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The α-effect, an enhanced reactivityof nucleophiles witha lone-pair adjacent to the reaction center, has been studied in solutionfor several decades. The gas-phase α-effect has recently beendocumented in studies of SN2 reactions as well as in competingreactions for both bare and microhydrated anions. In the present workwe extend our studies of the significance of microsolvation on theα-effect, employing methanol as the solvent, in the expectationthat the greater stability of the methanol cluster relative to thewater cluster will lower the reactivity and thereby allow studiesover a wider efficiency range. We compare the gas-phase reactivityof the microsolvated α-nucleophile HOO–(CH3OH) to that of microsolvated normal alkoxy nucleophiles, RO–(CH3OH) in reactions with CH3Cl and CH3Br. The results reveal enhanced reactivity ofHOO–(CH3OH) toward both methyl halidesrelative to the normal nucleophiles, and clearly demonstrate the presenceof an α-effect for the microsolvated α-nucleophile. Thehighly exothermic reactions with methyl bromide result in a smallerBrønsted βnucvalue than observed for methylchloride, and the α-effect in turn influences the reactionswith methyl chloride more than with methyl bromide. Computationalinvestigations reveal that reactions with methyl bromide proceed throughearlier transition states with less advanced bond formation comparedto the related reactions of methyl chloride. In addition, solventinteractions for HOO–are quite different from thosewith the normal nucleophiles at the transition state, indicating thatdifferential solvation may well contribute to the α-effect.The greater thermodynamic and kinetic stability of the anion-methanolclusters relative to the anion-water clusters accounts well for thedifferences in the influence of solvation with the two protic polarsolvents. [ABSTRACT FROM AUTHOR]

The α-effectenhanced reactivity of nucleophiles with a lone-pair adjacent to the attacking centerwas recently demonstrated for gas-phase SN2 reactions of HOO−, supporting an intrinsic component of the α-effect. In the present work we explore the gas-phase reactivity of microsolvated nucleophiles in order to investigate in detail how the α-effect is influenced by solvent. We compare the gas-phase reactivity of the microsolvated α-nucleophile HOO−(H2O) to that of microsolvated normal alkoxy nucleophiles, RO−(H2O), in reaction with CH3Cl using a flowing afterglow-selected ion flow tube instrument. The results reveal enhanced reactivity of HOO−(H2O) and clearly demonstrate the presence of an α-effect for the microsolvated α-nucleophile. The association of the nucleophile with a single water molecule results in a larger Brønsted βnuc value than is the case for the unsolvated nucleophiles. Accordingly, the reactions of the microsolvated nucleophiles proceed through later transition states in which bond formation has progressed further. Calculations show a significant difference in solvent interaction for HOO− relative to the normal nucleophiles at the transition states, indicating that differential solvation may well contribute to the α-effect. The reactions of the microsolvated anions with CH3Cl can lead to formation of either the bare Cl− anion or the Cl−(H2O) cluster. The product distributions show preferential formation of the Cl− anion even though the formation of Cl−(H2O) would be favored thermodynamically. Although the structure of the HOO−(H2O) cluster resembles HO−(HOOH), we demonstrate that HOO− is the active nucleophile when the cluster reacts. [ABSTRACT FROM AUTHOR]

Gas-phasevibrational spectra of 2-aminoethanol and 3-aminopropanolwere recorded up to the third OH-stretching overtone using Fouriertransform infrared spectroscopy, cavity ringdown spectroscopy, andintracavity laser photoacoustic spectroscopy. The experimental investigationwas supplemented by local mode calculations, and the intramolecularinteractions were investigated using atoms in molecules (AIM) andnoncovalent interactions (NCI) theories. All calculations were performedat the CCSD(T)-F12a/VDZ-F12 level of theory. For both compounds themost abundant conformer has a structure that allows for hydrogen bondinteraction from the OH group to the N atom of the amino group (OH–N).The spectra show signals from both hydrogen bonded and free OH stretches,implying the presence of several conformers. We observe hydrogen-bond-likeinteractions in both compounds. The red shift of the bonded OH-stretchingfrequency and intensity enhancement of the fundamental transitionsuggest that the hydrogen bond interaction is more pronounced in 3-aminopropanol.AIM analysis supports the presence of a hydrogen bond in 3-aminopropanolbut not in 2-aminoethanol, whereas NCI analysis shows hydrogen bondingin both compounds with the stronger interaction found in 3-aminopropanol. [ABSTRACT FROM AUTHOR]

