The fast peroxyoxalate-chemiluminescence of 3-1-aza-4,10-dithia-7-oxacyclododecane as a novel fluorophore

Due to their multiple selectivities, high sensitivity, and instrumental simplicity peroxyoxalate chemiluminescence (PO-CL) reactions have been used as powerful detection systems in several separation techniques. However many of the PO-CL reactions have slow kinetics and impose extra flow elements in separation systems to obtain acceptable band resolution, overcome the peak broadening and observe the reaction in a reasonable time window at maximum emission intensity. Therefore slow chemiluminescence reactions cannot be used in constructing miniaturized separation systems. To achieve the fast and intense PO-CL reactions (suitable for miniaturized separation systems) careful selection of the fluorophore molecule and the reaction conditions is of great importance. In this work, the time-dependent light emission of the fast chemiluminescence (CL) arising from the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with H₂O₂ in the presence of 3-1-aza-4,10-dithia-7-oxacyclododecane (L) as a novel fluorophore, and imidazole as catalyst, has been studied in ethyl acetate solution. To find the best time-intensity emission curves the concentration of TCPO, imidazole, hydrogen peroxide and L were optimized. The maximum CL intensity and minimum reaction time were obtained at the concentration of 0.2 M H₂O₂, 2.0×10^?3 M TCPO, 1.0×10^?3 M fluorophore and 5.0×10^?3 imidazole. Under the optimum experimental condition, the entire CL reaction is completed in less than 3 s.     

High-resolution infrared and ab initio investigation of CHD2 79Br: Ro-vibrational analysis of the ν6 fundamental and the 2ν6−ν6 hot band

The high-resolution infrared spectrum of CHD₂ ⁷⁹Br has been investigated by Fourier transform spectroscopy in the range 540–615?cm^?1 at an unapodised resolution of 0.0035?cm^?1. This spectral region is characterised by the ν₆ fundamental (584.8510?cm^?1), corresponding to C–Br stretching mode, and its hot band 2ν₆?ν₆ (578.4333?cm^?1). The spectral analysis resulted in the identification of 3430 transitions (J’?≤?73 and K'_a ?≤?18) for the ν₆ fundamental and 1212 transitions (J’?≤?49 and K'_a ?≤?11) for the hot band 2ν₆?ν₆. The assigned data have been fitted using the Watson’s S-reduced Hamiltonian in the I^r representation and new constants for the ground state from about 24,600 combination differences and sets of parameters for the v ₆?=?1 and 2 vibrational states have been obtained. From spectral simulations the intensity ratio between 2ν₆?ν₆ and ν₆ has been estimated to be 0.15?±?0.02. High-quality ab initio calculations have also been performed at the CCSD(T) level of theory in order to support the experimental investigation through the calculation of molecular parameters relevant to ro-vibrational spectroscopy.     

Square-integrability modulo a subgroup

We prove a weak form of the Frobenius reciprocity theorem for locally compact groups. As a consequence, we propose a definition of square-integrable representation modulo a subgroup that clarifies the relations between coherent states, wavelet transforms and covariant localisation observables. A self-contained proof of the imprimitivity theorem for covariant positive operator-valued measures is given.

     

The nucleolus is well-posed

The lexicographic order is not representable by a real-valued function, contrary to many other orders or preorders. So, standard tools and results for well-posed minimum problems cannot be used. We prove that under suitable hypotheses it is however possible to guarantee the well-posedness of a lexicographic minimum over a compact or convex set. This result allows us to prove that some game theoretical solution concepts, based on lexicographic order are well-posed: in particular, this is true for the nucleolus.     

Linear spaces on v points with v−2 mutually intersecting long lines

Finite linear spaces on v points with v–2 mutually intersecting long lines are completely characterized.Dedicated to Professor Giuseppe Tallini on the occasion of his 60^th birthday.Work supported by Italian M.P.I. 8nd by GNSAGA of CNR     

New synthesis of optically active 5-isoxazolidinones and beta-amino acids

A new simple and stereoselective synthesis of 5-isoxazolidinones based on the reaction of lithiated 2-isopropyl-2-oxazolines with nitrones is described. A chiral version of such a methodology allows the preparation of highly enantioenriched 5-isoxazolidinones which are useful precursors for the synthesis of beta-amino acids     

Oxazolinyloxiranyllithium-mediated stereoselective synthesis of alpha-epoxy-beta-amino acids

[reaction: see text] The stereoselective synthesis of novel alpha-epoxy-beta-amino acids is described by a route that combines the chemistry of oxazolinyloxiranyllithiums with that of nitrones. The intermediate trioxadiazadispiro[2.0.4.3]undecanes 4 have been isolated and converted by hydrolysis into epoxy-5-isoxazolidinones 5 which can be transformed into the alpha-epoxy-beta-amino acids 8 by N-O reduction.     

An efficient route to tetrahydronaphthols via addition of ortho-lithiated stilbene oxides to alpha,beta-unsaturated fischer carbene Complexes

[reaction: see text] A stereoselective/stereospecific synthesis of polysubstituted tetrahydronaphthols based on the Michael addition of ortho-lithiated stilbene oxides to alpha,beta-unsaturated Fischer carbene complexes followed by an unusual cyclization of the corresponding intermediate in a 6-endo-tet mode is described.