Orthoeffect and steric inhibition of resonance: basicities of methyl-substituted acetophenones

Estimate of Hyperconjugation Strength in Alkylaromatics and Unsaturated Hydrocarbons Derived from Refractometric Data

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A retrospective view of exaltation of refraction observed for many unsaturated and aromatic compounds demonstrates that this physical phenomenon is undeservedly considered only as a qualitative measure of conjugation. This mini-review discusses numerous papers by the author that have been published earlier in inaccessible periodicals and collections of scientific papers. Using a great number of illustrations, the author shows that this parameter can be successfully used for quantitative estimate of resonance effects in organic and polymer chemistry. The methods for derivation of strictly additive atomic and group refraction constants are described; these constants were subsequently used as a tool that allowed quantitative estimation of resonance effects in mono-, di-, tri- and polyalkylbenzenes, alkylnaphthalenes, some alkyl derivatives of unsaturated hydrocarbons. These effects cause strictly fixed increase in refraction of carbon atoms in different structural modifications (graphene, fullerene, diamond) and in polycyclic aromatic hydrocarbons. The relevant results regarding quantitative estimation of degree of steric inhibition of resonance in sterically hindered ortho-dialkylbenzenes, 1,2,3- trialkyl-, 1,2,3,4-tetraalkyl-, and 1,2,3,4,5-polyalkylbenzenes accumulated by the author are summarized.

The use of chemical shift calculations in the conformational analysis of substituted benzenes

MM/QM calculations of ¹³C chemical shifts can determine the conformations and electron densities in organic compounds.

Single and double intramolecular proton transfers in the electronically excited state of flavone derivatives

3,7-Dihydroxyflavone derivatives containing carbonyl fragments were synthesized. Results of the fluorescent spectroscopy investigations indicate that one of them undergoes Excited State Intramolecular Double Proton Transfer (ESIDPT).

Proton affinity of para-substituted acetophenones in gas phase and in solution: a theoretical study

The gas phase proton affinities PA and basicities GB for a series of para-substituted acetophenones weak bases (B) p.X-C(6)H(4)CO*CH(3) with X=H, F, Cl, Br, I, Me, CF(3), CN, NO(2), OCH(3), NH(2), CH(2)OH, N(CH(3))(2), OH, [Formula: see text], … have been calculated at 298.15 K at the density functional theory DFT/B3LYP level with a 6-311++G (2d,2p) basis set. Conformational results lead to only one stable planar conformer for both unprotonated compounds and their O*-protonated forms. Satisfactory accuracy and computational efficiency could be reached if the computed PAs are scaled by a factor 0.983. Protonation at more than one site is discussed and the carbonyl oxygen atom is found to be the preferential protonated site rather than the substituent X. The calculated gas phase PAs show a good agreement with the experimental available data. The electron-donating/electron-withdrawing nature of the substituents has an enormous influence upon the thermochemical and structural properties. The influence of environment on the proton affinity has been studied by means of SCRF solvent effect computations using PCM solvation model for two solvents: water and SO(2)CI(2). Confrontation between computed and experimental pK(B) values exhibits better agreement in aqueous solution than in organic solvent.