Structural and Energetic Insights on Two Dye Compounds: 1-Acetyl-2-Naphthol and 2-Acetyl-1-Naphthol

Abstract

The energy involved in the structural switching of acyl and hydroxyl substituents in the title compounds was evaluated combining experimental and computational studies. Combustion calorimetry and Knudsen effusion techniques were used to determine the enthalpies of formation, in the crystalline state, and of sublimation, respectively. The gas-phase enthalpy of formation of both isomers was derived combining these two experimental data. Concerning the computational study, the G3(MP2)//B3LYP composite method was used to optimize and determine the energy of the isomers in the gaseous state. From a set of hypothetical reactions it has been possible to estimate the gas-phase enthalpy of formation of the title compounds. The good agreement between the experimental and computational gas-phase enthalpies of formation of the 1-acetyl-2-naphthol and 2-acetyl-1-naphthol isomers, provided the confidence for extending the computational study to the 2-acetyl-3-naphthol isomer. The structural rearrangement of the substituents in position 1 and 2 in the naphthalene ring and the energy of the intramolecular hydrogen bond are the factors responsible for the energetic differences exhibited by the isomers. The gas phase tautomeric keto « enol equilibria of the o-acetylnaphthol isomers were analyzed using the Boltzmann’s distribution.

Revision and Extension of a Generally Applicable Group-Additivity Method for the Calculation of the Standard Heat of Combustion and Formation of Organic Molecules

“…An especially extended amount of research has been done with hydrocarbons including alkanes, alkenes, alkynes, and aromatics , forming the core of the various carbon groups. In addition, many data have dealt specifically with alcohols and phenol derivatives [61][62][63][64][65][66][67][68][69][70][71][72][73][74], ethers [75][76][77][78][79][80][81][82][83][84], carbaldehydes [85][86][87][88][89][90][91][92][93][94], ketones [95][96][97][98][99][100][101][102][103][104][105][106][107][108][109]...…”