Kinetic determination of organic vapor mixtures with single piezoelectric quartz crystal sensor using artificial neural networks

A single piezoelectric quartz crystal coated with one kind of crown ether was applied to the simultaneous determination of binary acid and amine vapor mixtures. From the adsorption and desorption curves of analytes, which were somewhat different in shape, frequency shifts from ten time windows were taken as inputs for artificial neural networks (ANN). Prediction results were satisfactory for ANN in both sample sets. The average relative errors, for formic acid and acrylic acid were 5%, for n-butylamine and aniline, they were 3% with ANN respectively. The effects of number of neurons in the hidden layer of ANN on the performance of the network are also discussed.     

DIRECT DETERMINATION OF NEODYMIUM AND ERBIUM IN RARE EARTH MIXTURE BY DERIVATIVE SPECTROPHOTOMETRY

The absorption spectra of 4f electron transitions of the complexes of neodymium and erbium with 8-hydroxyquinoline-5-sulphonic acid in the presence of diethylamine and ethanol have been measured by normal and third-derivative spectrophotometry. Their molar absorptivities are 70.7 l.mol~(-1).cm~(-1) for Nd and 62.5 l.mol~(-1).cm~(-1) for Er. They are 7.6 times and 14.9 times greater than those of corresponding chlorides, respectively. Use of the third-derivative spectra both eliminates the interference of Ce(Ⅳ) and increases the sensitivity for Nd and Er. Beer,s Law was obeyed from 0-10 ug/ml of Nd and Er. The method has been applied to the determination of neodymium and erbium in rare earth mixtures.     

N,N''''-硝基苯酰基取代苯酰氨基硫脲的合成与生物活性

酰氨基硫脲类化合物不仅具有广谱抗菌性能 ,还具有极好的杀虫和植物生长调节活性 [1～ 3] ,因而引起许多国内外学者对硫脲类化合物的合成及其化学结构与生物活性关系方面的研究 [4～ 8] .为了进一步研究不同的取代基团对此类化合物生物活性的影响 ,作者用硝基苯酰基异硫氰酸酯与芳基酰肼加成制得相应的 N ,N -硝基苯酰基取代苯酰氨基硫脲 ( ) ,并初步测定了它们抑制大肠杆菌和枯草杆菌生长的生物活性 .这些化合物尚未见文献报道 .Ar— COCl KSCN Ar—CONCS a～ cAr CONHNH2 ( 1 ～ 7) Ar—CONHC( S) NHNHCOAr Ar:a.o-N…     

多缩乙二醇二苯醚与甲醛缩聚合成酚醛型聚合物假冠醚的研究

本文采用苯酚、多缩乙二醇二氯化物、多缩乙二醇等为起始原料,合成了九个多缩乙二醇二苯醚新单体,经甲醛聚合获得一系列聚合物假冠醚,并对它们的溶解性能、络合性能以及催化作用等进行研究。     

Manganese/Bicarbonate-catalyzed epoxidation of lipophilic alkenes with hydrogen peroxide in ionic liquids

[reaction: see text] Effective epoxidation of lipophilic alkenes using hydrogen peroxide was accomplished with the manganese sulfate/bicarbonate catalytic system in an ionic liquid at room temperature.     

Rate constants for the reactions of a series of alkylperoxy radicals with NO

The rate constants for the gas-phase reactions of isopropyl- and tert-butylperoxy radicals with nitric oxide (NO) have been studied at 298 +/- 2 K and a total pressure of 3-4 Torr (He buffer) using a laser flash photolysis technique coupled with a time-resolved negative-ionization mass spectrometry. The alkyl peroxy radicals were generated by the reaction of alkyl radicals with excess O(2), where alkyl radicals were prepared by laser photolysis of several precursor molecules. The rate constants were determined to be k(i-C(3)H(7)O(2) + NO) = (8.0 +/- 1.5) x 10(-12) and k(t-C(4)H(9)O(2) + NO) = (8.6 +/- 1.4) x 10(-12) cm(3) molecule(-1) s(-1). The results in combination with our previous studies are discussed in terms of the systematic reactivity of alkyl peroxy radicals toward NO.     

