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A thorough computational study of a thermal degradation mechanism of 2-ethoxyethanol (2-EE) in the gas phase has been implemented using G3MP2 and G3B3 methods. The stationary point geometries were optimized at the B3LYP functional utilizing the 6-31G(d) basis set. Intrinsic reaction coordinate analysis was performed to determine the transition states on the potential energy surfaces. Nineteen primary different reaction mechanisms, along with the kinetic and thermodynamic parameters, are demonstrated. Most of the thermal degradation mechanisms result in a concerted transition state step as an endothermic process. Among 11 degradation pathways of 2-ethoxyethanol, the formation of ethylene glycol and ethylene is kinetically significant with an activation energy of 269 kJ mol–1 at the G3B3 method. However, the kinetic and thermodynamic calculations indicate that ethanol and ethanal’s formation is the most plausible reaction with an activation barrier of 287 kJ mol–1 at the G3B3 method. For the bimolecular dissociation reaction of 2-ethoxyethanol with ethanol, the pathway that produces ether, H2, and ethanol is more likely to occur with a lower activation energy of 221 kJ mol–1 at the G3B3 method. Thus, 2-EE has experienced a set of complex unimolecular and bimolecular reactions.

Viscosity is the most important characteristic of hydraulic fluid and which is influenced by pressure and temperature. Using statistical methods for correlation analysis and regression, eventual causal relationship between parameters of the Arrhenius-type equation and principally the boiling point of some classical Newtonian liquids is attempted. Empirical validation utilizing data on viscosity of pure Newtonian liquids studied at atmospheric pressure and at different ranges of temperature gives excellent statistical results. Indeed, we found a significant strong correlation between the Arrhenius activation energy (Ea), the Arrhenius temperature (TA), and the boiling point (Tb). Consequently, an original hyperbole-type equation modeling this relationship is proposed which allows the prediction of the boiling temperature and the type of isobaric liquid-vapor diagram through information on viscosity Arrhenius parameters values, only in liquid phase, and will be thus very useful in the handling of engineering data especially for the study of hydraulic components and systems efficiency.

The capability of ccCA, G3, and G3B3 for the prediction of the enthalpies of formation of oxygen fluoride species was evaluated. In addition to these composite methods, the performance of M06 and M06-2X in conjunction with the correlation consistent basis sets (aug-cc-pVnZ), where n = D, T, Q, was also examined for predicting the structures and enthalpies of formation of oxygen fluoride species. A set of various oxygen fluorides were considered, including FOx radicals, FOxH, and FOxF, where x = 1–3. The effects of basis set size and spin contamination were also considered.

The structural stability and internal rotations in cyclopropanecarboxylic acid and cyclopropanecarboxamide were investigated by the DFT-B3LYP and the ab initio MP2 calculations using 6-311G** and 6-311+G** basis sets. The computations were extended to the MP4//MP2/6-311G** and CCSD(T)//MP2/6-311G** single-point calculations. From the calculations the molecules were predicted to exist predominantly in the cis (C O group eclipses the cyclopropane ring) with a cis – trans barrier of about 4–6 kcal/mol. The OCOH torsional barrier in the acid was estimated to be about 12–13 kcal/mol while the corresponding OCNH torsional barrier in the amide was calculated to be about 20 kcal/mol. The equilibrium constant k for the cis ⇔ trans interconversion in cyclopropanecarboxylic acid was calculated to be 0.1729 at 298.15 K that corresponds to an equilibrium mixture of about 85% cis and 15% trans . The vibrational frequencies were computed at the DFT-B3LYP level. Normal coordinate calculations were carried out and potential energy distributions were calculated for the low energy cis conformer of the molecules. Complete vibrational assignments were made on the basis of normal coordinate calculations and comparison with experimental data of the molecules.

The internal rotations in acrylic and methacrylic acids CH2=CX-COOH and their amides CH2=CX-CONH2 (X is H or CH3) were investigated by DFT-B3LYP calculations with 6-311+G** basis set. The potential energy curves were consistent with two minima that correspond to planar cis and trans conformation in the case of the acids (or cis and near-trans forms in the case of the amides). Acrylic acid and acrylamide were predicted to have the cis form as the low and predominant conformation of the molecules. In the case of the methacrylic acid and methacrylamide, the conformational relative stability was predicted to reverse as going from the acrylic to the metha compounds. The trans conformer in methacrylic acid or the near-trans in methacrylamide were predicted to be thermodynamically low energy structures of the molecules. The CCCO rotational barrier was calculated to vary from 4 to 6kcal/mol in the four molecules. The OCOH and OCNH torsional barriers were calculated to be about 13 and 22kcal/mol in the acids and the amides, respectively. The vibrational frequencies of methacrylic acid and methacrylamide were computed at the DFT-B3LYP/6-311+G** level and reliable vibrational assignments were made on the basis of normal coordinate analyses and comparison with experimental data of both molecules in their low energy conformations.