Comment on "Causation or only correlation? Application of causal inference graphs for evaluating causality in nano-QSAR models" by N. Sizochenko, A. Gajewicz, J. Leszczynski and T. Puzyn, Nanoscale, 2016, 8, 7203.

In this comment we show that the accuracy of a recent nano-QSAR model for toxicity predictions of metal oxide nanoparticles towards bacteria E. coli can be greatly improved. On one hand, the experimental ionization energies of metal atoms could be substituted for the erroneous semi-empirically derived heat of formation values of metal ions as descriptors to construct a more reliable nano-QSAR model based on weighted linear least-squares fittings.

Definitive thermochemistry and kinetics of the interconversions among conformers of n-butane and n-pentane.

The focal-point analysis (FPA) technique is used for the definitive characterization of conformational interconversion parameters, including activation energy barriers, activation free energies, and kinetic rate coefficients at 298 K, of two n-alkanes, n-butane, and n-pentane, yielding the first complete analysis of their interconversion kinetics. The FPA implementation developed in this study is based on geometry optimizations and harmonic frequency computations carried out with density functional theory methods and single-point energy computations up to the CCSD(T) level of electronic structure theory using atom-centered Gaussian basis sets as large as cc-pV5Z. The anharmonic vibrational computations are carried out, at the MP2/6-31G* level of theory.

Enthalpy Differences of the n-Pentane Conformers.

The energy and enthalpy differences of alkane conformers in various temperature ranges have been the subject for both experimental and theoretical studies over the last few decades. It was shown previously for the conformers of butane [G. Tasi et al.

Benchmarking Experimental and Computational Thermochemical Data: A Case Study of the Butane Conformers.

Due to its crucial importance, numerous studies have been conducted to determine the enthalpy difference between the conformers of butane. However, it is shown here that the most reliable experimental values are biased due to the statistical model utilized during the evaluation of the raw experimental data. In this study, using the appropriate statistical model, both the experimental expectation values and the associated uncertainties are revised.

High-accuracy theoretical thermochemistry of atmospherically important sulfur-containing molecules.

In this study, several sulfur-containing molecules with atmospherical importance were investigated by means of high-accuracy quantum chemical calculations including: HSO, HOS, HOSO2, HSNO, SH, CH2SO, CH2SH, S2COH, and SCSOH. After identifying the stable conformers of the molecules, a coupled-cluster-based composite model chemistry, which includes contributions up to quadruple excitations as well as corrections beyond the nonrelativistic and Born–Oppenheimer approximations, was applied to calculate the corresponding heat of formation (Δ(f)H(0)° and Δ(f)H(298)°) and entropy (S(298)°) values. In most of the cases, this study delivers more reliable estimates for the investigated thermodynamic properties than those reported in previous investigations.

High-accuracy theoretical study on the thermochemistry of several formaldehyde derivatives.

In the case of several formaldehyde derivatives, with importance in atmospheric and combustion chemistry, the currently available thermochemical values suffer from considerably large uncertainties. In this study a high-accuracy theoretical model chemistry has been used to provide accurate thermochemical data including heats of formation at 0 and 298 K and standard molar entropies at 298 K for CF(2)O, FCO, HFCO, HClCO, FClCO, HOCO, and NH(2)CO. For most of the thermochemical quantities studied here, this investigation delivers the best available estimate.

Adiabatic Jacobi corrections on the vibrational energy levels of H2(+) isotopologues.

The effect of an adiabatic approximation, named adiabatic Jacobi correction (AJC) and introduced in J. Chem. Phys.

The effect of electron correlation on the conformational space of melatonin.

The pineal gland hormone melatonin regulates several physiological processes including circadian rhythm and also alleviates oxidative stress-induced degenerative diseases. In spite of its important biological roles, no high level ab initio conformational study has been conducted to reveal its structural features. In this work, the conformational flexibility of melatonin was investigated using correlated ab initio calculations.

Semispectroscopic and quantitative structure-property relationship estimates of the equilibrium and vibrationally averaged structure and dipole moment of 1-buten-3-yne.

Systematic quantum chemical calculations have been performed to obtain precise estimates of the equilibrium and vibrationally averaged molecular structure and electric dipole moment of vinylacetylene (VA, 1-buten-3-yne). Anharmonic (cubic and semi-diagonal quartic) MP2/cc-pVTZ force fields in normal coordinates were computed to account for anharmonic vibrational effects, including zero-point contributions to the rotational constants and the electric dipole moment. A simultaneous weighted least-squares structural refinement was performed, resulting in the best semispectroscopic estimate of the re structure of VA.

1,5-Hydride shift in Wolff-Kishner reduction of (20R)-3beta,20, 26-trihydroxy-27-norcholest-5-en-22-one: synthetic, quantum chemical, and NMR studies.

Heating (20R)-3beta,20,26-trihydroxy-27-norcholest-5-en-22-one (1) with hydrazine and KOH at 160 degrees C completely converted the steroid to a diastereoisomeric mixture of the new (20R,22RS)-27-norcholest-5-ene-3beta,20,22-triols (2). Exclusive formation of 2 suggests that the expected Wolff-Kishner reduction to a methylene group at the C-22 ketone in 1 was diverted to the C-26 position by a 1,5-hydride shift. All attempts under acid conditions failed to produce a C-22 phenyl hydrazone from 1.