Several possible scales of steric effects of the alkyl groups were suggested on the basis of isodesmic model reactions, in which a sterically crowded compound is formally synthesized from simpler derivatives. The reaction energies were calculated within the framework of the density functional theory at the level B3LYP/6-311+G(d.p)//B3LYP/6-311+G(d.p) for 6 model systems and 7 various alkyl grou...

We report the proton affinities (PAs) and gas-phase basicities (GBs) of pyrogallol (1,2,3-trihydroxybenzene) phloroglucinol (1,3,5-trihydroxybenzene), as determined by high level quantum chemical calculations a series isodesmic transfer reactions. These yet unmeasured values have relevance to release active species from nanocarriers derived calixarene family macrocycles. The PAs GBs obtained fo...

Cyclododecane preferentially adopts a square-like geometry, giving rise to corner and edge methylene (CH2) groups, whose hydrogens assume different orientations. In CH2 can be inward- (endo) outward-looking (exo) the ring. Herein, we have quantum-chemically studied replacement of two in cyclododecane with iodines at relative positions 1,4, 1,5, 1,6, 1,7. Intramolecular interactions are only sli...

This work entails a detailed modeling and experimental study for the oxidation kinetics of acetaldehyde (CH3CHO) its interaction with NOx. The ignition behavior CH3CHO/O2/Ar has been investigated in shock tube over temperature range 1149 to 1542 K, equivalence ratios 0.5 1.0 pressures near 1.2 bar. Absorbance–time profiles were recorded using mid-IR laser during autoignition measurements. A com...

Detailed theoretical investigation has been performed on the mechanism, kinetics and thermochemistry of the gas phase reactions of CF3CH2OCH3 (HFE-263fb2) with OH radicals using ab-initio and DFT methods. Reaction profiles are modeled including the formation of pre-reactive and post-reactive complexes at entrance and exit channels, respectively. Our calculations reveal that hydrogen abstraction...

MINDO-Forces calculations with complete geometry optimization have been performed on nitromethane, aci-nitromethane and X-substituted nitromethane and aci-nitromethane (X = F, OH, NH2, CH3, CN, CF3, NO2, CHO). It is found that nitromethane is more stable than aci-nitromethane by 9.337 kcal/mol. This agrees with theoretical calculations. Thermodynamically, substituted acinitro tautomers are more...

Four series of hydrogen bonded complexes of formamide and substituted benzoic acids and benzoates were studied in the light of substituent effect on intermolecular interactions. The analysis based on energy of interaction, geometry, QTAIM-derived properties of hydrogen bond critical point and energy of hydrogen bonds were made and discussed. The opposite effect of the substituent on hydrogen bo...

Density functional theory (DFT) calculations have been performed to calculate the optimized geometries of stepwise fluorinated methylenecyclopropanes and 1-methylcyclopropenes. Increasing the number of fluorine atoms caused a destabilization of methylenecycopropane. Perfluorinated 1-methylcyclopropene was found to be present in substantial concentration. This is supported by calculations of the...

Elastin-like polypeptides (ELPs) are large, nonpolar polypeptides under investigation as components of a novel drug delivery system. ELPs are soluble at low temperatures, but they desolvate and aggregate above a transition temperature (TT). This aggregation is being utilized for targeting systemically delivered ELP-drug conjugates to heated tumors. We previously examined the structural, thermod...

Serious and systematic errors with popular density functionals occur for isodesmic stabilization energies of n-alkanes, isomerization, and dimerization energies of hydrocarbons and geometries of sterically overcrowded aromatic systems. These functionals are too biased toward the correct description of free atoms. Changing two parameters within the Perdew-Burke-Ernzerhof approximation leads to a...