Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “NAPHTHALENE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,063 records · Page 59Linked to original sources
PubMed2006

Uptake and UV-photooxidation of gas-phase PAHs on the surface of atmospheric water films. 1. Naphthalene.

The adsorption and photochemical reaction of naphthalene vapor at the air-water interface of water films (22 microm and 450 microm) were studied in a horizontal flow reactor. Experiments were conducted in the regime where gas-phase mass transfer resistance did not limit the uptake. The equilibrium uptake was dependent on water film thickness only below 1 microm. Bulk water-air and air-to-interface partition constants were estimated from the experiments. The equilibrium partition constant between the water film and air decreased with increasing temperature. Photochemical reaction products were isolated in the water film after exposure to UV light. Four main oxygenated products were identified (1,3-indandione, 1(3H)-isobenzofuranone (phthalide), 2H-1-benzopyran-2-one (coumarin), and 1-naphthol). The initial rates of product formation were 46 to 154% larger for the thin film (22 microm) compared to both a thick film (450 microm) and bulk aqueous phase photooxidation. The atmospheric implications of reactions in water films are discussed.

Journal Article↗
PubMed2006

Molecular motion in crystalline naphthalene: analysis of multi-temperature X-ray and neutron diffraction data.

Single crystals of h8-naphthalene have been examined by both X-ray and neutron diffraction over a range of temperatures from 5 to 295 K. The aim of this case study was to measure the anisotropic displacement parameters (ADPs) of carbons and hydrogens and to interpret them using the model of thermal motion proposed by Bürgi and Capelli (Acta Cryst. 2000, A56, 403). The traditional rigid-body analysis expresses the low-frequency motions in terms of molecular translations and librations only, whereas the Bürgi-Capelli treatment also includes the high-frequency internal modes. We show that a considerable improvement occurs by representing the internal modes by a single second-rank tensor and that a further improvement follows by including a Grüneisen parameter to account for volume thermal expansion. By applying the treatment to multi-temperature diffraction data, there is a considerable reduction in the ratio of number of adjustable parameters/number of independent observations.

Journal Article↗
PubMed2006

Photostability via sloped conical intersections: a computational study of the excited states of the naphthalene radical cation.

On the basis of an extensive ab initio electronic structure study of the ground and excited-state potential energy surfaces of the naphthalene radical cation (N*+), we propose a mechanism for its ultrafast nonradiative relaxation from the second excited state (D2) down to the ground state (D0), which could explain the experimentally observed photostability [Zhao, L.; Lian, R.; Shkrob I. A.; Crowell, R. A.; Pommeret, S.; Chronister, E. L.; Liu, A. D.; Trifunac, A. D. J. Phys. Chem. A., 2004, 108, 25]. The proposed photophysical relaxation pathway involves internal conversion from the D2 state down to the D0 state via two consecutive, accessible, sloped conical intersections (CIs). The two crossings, D0/D1 and D1/D2, are characterized at the complete active space self-consistent field (CASSCF) level. At this level of theory, the D0/D1 crossing is energetically readily accessible, while the D1/D2 CI appears too high in energy to be involved in internal conversion. However, the inclusion of dynamic correlation effects, via single point CASPT2 calculations including excitations out of the valence pi- and sigma-orbitals, lowers the D0 and D2 state energies with respect to D1. Extrapolations at the CASPT2 level predict that the D1/D2 crossing is then significantly lower in energy than with CASSCF indicating that with a higher-level treatment of dynamic correlation it may be energetically accessible following vertical excitation to D2. N*+ is proposed as one of the species contributing to a series of diffuse infrared absorption bands originating from interstellar clouds. Understanding the mechanism for photostability in the gas phase, therefore, has important consequences for astrophysics.

Journal Article↗
PubMed2004

Aggregation of sodium 1-(n-alkyl)naphthalene-4-sulfonates in aqueous solution: micellization and microenvironment characteristics.

In aqueous solution, the micellization and microenvironment characteristics of the micelle assemblies of three anionic surfactants, sodium 1-(n-alkyl)naphthalene-4-sulfonates (SANS), have been investigated by steady-state fluorescence and time-resolved fluorescence decay techniques using pyrene, Ru(bpy)3(2+), and 1,6-diphenyl-1,3,5-hexatriene as fluorescence probes. The critical micelle concentrations (cmc's), effective carbon atom numbers (neff's), hydrophilic-lipophilic balances (HLBs), mean micelle aggregation numbers, micropolarities, and microviscosities of these surfactant micelles have been determined. The logarithmic cmc of the alkylnaphthalene sulfonates decreases linearly with an increase in the neff. The logarithmic aggregation number of the alkylnaphthalene sulfonates increases linearly with an increase in the neff. However, in contrast to the alkylsufonates and the alkylbenzene sulfonates, the aggregation for these alkylnaphthalene sulfonate molecules is less sensitive to the increase in the neff. The micropolarity of these alkylnaphthalene sulfonate micelles is less sensitive to the increase in the alkyl chain length and is lower than that of sodium dodecyl sulfate (SDS). The microviscosity of these alkylnaphthalene sulfonate micelles increases with an increase in the alkyl chain length and is lower than those of nonionic surfactants and zwitterionic surfactants. These results suggest that naphthyl rings have a notable effect on the micellization of SANS.

