Showing papers by "Yuhong Wang published in 2002"
TL;DR: Gas-phase computational results for the meta- and ortho-substituted PCC species are presented, along with selected linear free energy (LFE) relationships for the para and meta species.
Abstract: The effect of aromatic substitution on the singlet−triplet energy gap in substituted phenyl(carbomethoxy)carbene (X−Ph−C−CO2CH3, PCC) has been explored by time-resolved infrared (TRIR) spectroscopy and gas-phase computational methods. The ground state of para-substituted PCC is calculated to change from the triplet state in p-NO2-PCC (ΔGST = 6.1 kcal/mol) to the singlet state in p-NH2-PCC (ΔGST = −2.8 kcal/mol). The absence of solvent perturbation in the TRIR spectra of p-N(CH3)2-PCC (which should have electronic properties similar to p-NH2-PCC) and parent PCC is consistent with their ground states lying >±2 kcal/mol from the next available electronic state, in line with the computational results. The observation of solvent perturbation in the TRIR spectra of p-OCH3-PCC and p-CH3-PCC implies that their ground states lie <±1 kcal/mol from their next available electronic state. This is in agreement with our computational results, which predict a gas-phase ΔGST of −0.8 and 1.6 kcal/mol for p-OCH3-PCC and p-C...
34 citations
TL;DR: The solvent dependence of the 2-naphthyl(carbomethoxy)carbene (2) singlet-triplet energy gap has been examined and it is suggested that solvent and geometry effects on the entropy of singlet and triplet carbenes can offset differences arising from spin multiplicity.
Abstract: The solvent dependence of the 2-naphthyl(carbomethoxy)carbene (2) singlet−triplet energy gap has been examined by time-resolved infrared (TRIR) and computational methods. The ground state of 2 changes from the triplet state in hexane to the singlet state in acetonitrile. Preferential stabilization of the singlet carbene is the result of its increased dipole moment in polar solvents. Variable-temperature TRIR experiments provide measurements of the enthalpic and entropic differences between 12 and 32 and suggest that solvent and geometry effects on the entropy of singlet and triplet carbenes can offset differences arising from spin multiplicity. B3LYP calculations using the polarizable continuum solvation model (PCM) reproduce the general trends in enthalpic differences seen experimentally.
33 citations
TL;DR: In this paper, the especial function of zeolite to remove N -nitrosamines along with the latest progress in new cigarette containing Zeolite was reported. But no change in the taste of cigarette was observed.
Abstract: This paper reports the especial function of zeolite to remove N -nitrosamines along with the latest progress in new cigarette containing zeolite. N -nitrosamines in cigarette smoke can be strongly adsorbed and catalytic degraded by zeolite additive without any change in the taste of cigarette.
23 citations
DOI•
01 Aug 2002TL;DR: In this article, the authors address issues related to transferring the responsibility for quality control from the Kentucky Transportation Cabinet (KyTC) to construction contractors, with emphasis on quality control/quality assurance administration, QC/QA procedures, quality acceptance and verification testing and CPQC training.
Abstract: This report addresses issues related to transferring the responsibility for quality control from the Kentucky Transportation Cabinet (KyTC) to construction contractors. Surveys of the KyTC, other state departments of transportation, and Kentucky highway contractors were done to identify the advantages, concerns, and modifications of the Contractor Performed Quality Control (CPQC) program. An advisory committee of experienced KyTC engineers, Federal Highway Administration representatives, and contractor representatives met periodically to identify approaches for handling key issues of the program. Several key topics related to CPQC are presented in this report, with emphasis on quality control/quality assurance (QC/QA) administration, QC/QA procedures, quality acceptance and verification testing, and CPQC training. Specific issues related to CPQC pay items in Kentucky are also discussed. Several recommendations have been proposed to enhance the program. If properly implemented, CPQC can improve a contractor's work performance and help relieve the State's burden for inspection. Additional monitoring of the program is necessary to make further improvements and to include other pay items.
6 citations
TL;DR: In this article, the superbasicity of potassium modified ZrO 2 was characterized by Ex-situ IR of chemisorbed carbon dioxide and In-Situ Raman spectra of pyrrole, and several surface carbonates were identified as bicarbonates, monodentates and bidentate species.
Abstract: Superbasicity of potassium modified ZrO 2 can be characterized by Ex-situ IR of chemisorbed carbon dioxide and In-situ Raman spectra of chemisorbed pyrrole. All of the basic sites detected by these methods are lattice oxygen species that are strong electron-pair donor (EPD) Lewis basic site. Several surface carbonates are identified as bicarbonates, monodentates and bidentate species. As an H-bonding donator, moreover, pyrrole interacts with surface basic site to form a strong colinear NH−O through the H-bond between the basic site and the chemical adsorbed pyrrole, resulting in a sharp band at 1136 cm −1 .
2 citations
TL;DR: In this paper, the authors showed that CaO/NaY and NaZSM-5 composites possess an extraordinary high basic strength with H of 27.5 K after activation at 873 K.
Abstract: Calcium oxide could be dispersed on zeolite NaY or NaZSM-5 to form strong basic sites on the host by the use of microwave radiation. After activation at 873 K, some CaO/NaY and CaO/NaZSM-5 composites possess an extraordinary high basic strength with H of 27. Moreover, these strong basic materials had a high water-stability.
1 citations