The enormous acidifying effect of the supersubstituent ᎐ ᎐ NSO 2 CF 3 on the acidity of derivatives of benzenesulfonamide and toluene-p- sulfonamide in the gas phase and in dimethyl sulfoxide

The effect of stepwise replacement of ᎐ ᎐ O oxygen atoms by ᎐ ᎐ NSO 2 CF 3 fragments in the sulfonyl group of toluenep-sulfonamide and benzenesulfonamide on their acidity has been studied in the gas phase and dimethyl sulfoxide (DMSO). Incorporation of the first ᎐ ᎐ NSO 2 CF 3 group into 4-MeC 6 H 4 SO 2 NH 2 increases its gas-phase acidity by 23.6 kcal mol Ϫ1 . Substituting the second ᎐ ᎐ O by the ᎐ ᎐ NSO 2 CF 3 group leads to an additional acidity increase of 10.7 kcal mol Ϫ1 ; the total acidity increase is thus 34.3 kcal mol Ϫ1 (25 powers of ten!). In DMSO solution the total acidity increase is 13 pK a units (17.7 kcal mol Ϫ1 ). These findings are also supported by computational studies using DFT B3LYP at the 6-31ϩG* level and the semiempirical PM3 method. The results of this work have potentially important implications for the design of new strongly acidic catalytic materials

Neuroanatomical heterogeneity and homogeneity in individuals at clinical high risk for psychosis

Individuals at Clinical High Risk for Psychosis (CHR-P) demonstrate heterogeneity in clinical profiles and outcome features. However, the extent of neuroanatomical heterogeneity in the CHR-P state is largely undetermined. We aimed to quantify the neuroanatomical heterogeneity in structural magnetic resonance imaging measures of cortical surface area (SA), cortical thickness (CT), subcortical volume (SV), and intracranial volume (ICV) in CHR-P individuals compared with healthy controls (HC), and in relation to subsequent transition to a first episode of psychosis. The ENIGMA CHR-P consortium applied a harmonised analysis to neuroimaging data across 29 international sites, including 1579 CHR-P individuals and 1243 HC, offering the largest pooled CHR-P neuroimaging dataset to date. Regional heterogeneity was indexed with the Variability Ratio (VR) and Coefficient of Variation (CV) ratio applied at the group level. Personalised estimates of heterogeneity of SA, CT and SV brain profiles were indexed with the novel Person-Based Similarity Index (PBSI), with two complementary applications. First, to assess the extent of within-diagnosis similarity or divergence of neuroanatomical profiles between individuals. Second, using a normative modelling approach, to assess the ‘normativeness’ of neuroanatomical profiles in individuals at CHR-P. CHR-P individuals demonstrated no greater regional heterogeneity after applying FDR corrections. However, PBSI scores indicated significantly greater neuroanatomical divergence in global SA, CT and SV profiles in CHR-P individuals compared with HC. Normative PBSI analysis identified 11 CHR-P individuals (0.70%) with marked deviation (>1.5 SD) in SA, 118 (7.47%) in CT and 161 (10.20%) in SV. Psychosis transition was not significantly associated with any measure of heterogeneity. Overall, our examination of neuroanatomical heterogeneity within the CHR-P state indicated greater divergence in neuroanatomical profiles at an individual level, irrespective of psychosis conversion. Further large-scale investigations are required of those who demonstrate marked deviation.publishedVersio

Ab Initio Calculation of Thermodynamic Functions for CO2 Adsorption in Metal-Organic Frameworks: Entropic Effects of Lateral Interactions

Structure files used in "Ab Initio Calculation of Thermodynamic Functions for CO2 Adsorption in Metal-Organic Frameworks: Entropic Effects of Lateral Interactions

Superacidity of <i>closo</i>-Dodecaborate-Based Brønsted Acids: a DFT Study

The structures and intrinsic gas-phase acidities (GA) of some dodecaborane acids, the derivatives of YB₁₂H₁₁H (Y <b>=</b> PF₃, NH₃, NF₃, NMe₃), B₁₂H₁₂H₂, and B₁₂H₁₂H^– (HA, H₂A, and HA^–, respectively) have been computationally explored with DFT B3LYP method at the 6-311+G** level of theory as new possible directions of creating superstrong Brønsted acids. Depending on the nature and number of the substituents different protonation geometries were investigated. In general, the GA values of the neutral systems varied according to the substituents in the following order: CF₃ < F < Cl and in case of anionic acids: CF₃ < Cl < F. The dodecatrifluoromethyl derivative of H₂A, B₁₂(CF₃)₁₂H₁H₂, emerges as the strongest among the considered acids and is expected to be in the gas phase at least as strong as the undecatrifluoromethyl carborane, CB₁₁(CF₃)₁₁H₁H. The GA values of the respective monoanionic forms of the considered acids all, but the (CF₃)₁₁ derivative, remained higher than the widely used threshold of superacidity. The HA derivatives’ (Y <b>=</b> PF₃, NF₃) GA’s were approximately in the same range as the H₂A acids’. In the case Y <b>=</b> NH₃ or NMe₃ the GA values were significantly higher. Also, the p<i>K</i>_a values of B₁₂H₁₂H₂, CB₁₁H₁₂H, and their perfluorinated derivatives in 1,2-dichloroethane (DCE) were estimated with SMD and cluster-continuum model calculations. The obtained estimates of p<i>K</i>_a values of the perfluorinated derivatives are by around 30 units lower than that of trifluoromethylsulfonylimide, making these acids the strongest ever predicted in solution. The derivatives of B₁₂H₁₂H₂ are as a rule not significantly weaker acids than the respective derivatives of CB₁₁H₁₂H. This is important for expanding practical applicability of this type of acids and their anions, as they are synthetically much more accessible than the corresponding CB₁₁H₁₂^– derivatives

Divergent Access to Histone Deacetylase Inhibitory Cyclopeptides via Late- Stage Cyclopropane Ring Cleavage Strategy. Short Synthesis of Chlamydocin

We present a unified step-economical strategy to access histone deacetylase inhibitory peptides, based on late-stage installation of zinc-binding functionalities via the cleavage of the strained cyclopropane ring in the common pluripotent cyclopropanol precursor. The efficacy of the proposed diversity-oriented approch has been validated by short stereoselective synthesis of a natural product chlamydocin and a number of its analogs.<br /