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Substituted Phenols (substituted + phenol)
Selected AbstractsUltraviolet Absorption Spectra of Substituted Phenols: A Computational Study,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2006Lei Zhang ABSTRACT Vertical excitation energies for electronic transitions from the ground state to the first two excited states of phenol, mono- and disubstituted methoxyphenols and methyl-substituted phenols have been characterized with the Time-Dependent Density Functional Theory (TD-DFT), the Complete Active Space Self-Consistent Field method (CASSCF) and the Coupled Cluster with Single and Double Excitations Equation-of-Motion approach (CCSD-EOM) to simulate and interpret experimental ultraviolet absorption spectra. While CASSCF excitation energies for the first two transitions either are grossly overestimated or exhibit a weak correlation with experimental data, both TD-DFT and CCSD-EOM perform very well, reproducing the spectral shifts of both the primary band and secondary band observed upon substitution. The conformational dependence of the calculated excitation energies is generally smaller than the shifts caused by substitution. [source] ChemInform Abstract: Photocyclization of 2-Azido-1-(4-tert-butylphenoxy)-9,10-anthraquinone in the Presence of Substituted Phenols.CHEMINFORM, Issue 18 2008L. S. Klimenko Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Convergent synthesis of two 14C-labeled ,3 -adrenergic receptor agonistsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 8 2006Boris A. Czeskis Abstract The synthesis of ,3 -adrenergic receptor agonists A and B with radiolabeled amide fragment, required for drug disposition studies, was accomplished based on initial formation of 2-(4-(2-amino-2-methylpropyl)phenoxy)-5-[14C]-cyanopyridine by the reaction of 2-bromo-5-iodopyridine with para -substituted phenol, and following cyanation of aromatic iodide with potassium cyanide-[14C]. After the coupling of the resulted amine with glycidyl derivatives of 4-hydroxyindole and 4-hydroxycarbazole, the corresponding nitriles were hydrolyzed with basic hydrogen peroxide to obtain target amides A and B. Copyright © 2006 John Wiley & Sons, Ltd. [source] Ortho Effects in Quantitative Structure Activity Relationships for Lipase Inhibition by Aryl CarbamatesMOLECULAR INFORMATICS, Issue 8 2003Gialih Lin Abstract Ortho -substituted phenyl- N -butyl carbamates (1,11) are synthesized and evaluated for their inhibition effects on Pseudomonas species lipase. Carbamates 1,11 are characterized as pseudo-substrate inhibitors of the enzyme. The logarithms of dissociation constant (Ki), carbamylation constant (k2), and bimolecular inhibition constant (ki) multiply linearly correlate with Hammett substituent constant (,), Taft-Kutter-Hansch ortho steric constant (ES), and Swan-Lupton field constant (F). For ,logKi -, logk2 -, and logki -correlations, values of ,, ,, f, ,XR are 0.2, ,0.06, ,1.7, 0.8; 0.0, 0.0, 1.0, ,0.07; and ,1.8, 7, 0.6, 5; respectively. The enzyme inhibition mechanism is composed of four steps: 1) the first step which is protonation of carbamates 1,11, 2) the second step (Ki1) which involves in the proton 1,3-shift of protonated carbamates 1,11 then the pseudo- trans to cis conformational change, 3) the third step (Ki2) which is formation of a negative charged enzyme-inhibitor tetrahedral intermediate, and 4) the fourth step (k2) which is the carbamylation step. The former three steps are likely composed of the Ki step. There is little ortho steric enhancement effect in the Ki step. From cross-interaction correlations, distance between carbamate and phenyl substituents in transition state for the Ki step is relatively short due to a large ,XR value of 7. The k2 step is insensitive to ortho steric effect. The k2 step involves in departure of leaving group, substituted phenol in which is protonated from the proton 1,3-shift but not from the active site histidine of the enzyme. From cross-interaction correlations, the distance between carbamate and phenyl substituents in transition state for the k2 step is relatively long due to a small ,XR value of 0.6. [source] Solvation effects of H2O and DMSO on the O,H bond dissociation energies of substituted phenolsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 4 2004Yao Fu Abstract Solvation effects on the O,H homolytic bond dissociation energies (BDEs) of substituted phenols were studied. It was demonstrated that the BDEs measured in solution in general do not equal the BDEs in the gas phase. Detailed theoretical analyses indicated that a long-range solvation effect (i.e. the interaction between the solvent and the overall dipole moment of the solute) and a short-range solvation effect (i.e. the hydrogen bonding between the solute and solvent) were both important for the O,H BDEs in water and in DMSO. Neither one of these two factors by itself could fully explain the experimentally observed solvation effect. However, a combination of these two factors, estimated through a semi-continuum solvation model, was shown to be reasonably successful in explaining the experimental results. Copyright © 2004 John Wiley & Sons, Ltd. [source] Potential sources of background contaminants in solid phase extraction and microextractionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 7 2007Robert Stiles Abstract A study to identify the sources of background contamination from SPE, using a C-18 sorbent, and solid-phase microextraction (SPME), using a 70 ,m carbowax/divinylbenzene (CW/DVB) fiber, was carried out. To determine the source of contamination, each material used in the procedure was isolated and examined for their contribution. The solid-phase column components examined were: sorbent material and frits, column housings and each solvent used to elute analytes off the column. The components examined in the SPME procedure were: SPME fiber, SPME vials, water (HPLC grade), and salt (sodium chloride) used to increase the ionic strength. The majority of the background contaminants from SPE were found to be from the SPE sorbent material and frits. The class of contaminants extracted during a blank extraction were phthalates and other plasticizers used during the manufacturing process. All had blank levels corresponding to measured concentrations below 2 ng/mL, except for undecane, which had a concentration of 5.4 ng/mL. The most prevalent contaminants in the SPME blank procedure are 1,9-nonanediol, a mixture of phthalates and highly bis- substituted phenols. All the concentrations were below 2 ng/mL, with the exception of bis (2-ethylhexyl) phthalate, which had concentrations ranging from 5 to 20 ng/mL. [source] Three-step synthesis of arylpolyboronic acids from phenols via organotin compoundsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2007Pablo M. Fidelibus Abstract In this paper we describe a three-step synthesis of aryldi- and triboronic acids starting from phenols. Several substituted phenols (I) were converted into the corresponding aryldiethylphosphates (II) in good to excellent yields. The latter, on reaction with sodium trimethylstannide in liquid ammonia, under irradiation, afforded the aryl- and heteroarylpoly(trimethylstannyl) derivatives in 65,90% yield. The third step is the reaction of the organotin compounds with borane in THF, which leads to the corresponding arylpolyboronic acids in around 80% yield. In order to confirm their structure, some of the diboronic acids were converted into the corresponding pinacol esters. The results obtained in a study on the synthesis of various terphenyls through double and triple Suzuki couplings catalyzed by palladium acetate between the obtained arylpolyboronic acids and various aryl halides are also reported. These reactions proceeded with an average 65% yield, and also enabled us to confirm the structures of some of the diboronic acids. The structure of the new compounds was determined by 1H, 13C and 119Sn NMR spectroscopy, mass spectrometry and IR spectroscopy. Copyright © 2007 John Wiley & Sons, Ltd. 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