864 research outputs found
Internet Taxation Without Physical Representation?: States Seek Solution to Stop E-Commerce Sales Tax Shortfall
Influence Of Authority And Message Framing On Compliance With Mental Health Treatment Recommendations
The purpose of this study was to investigate the influence of source authority and message framing on compliance with mental health treatment recommendations. The current study used measures of attitudes and intentions to seek psychological help as well as the likelihood that an individual will request initial counseling information as proxies for observing help-seeking behavior. A pretest and posttest experimental design was implemented. Participants were 273 students at Illinois State University. At pretest, participants completed a demographic questionnaire, the Kessler K6+, the Mental Help Seeking Attitudes Scale (MHSAS), the Mental Help Seeking Intentions Scale (MHSIS), and indicated engagement in past psychological help seeking. At posttest, participants were exposed to a hypothetical mental health treatment recommendation, and recompleted the Kessler K6+, MHSAS, MHSIS, and had the opportunity to request counseling information. No significant main effects were found for source authority on attitudes towards psychological help, intentions to engage in psychological help seeking, or decisions to request counseling information. No significant interaction effects for source authority and message framing were found on intentions to seek psychological help or decisions to request counseling information. Future research could investigate ways to increase mental health treatment utilization by measuring actual help seeking behavior
Transition state energy decomposition study of acetate-assisted and internal electrophilic substitution CâH bond activation by (acac-O,O)_2Ir(X) complexes (X = CH_3COO, OH)
Chelate-assisted and internal electrophilic substitution type transition states were studied using a DFT-based energy decomposition method. Interaction energies for benzene and methane CâH bond activation by (acac-O,O)_2Ir(X) complexes (X = CH_3COO and OH) were evaluated using the absolutely localized molecular orbital energy decomposition analysis (ALMO-EDA). A ratio of ~1.5:1 for forward to reverse charge-transfer between (acac-O,O)_2Ir(X) and benzene or methane transition state fragments confirms âambiphilicâ bonding, the result of an interplay between the electrophilic iridium center and the internal base component. This analysis also revealed that polarization effects account for a significant amount of transition state stabilization. The energy penalty to deform reactants into their transition state geometry, distortion energy, was also used to understand the large activation energy difference between six-membered and four-membered acetate-assisted transition states and help explain why these complexes do not activate the methane CâH bond
Ligand Lone-Pair Influence on Hydrocarbon C-H Activation: A Computational Perspective
Mid to late transition metal complexes that break hydrocarbon C-H bonds by transferring the hydrogen to a heteroatom ligand while forming a metal-alkyl bond offer a promising strategy for C-H activation. Here we report a density functional (B3LYP, M06, and X3LYP) analysis of
cis-(acac)_2MX and TpM(L)X (M=Ir, Ru, Os, and Rh; acac=acetylacetonate, Tp=tris(pyrazolyl)-borate; X=CH_3, OH, OMe, NH_2, and NMe_2) systems for methane C-H bond activation reaction kinetics and thermodynamics.We address the importance of whether a ligand lone pair provides an
intrinsic kinetic advantage through possible electronic d_Ï-p_Ï repulsions for M-OR and M-NR_2 systems versus M-CH_3 systems. This involves understanding the energetic impact of the X ligand group on ligand loss, C-H bond coordination, and C-H bond cleavage steps as well as understanding how the nucleophilicity of the ligand X group, the electrophilicity of the transition metal center, and cis-ligand stabilization effect influence each of these steps.We also explore how spectator ligands and second- versus third-row transition metal centers impact the energetics of each of these C-H activation steps
Experimental realization of catalytic CH_4 hydroxylation predicted for an iridium NNC pincer complex, demonstrating thermal, protic, and oxidant stability
A discrete, air, protic, and thermally stable (NNC)Ir(III) pincer complex was synthesized that catalytically activates the CH bond of methane in trifluoroacetic acid; functionalization using NaIO_4 and KIO_3 gives the oxy-ester
Benzene CâH Bond Activation in Carboxylic Acids Catalyzed by O-Donor Iridium(III) Complexes: An Experimental and Density Functional Study
The mechanism of benzene CâH bond activation by [Ir(ÎŒ-acac-O,O,C^3)(acac-O,O)(OAc)]_2 (4) and [Ir(ÎŒ-acac-O,O,C^3)(acac-O,O)(TFA)]_2 (5) complexes (acac = acetylacetonato, OAc = acetate, and TFA = trifluoroacetate) was studied experimentally and theoretically. Hydrogenâdeuterium (H/D) exchange between benzene and CD_(3)COOD solvent catalyzed by 4 (ÎH^⥠= 28.3 ± 1.1 kcal/mol, ÎS^⥠= 3.9 ± 3.0 cal K^(â1) mol^(â1)) results in a monotonic increase of all benzene isotopologues, suggesting that once benzene coordinates to the iridium center, there are multiple H/D exchange events prior to benzene dissociation. B3LYP density functional theory (DFT) calculations reveal that this benzene isotopologue pattern is due to a rate-determining step that involves acetate ligand dissociation and benzene coordination, which is then followed by heterolytic CâH bond cleavage to generate an iridium-phenyl intermediate. A synthesized iridium-phenyl intermediate was also shown to be competent for H/D exchange, giving similar rates to the proposed catalytic systems. This mechanism nicely explains why hydroarylation between benzene and alkenes is suppressed in the presence of acetic acid when catalyzed by [Ir(ÎŒ-acac-O,O,C^3)(acac-O,O)(acac-C^3)]_2 (3) (Matsumoto et al. J. Am. Chem. Soc. 2000, 122, 7414). Benzene H/D exchange in CF_(3)COOD solvent catalyzed by 5 (ÎH^⥠= 15.3 ± 3.5 kcal/mol, ÎS^⥠= â30.0 ± 5.1 cal K^(â1) mol^(â1)) results in significantly elevated H/D exchange rates and the formation of only a single benzene isotopologue, (C_(6)H_(5)D). DFT calculations show that this is due to a change in the rate-determining step. Now equilibrium between coordinated and uncoordinated benzene precedes a single rate-determining heterolytic CâH bond cleavage step
Orientation Studies in the Dibenzofuran Series
2-Hydroxydibenzofuran on bromination gives 1-bromo-2-hydroxydibenzofuran (m.p., 123.5°) and 2-hydroxy-3-bromo-dibenzofuran (m. p., 143-144°). The corresponding products but in a different ratio are obtained by the bromination of 2-methoxydibenzofuran. The allyl ether of 2-hydroxydibenzofuran rearranges to 1-allyl-2-hydroxydihenzofuran (m.p., 82.5°-83°), the methyl ether of which melts at 68°. Also, 2-hydrozydibenzofuran and benzenediazonium chloride couple to give l-phenylazo-2-hyclroxydibenzofuran. The 3-hydroxydibenzofuran couples to give 2-phenylazo-3- hydroxydibenzofuran (m. p., 166°), the structure of which was established by conversion to 2-bromo-3-hydroxydibenzofuran (m.p., 166°), the structure of which was established by conversion to 2-bromo-3-hydroxydibenzofuran (m.p., 115°-116°)
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