercury film electrode.     

Absolute configuration, predominant conformations, and vibrational circular dichroism spectra of enantiomers of n-butyl tert-butyl sulfoxide

Alkylation of the alpha-carbanion of (R)-(-)-tert-butyl methyl sulfoxide (4) with n-propyl bromide afforded (+)-n-butyl tert-butyl sulfoxide (1) to which the absolute configuration (R) was ascribed. This assignment was confirmed by X-ray analysis of the complex 6 obtained from the enantiomerically pure sulfoxide (-)-1 and mercury chloride. Vibrational absorption and circular dichroism spectra of (+)-1 were measured in CDCl3 solution in the 2000-900 cm(-1) region and compared with the ab initio predictions of absorption and VCD spectra obtained with density functional theory using the B3LYP/6-31G basis set for different conformers of (R)-1. This comparison indicated also that (+)-1 is of the (R)-configuration.     

Spectrophotometric determination of titanium (IV) with chlorpromazine hydrochloride

Spectrophotometric Determination of Titanium(IV) with Chlorpromazine HydrochlorideThe extraction of titanium(IV)-thiocyanate complex from hydrochloric acid with chlorpromazine (CPA) dissolved in chloroform has been studied. The composition of the extracted species was found to be (CPAH⁺)₂[Ti(CNS)₆²⁻]. This complex, dissolved in chloroform, has maximum absorbance at 417 nm and a molar absorptivity of 2.6 × 10⁴ mol⁻¹ · cm⁻¹ · liter. Titanium(IV) was determined spectrophotometrically in the organic phase. Beer's law is obeyed in the titanium concentration range 0.2-2.2 μg/ml.     

Three-loop mixing of dipole operators

We calculate the complete three-loop O(alpha(3)(s)) anomalous dimension matrix for the dimension-five dipole operators that arise in the standard model after integrating out the top quark and the heavy electroweak bosons. Our computation completes the three-loop anomalous dimension matrix of operators that govern low-energy |DeltaF| = 1 flavor-changing processes, and represents an important ingredient of the next-to-next-to-leading order QCD analysis of the B--> X(s)gamma decay.     

A general synthesis of optically active phosphines,phosphinites and thiophosphinites from alkylthio(alkylseleno)phosphonium salts and tris(dimethylamino)phosphine as a thiophilic agent

Tris(dimethylamino)phosphine was found to be a suitable thiophilic reagent which converts optically active alkylthio(alkylseleno)phosphonium salts into chiral tertiary phosphines and phosphinites with a high stereoselectivity. The first synthesis of optically active thiophosphinites from bis(alkylthio)phosphonium salts and tris(dimethylamino)phosphine is also reported.     

Skew and kurtosis of low-energy heavy-ion distributions implanted in silicon and aluminium

The skew and kurtosis of 10–45 keV heavy-ion distributions in aluminium and silicon have been measured using the radiotracer and peeling technique, and compared with values calculated by the moments method of Winterbon. For Si the agreement is considered to be satisfactory; the disagreement in Al case can be explained as being due to diffusion effects.     

“Clickable” Vitamin B12 Derivative

A “clickable” vitamin B₁₂ derivative possessing the azide functionality at the 5′‐position was synthesized by means of a two‐step procedure on the gram scale. The reaction of cobalamin with mesyl chloride (MsCl) afforded the 5′‐OMs derivative, which was subsequently transformed to the desired 5′‐azide, the structure of which was confirmed using X‐ray analysis. It proved to be reactive in the azide–alkyne 1,3‐dipolar cycloaddition reaction to give substituted triazoles in high yields. A study of the reaction conditions and the scope of the process are reported.     

Solid State Conformation of and the Anomeric Effect in Conformationally Labile and Rigid 2-Thiophosphoryl and 2-Selenophosphoryl Substituted 1,3-Ditianes

Abstract

Conformation and geometry of 2-uophosphoryl and 2-selenophosphoryl 1,3-ditianes is determined by several stereoelectronic and steric efects [1]. The crystal and molecularstrustures of the six compouds shown below have been determined by X-ray methods. The differences in the coresponding bond distances and selected structural parameters for all these compounds are discussed in the context of anomeric effect.     

Phosphonate-Mediated Synthesis of Biologically Active Cyclopentanones and Cyclopentenones

The synthesis and reactivity of 3-(phosphorylmethyl)cyclopent-2-enones as well as a complete desymmetrization of meso -tartaric acid are discussed as a platform for developing the synthesis of racemic rosaprostol and enantiomeric forms of prostaglandin B 1 methyl ester, isoterrein, and neplanocin A.