Polyurethane/polystyrene‐silica electrospun nanofibrous composite for the headspace solid‐phase microextraction of chlorophenols coupled with gas chromatography

A novel electrospun composite nanofiber‐based adsorbent (polyurethane/polystyrene‐silica) was fabricated, characterized, and used in the headspace solid‐phase microextraction of the acetylated derivatives of chlorophenols in water samples before gas chromatography with micro electron capture detection. The surface morphology, chemical composition, thermal stability, and structure of the fibers were investigated by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and Brunauer–Emmett–Teller and Barrett–Joyner–Halenda techniques. The effect of the main parameters influencing the efficiency of the method including extraction temperature, salt concentration, and extraction time was investigated and the optimized conditions were obtained. The linear dynamic ranges were 0.1–800 ng/mL. The relative standard deviations (n = 3) and the limits of detection were 2.64–9.57% and 0.0234–0.830 ng/mL, respectively. The relative recoveries for real samples (river water and sewage of our university campus) were between 90.8 and 111%.     

Amplified emission of phthalocyanine isolated in cryogenic matrices

Laser induced fluorescence spectroscopy of free-base (H(2)Pc) and zinc (ZnPc) phthalocyanines trapped in rare gas and nitrogen matrices reveals a quite unexpected phenomenon with a moderate increase in the laser intensity. In all matrices except Xe, a huge increase occurs in the intensity of an emission band near 755 nm when pumping the S(1) <-- S(0) transition. The band involves a vibrational mode of the ground state, located at 1550 and 1525 cm(-1) for H(2)Pc and ZnPc, respectively. Many of the characteristics of amplified emission (AE) are exhibited by this vibronic transition. Excitation scans recorded for the AE band yield greatly enhanced site selectivity compared to what is obtained in normal fluorescence excitation scans.     

Synthesis of new phosphonato esters by reaction between triphenyl or trialkyl phosphite and acetylenic diesters in the presence of NH‐containing compounds

The reaction between triphenyl or trialkyl phosphite and acetylenic esters in the presence of some heterocyclic or aromatic NH compounds such as thiazolidine‐2,4‐dione, 2‐methyl indole, 5‐bromoisatine, 3‐nitroacetanilide, saccharin, 5,5‐dimethylhydantoin, 2‐nitroaniline, 4‐nitroaniline, benzophenon hydrazine, and anthranilic acid led to the formation of phosphonato esters in high yield. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:630–639, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20725     

Synthesis and conformational analysis of 2'-fluoro-5-methyl-4'-thioarabinouridine (4'S-FMAU)

An improved synthesis of 2'-deoxy-2'-fluoro-5-methyl-4'-thioarabinouridine (4'S-FMAU) is described. Participation of the 3'-O-benzoyl protecting group in the thiosugar precursor influenced the stereochemistry of the N-glycosylation reaction in nonpolar solvents, permitting a higher beta/alpha ratio than previously observed for similar Lewis acid catalyzed glycosylations. Conformational analysis of the nucleoside using 3JHH and 3JHF NMR coupling constants together with the PSEUROT program showed that it adopted a predominantly northern conformation in contrast to 2'-deoxy-2'-fluoro-5-methylarabinouridine (FMAU), whose PSEUROT conformational analysis is presented here for the first time, which showed a dominantly southeast conformation. The sharp conformational switch attained by replacing the ring heteroatom is attributed to a decrease in relevant steric and stereoelectronic effects.