To investigate whether acquisition of the perspective-marking grammar of complement-clause constructions supports progression in children's false-belief reasoning, we conducted a training study with 76 English-speaking 3-year-olds from the North-West of England (age range: 3;0-3;10 years, 50% female, 80% White). Children were randomly assigned to one of three maximally comparable training conditions, and in a 4-week eight-session program, all children participated in the same training activities with mental-state contrasts. Depending on condition, activities were mediated linguistically with either simple clauses, first-person complements, or third-person complements. The study addressed critical confounds in previous training studies by avoiding the use of complement clauses in false-belief tests and controlling individual differences in memory, executive functioning, general language, and pretest proficiency with complement clauses. The results yielded strong support for the hypothesis of a causal influence of complement-clause exposure on false-belief progression, as children trained with first-person complements advanced significantly more in false-belief reasoning from pretest to posttest than children trained with simple clauses. Examining the roles of first- and third-person complements, a direct comparison between progression in the two complement-clause conditions showed no significant difference, but only children trained with first-person complements progressed significantly more than children in the control condition trained with simple clauses. Follow-up analyses suggested that first- and third-person complements each support false-belief progression at different stages of development. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Formation of oxidized products from Δ 3 -carene (C 10 H 16 ) ozonolysis and their gas-to-particle partitioning at three temperatures (0, 10, and 20 °C) under dry conditions (<2% RH) and also at 10 °C under humid (78% RH) conditions were studied using a time-of-flight chemical ionization mass spectrometer (ToF-CIMS) combined with a filter inlet for gases and aerosols (FIGAERO). The Δ 3 -carene ozonolysis products detected by the FIGAERO-ToF-CIMS were dominated by semivolatile organic compounds (SVOCs). The main effect of increasing temperature or RH on the product distribution was an increase in fragmentation of monomer compounds (from C 10 to C 7 compounds), potentially via alkoxy scission losing a C 3 group. The equilibrium partitioning coefficient estimated according to equilibrium partitioning theory shows that the measured SVOC products distribute more into the SOA phase as the temperature decreases from 20 to 10 and 0 °C and for most products as the RH increases from <2 to 78%. The temperature dependency of the saturation vapor pressure (above an assumed liquid state), derived from the partitioning method, also allows for a direct way to obtain enthalpy of vaporization for the detected species without accessibility of authentic standards of the pure substances. This method can provide physical properties, beneficial for, e.g., atmospheric modeling, of complex multifunctional oxidation products.

The formation of secondary organic aerosol (SOA) from the structurally similar monoterpenes, α-pinene and Δ 3 -carene, differs substantially. The aerosol phase is already complex for a single precursor, and when mixtures are oxidized, products, e.g., dimers, may form between different volatile organic compounds (VOCs). This work investigates whether differences in SOA formation and properties from the oxidation of individual monoterpenes persist when a mixture of the monoterpenes is oxidized. Ozonolysis of α-pinene, Δ 3 -carene, and a 1:1 mixture of them was performed in the Aarhus University Research on Aerosol (AURA) atmospheric simulation chamber. Here, ∼100 ppb of monoterpene was oxidized by 200 ppb O 3 under dark conditions at 20 °C. The particle number concentration and particle mass concentration for ozonolysis of α-pinene exceed those from ozonolysis of Δ 3 -carene alone, while their mixture results in concentrations similar to α-pinene ozonolysis. Detailed offline analysis reveals evidence of VOC-cross-product dimers in SOA from ozonolysis of the monoterpene mixture: a VOC-cross-product dimer likely composed of the monomeric units cis -caric acid and 10-hydroxy-pinonic acid and a VOC-cross-product dimer ester likely from the monomeric units caronaldehyde and terpenylic acid were tentatively identified by liquid chromatography-mass spectrometry. To improve the understanding of chemical mechanisms determining SOA, it is relevant to identify VOC-cross-products.

The first study of pseudo-bimolecular cycloaddition reaction dynamics in the gas phase is presented. We used femtosecond time-resolved photoelectron spectroscopy (TRPES) to study the [2+2] photocycloaddition in the model system pseudo-gem-divinyl[2.2]paracyclophane. From X-ray crystal diffraction measurements we found that the ground-state molecule can exist in two conformers; a reactive one in which the vinyl groups are immediately situated for [2+2] cycloaddition and a nonreactive conformer in which they point in opposite directions. From the measured S(1) lifetimes we assigned a clear relation between the conformation and the excited-state reactivity; the reactive conformer has a lifetime of 13 ps, populating the ground state through a conical intersection leading to [2+2] cycloaddition, whereas the nonreactive conformer has a lifetime of 400 ps. Ab initio calculations were performed to locate the relevant conical intersection (CI) and calculate an excited-state [2+2] cycloaddition reaction path. The interpretation of the results is supported by experimental results on the similar but nonreactive pseudo-para-divinyl[2.2]paracyclophane, which has a lifetime of more than 500 ps in the S(1) state., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)