Etude des fragmentations en spectrographie de masse de dithiannes-1,3 substitués en 2 par des groupements insaturés

The mass spectra of the title compounds always show an intense molecular ion. Some fissions involve loss of the ethylenic group, while others are related to cleavage of the dithiane ring, eventually followed by recyclizations involving the ethylenic chain stabilized by the resonance possibilities. If a phenyl group is present in the ethylenic chain, the spectra are modified by the formation of the very stable benzothiopyrylium ion.     

Etude en RMN du carbone 13 de dicoumarols substitués

The ¹³C n.m.r. spectrum of the bridge substituted dicoumarols are interpreted in order to obtain structural information for quantitative structure-activity relationships. The results are in agreement with those obtained by ¹H n.m.r. These dicoumarols exhibit double restricted rotation around both bridge bonds.     

Ion-trap mass spectrometry applications in forensic sciences. I. Identification of morphine and cocaine in hair extracts of drug addicts.

Daughter-ion spectra obtained by ion-trap mass spectrometry have been successfully employed in the field of drug abuse investigation. Selection and collision-induced fragmentation of molecular-ion species of morphine and cocaine lead to an easy identification of such molecules in hair extracts of heroin and cocaine addicts.     

Miscibility of polyester/nitrocellulose blends: A DSC and FTIR study

The miscibility of polyester/nitrocellulose blends was investigated by differential scanning calorimetry and Fourier-transform infrared (FTIR) spectroscopy. Two nitrocelluloses (NC) derived from wood and having different nitrogen contents (12.62 and 13.42%) were used. On the basis of the glass transition temperature criterion, poly(?-caprolactone) (PCL), poly(valerolactone), poly(ethylene adipate), and poly(butylene adipate) are miscible with nitrocellulose, whereas poly(α-methyl α-propyl β-propiolactone) and poly(α-methyl β-proiolactone) are immiscible. The T_g versus composition curves of PCL/NC blends do not follow a monotone function but exhibit a singular point at a critical PCL volume fraction of 0.51 for NC-1342 and 0.45 for NC-1262 in agreement with Kovacs' theory. A shift of 17 cm^-1 of the carbonyl stretching band was observed with PCL/NC blends and is taken as evidence for hydrogen bonding interaction between the PCL carbonyl group and NC hydroxyl group. The frequency difference between the free hydroxyl absorbance and the absorbances of the hydrogen-bonded species was found to be 85 cm^-1 in pure NC and 125 cm^-1 in PCL/NC blends; it indicates that the average strength of this interaction is stronger than the corresponding self-associated hydrogen bonding in pure NC. The presence of a dipole-dipole interaction between the nitrate-ester groups of NC and the carbonyl groups of the polyesters is reported. The relative strength of the hydrogen bonding and dipole-dipole interactions is discussed and correlated with polymer miscibility.     

Apurinic DNA reactivity: Modelisation of apurinic DNA breakage with phenylhydrazine and formation of a pyrazole adduct

We have elucidated the exact mechanism of apurinic oligodeoxynucleotide d(Tp[AP]pT) cleavage by phenylhydrazine and shown that the final isolated product is in fact a 3-substituted derivative of 1-phenyl-pyrazole.     

Line tension action on 2D networks of gold nanoparticles obtained by the Bubble Deposition Method

The self-assembling properties of surfactant black films are used to obtain sizeable, dense islands of nanoparticles. Using the "Bubble Deposition Method" (BDM) these films are transferred onto solid substrates. The organisation within the islands evolves when the films are allowed to equilibrate before deposition. The results on model gold particles are discussed in terms of line tension.     

Interstack Interactions in Potassium Bis(1,2-Cyclobutenedione 3,4-dithiolato) Palladate. Crystal Structure

Abstract

Potassium bis(1,2-cyclobutenedione 3,4-dithiolato) palladate (Pd(dithiosquarato)₂K₂) crystallizes in the monolinic system, space group P2₁/c, a = 8.046(2), b = 15.235(4), c = 6.289(1). The dithiosquarate entities are stacked in parallel columns separated by potassium cations and water molecules. π-interactions within a stack are evidenced by the short stacking distance (3.51 Å). Further interstack interactions involve close S…O or O…O interstack contacts. (～3.5 Å). As a result, the structural arrangement is nearly two-dimensional. Conductivity measurements carried out on pressed pellets show a semi-conductive behavior (σ = 2 × 10^?5 Ω^?1 cm¹).     

Coherent thermal radiation

The radiation emitted by a heated body is generally quoted as a typical example of incoherent radiation, in distinction to laser radiation. One is nearly isotropic, the other highly directional; one is spectrally broad, the other quasi-monochromatic. It may come as a surprise that the thermal radiation of a large number of substances is coherent, both in space and time, when it is observed at a distance from the body that is shorter than the wavelength. This behaviour can be understood within an electromagnetic approach to thermal emission. Several recent experiments have confirmed these unexpected properties.     

Synthesis,Electrochemical, and Optical Properties of New Fluorescent,Substituted Thieno[3,2-b][1]Benzothiophenes

The synthesis, electrochemical and optical properties of three fluorescent substituted thieno[3,2-b][1]benzothiophenes (TBT) derivatives, including 3-methoxythieno[3,2-b][1]benzothiophene (3-MeO-TBT), 2,3-dimethylthieno[3,2-b][1]benzothiophene (2,3-diMe-TBT), and 6-methoxythieno[3,2-b][1]benzothiophene-2-carboxylate (6-MeO-TBT-2-COOMe), were investigated. The oxidation potential values varied between 1.40 and 1.20 V/SCE according to the electronic substituent effect, and electropolymerization attempts, performed in 0.1 M LiClO₄ acetonitrile solution, led to the formation of very thin films of poly(3-MeO-TBT) and poly(2,3-di-Me-TBT). Electronic absorption spectra, fluorescence excitation and emission spectra, fluorescence quantum yields (Φ_F) , lifetimes (τ_F), and other photophysical parameters of the three new TBT derivatives were measured in DMSO solutions at room temperature. For the methyl-and methoxy-substituted TBT derivatives, the fluorescence emission peak were slightly red shifted relative to that of unsubstituted TBT (Δλ_em = 1–12 nm) whereas, in the case of 6-MeO-TBT-2-COOMe, a rather strong red-shift (Δλ_em = 73 nm) was attributed to the existence of a “push-pull” electronic interaction of the MeO and COOMe groups. All Φ_F values were rather high, varying between 0.11 and 0.35, according to the substituent effect. Fluorescence decays were mono-exponential and τ_F values were very short, ranging between 0.11 and 0.30 ns for the substituted TBT derivatives until study.