Theoretical study on the mechanisms and kinetics of the β-elimination of 2,2-dihaloethyltrihalosilanes (X = F, Cl, Br) compounds: a DFT study along with a natural bond orbital analysis

The β-elimination kinetics of 2,2-dihaloethyltrihalosilanes in the gas phase has been studied computationally using density functional theory (DFT) along with the M06-2x exchange–correlation functional and the aug-cc-pVTZ basis set. The calculated energy profiles have been supplemented with calculations of rate constants under atmospheric pressure and in the fall-off regime, by means of transition state theory (TST), variational transition state theory (VTST), and statistical Rice–Ramsperger–Kassel–Marcus (RRKM) theory. Activation energies and rate constants obtained using the M06-2x/aug-cc-pVTZ approaches are in good agreement with the available experimental data. Analysis of bond order, natural bond orbitals, and synchronicity parameters suggests that the β-elimination of the studied compounds can be described as concerted and slightly asynchronous. The transition states of these reactions correspond to four-membered cyclic structures. Based on the optimized ground state geometries, a natural bond orbital (NBO) analysis of donor–acceptor interactions also show that the resonance energies related to the electronic delocalization from σC1−C2 bonding orbitals to σ∗C2−Si3 antibonding orbitals, increase from 2,2-difluoroethyltrifluorosilane to 2,2-dichloroethyltrichlorosilane and then to 2,2-dibromoethyltriboromosilane. The decrease of σC1−C2 bonding orbitals occupancies and increase of the σ∗C2−Si3 antibonding orbitals occupancies through σC1−C2→σ∗C2−Si3 delocalizations could facilitate the β-elimination of the 2,2-difluoroethyltrifluorosilane compound, compared to 2,2-dichloroethyltrichlorosilane and 2,2-dibromoethyltriboromosilane.energy barriers; β-elimination processes; rate constants; NBO; reaction mechanism

Public sector corruption and the probability of technological disasters

A growing number of studies have explored the influence of institution on the outcomes of disasters and accidents from the viewpoint of political economy. This paper focuses on the probability of the occurrence of disasters rather than disaster outcomes. Using panel data from 98 countries, this paper examines how public sector corruption is associated with the probability of technological disasters. It was found that public sector corruption raises the probability of technological disasters. This result is robust when endogeneity bias is controlled

Long-term changes in sediment type and cavernicolous bivalve assemblages in Daidokutsu submarine cave, Okinawa Islands: evidence from a new core extending over the past 7,000 years

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Confidence through consensus: a neural mechanism for uncertainty monitoring

Models that integrate sensory evidence to a threshold can explain task accuracy, response times and/nconfidence, yet it is still unclear how confidence is encoded in the brain. Classic models assume that/nconfidence is encoded in some form of balance between the evidence integrated in favor and against/nthe selected option. However, recent experiments that measure the sensory evidence’s influence on/nchoice and confidence contradict these classic models. We propose that the decision is taken by many/nloosely coupled modules each of which represent a stochastic sample of the sensory evidence integral./nConfidence is then encoded in the dispersion between modules. We show that our proposal can account/nfor the well established relations between confidence, and stimuli discriminability and reaction times,/nas well as the fluctuations influence on choice and confidence.This work was supported by CONICET-Argentina (to L.P. and M.S.), the Spanish Ministry of Science and Technology Grant BFM2002-02042 (to D.C. and J.L.R.), by National Science Foundation Grant DMS-0245242 (to C.F.), by Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR - 2014SGR856 to AI and GD), by MINECO (PSI2013-42091-P to AI and GD) and the James McDonnell Foundation 21st Century Science Initiative in Understanding Human Cognition - Scholar Award (to M.S.)