Ru2(ap)4(sigma-oligo(phenyleneethynyl)) molecular wires: synthesis and electronic characterization

Reported in this contribution are the synthesis, characterization, and charge transport properties of wire-like Ru2(ap)4(OPEn), where ap is 2-anilinopyridinate and OPE is -(CCC6H4)nSCH2CH2SiMe3 with n = 1 (1) and 2 (2). Scanning tunneling microscopy (STM) measurements of compound 2 inserted into a SAM of C11 thiol reveal that molecule 2 exhibits (i) the stochastic switching characteristic of wire molecules embedded in insulating SAMs and (ii) higher conductivity than the C11 thiol SAM. More importantly, analysis of the molecular electronic decay constant (beta) exhibits a decrease of at least 15% as compared to purely organic molecular analogues. Hence, the transport characteristics of molecules can be significantly improved for nanoscale electronics through the incorporation of a Ru2 fragment into conjugated backbone.     

Characterization of C8H10 alkylbenzenes by negative ion mass spectrometry

The O^?˙ chemical ionization mass spectrri of the C₈H₁₀ alkylbenzenes, o-, m-. andp -xylene and ethylbenzene, show formation of [M ? H + O]^?, [M ? H]^?, [M ? H₂]^?˙ and, for the xylenes, [M ? CH₃ + O]^? as primary reaction products; the relative importance of these products depends on the isomer. However, [OH]^? is a primary product from reaction of O^?˙ with both the C₈H₁₀ isomers and hydrogen-containing impurities; [OH]^? reacts further with the alkylbenzenes to produce [M ? H]^? with the result that the chemical ionization mass spectra depend on experimental conditions such as sample size and the presence of impurities. The collision-induced charge inversion mass spectra of the [M ? H + O]^? and [M ? H]^? products allow only distinction of ethylbenzene from the xylenes. However, the collision-induced charge inversion mass spectra of the [M ? H₂]^?˙ ions show differences which allow identification of each isomer.     

Highly Regioselective Sequential 1,1‐Dihydrosilylation of Terminal Aliphatic Alkynes with Primary Silanes

A regioselective double 1,1‐hydrosilylation of terminal aliphatic alkynes with primary silanes catalyzed by one cobalt catalyst has been developed. gem‐Bis(dihydrosilyl)alkanes containing four silicon‐hydrogen bonds are efficiently constructed in an atom‐economical manner. Tolerated substrates include simplest alkyne‐ethyne, a complicated drug derivative and various functionalized terminal aliphatic alkynes. Asymmetric approach using two catalysts is achieved with excellent enantioselectivities to access corresponding chiral products. The transformations of Si—H bonds into Si—C, Si—O, and Si—F bonds and the synthesis of enantioriched α‐hydroxysilane show synthetic utility.     

Streamlined construction of peptide macrocycles via palladium-catalyzed intramolecular S-arylation in solution and on DNA

A highly efficient and versatile method for construction of peptide macrocycles via palladium-catalyzed intramolecular S-arylation of alkyl and aryl thiols with aryl iodides under mild conditions is developed. The method exhibits a broad substrate scope for thiols, aryl iodides and amino acid units. Peptide macrocycles of a wide range of size and composition can be readily assembled in high yield from various easily accessible building blocks. This method has been successfully employed to prepare an 8-million-membered tetrameric cyclic peptide DNA-encoded library (DEL). Preliminary screening of the DEL library against protein p300 identified compounds with single digit micromolar inhibition activity.

A highly efficient and versatile method for construction of peptide macrocycles via palladium-catalyzed intramolecular S-arylation of alkyl and aryl thiols with aryl iodides under mild conditions is developed.