Journal Article↗
PubMed2003

Naphthalenes, isoquinolines, and a benzazocine from zirconocene-copper-mediated coupling of benzocyclobutadiene with nitriles and alkynes.

[reaction: see text] Commercially available 1-bromobenzocyclobutene is a potentially useful synthon particularly with the application of organometallic methodology. Here we show that it is readily converted into Cp(2)Zr(benzocyclobutadiene), which couples with alkynes or nitriles giving five-membered zirconacycles. Treatment of these alkyne- or nitrile-derived zirconacycles with CuCl yields substituted naphthalenes, isoquinolines, or in the presence of MeO(2)C-CC-CO(2)Me, a 3-benzazocine containing an eight-membered ring [corrected].

Journal Article↗
PubMed2000

(8-Naphthalen-1-ylmethyl-4-oxo-1-phenyl-1,3,8-triaza-spiro[4. 5]dec-3-yl)-acetic acid methyl ester (NNC 63-0532) is a novel potent nociceptin receptor agonist.

Spiroxatrine was identified as a moderately potent (K:(i)=118 nM) but non-selective agonist at the human nociceptin/orphanin FQ receptor, ORL1. This compound was subject to chemical modification and one of the resulting compounds, (8-naphthalen-1-ylmethyl-4-oxo-1-phenyl-1,3,8-triaza-s piro[4. 5]dec-3-yl)-acetic acid methyl ester (NNC 63-0532) was shown to have high affinity for ORL1 (K:(i)=7.3 nM). NNC 63-0532 showed only moderate affinity for the following receptors (K:(i) values in parentheses): mu-opioid (140 nM), kappa-opioid (405 nM), dopamine D(2S) (209 nM), dopamine D(3) (133 nM) and dopamine D(4.4) (107 nM) out of 75 different receptors, ion-channels and transporters. In functional assays, NNC 63-0532 was shown to be an agonist at ORL1 (EC(50)=305 nM), a much weaker agonist at the mu-opioid receptor (EC(50)>10 microM) and an antagonist or weak partial agonist at dopamine D(2S) (IC(50)=2830 nM). Thus, NNC 63-0532 is a novel non-peptide agonist with approximately 12 fold selectivity for ORL1 and may be useful for exploring the physiological roles of this receptor owing to its brain-penetrating properties.

Acetates↗
PubMed2003

The radical anions and the electron affinities of perfluorinated benzene, naphthalene and anthracene.

Although benzene and naphthalene do not have electron affinities in the conventional sense, perfluorobenzene and perfluoronaphthalene have nonzero electron affinities. Theoretical methods extensively calibrated with experiment for the prediction of electron affinities (EAs) predict the EAs of perfluorobenzene, perfluoronaphthalene and perfluoroanthracene as 0.69, 1.02 and 1.84 eV, respectively. A rough estimate of 2.39 eV is made for the electron affinity of perfluorotetracene. Thus the perfluoro polycyclic aromatic hydrocarbons (PAHs) are predicted to be effective electron acceptors.

Journal Article↗
PubMed2003

Ester derivatives of hexahomotrioxacalix[3]naphthalenes: conformational and binding properties with alkali metal cations.

The syntheses of the triesters formed between ethyl bromoacetate and hexahomotrioxacalix[3]naphthalene 8, and its tert-butyl analogue 11, are described. Depending on the conditions employed, cone or partial cone conformers are produced. The conformations appear to have some influence on their complexation in neutral medium, with alkali metal cations. The X-ray structure of the partial cone triester 10 is presented.

Journal Article↗
PubMed2003

Naphthalene in the higher triplet excited state.

Naphthalene in the higher triplet excited state Np(Tn) was generated from the two-step excitation method using two-colour two-laser flash photolysis technique and the lifetime of Np(Tn) was estimated to be 4.5 ps from the triplet energy quenching by quenchers such as p-dichlorobenzene, o-dicyanobenzene and carbon tetrachloride.

Journal Article↗