Kinetic and Thermodynamic Stability of Naphthalene Oxide and Related Compounds. A Comparative Microcalorimetric and Computational (DFT) Study

Abstract

The kinetics of the acid-catalyzed ring opening of naphthalene 1,2-oxide (5) in highly aqueous media to give naphthols has been measured by heat-flow microcalorimetry. The reaction enthalpy of this aromatization reaction was measured as DeltaH = -51.3 +/- 1.7 kcal mol(-)(1). The unexpectedly low reactivity of naphthalene oxide is suggested to be due to an unusually large thermodynamic stability. A crude estimate of the stabilization effect, approximately 1 kcal mol(-)(1)(not a significant stabilization), is obtained by using the measured reaction enthalpies of structurally related substrates as references. A larger value (2.7 kcal mol(-)(1)) was obtained by calculation using the B3LYP hybrid functional corrected with solvation energies derived from semiempirical AM1/SM2 calculations. The origin of this effect is discussed in terms of homoconjugative stabilization and homoaromaticity. There is a good linear correlation (with slope = 0.63) between the experimentally measured free energy of activation and the calculated enthalpy of carbocation formation in water.

Stereoselective Peterson Olefinations from Bench‐Stable Reagents and N‐Phenyl Imines

“…As neither substrate nor reaction conditions had any significant general influence on the stereochemical outcome of the reaction, a new approach was sought to gain stereocontrol. Previously reported computational studies on the Peterson olefination mechanism have described that, in the absence of a coordinating counter ion, the addition step was rate‐limiting and as such it should be sensitive to steric and electronic influences 10. In an effort to exert such influences in a general manner, ( E )‐ N ‐benzylideneanilines were chosen as alternative electrophiles to aldehydes which could be readily generated by their condensation with inexpensive aniline (Table 2).…”

Self-Assembled Naphthylidene-Containing Schiff Base Anchored Polystyrene Nanocomposites Targeted for Selective Cu(II) Ion Removal from Wastewater

“…With respect to PS resin, a sharp drop in weight appears at an elevated temperature (400–470 °C), indicating thermal degradation of the network structure of PS. Moreover, the introduction of Schiff base molecules slightly reduced the thermal stability of the composite resin, mainly because the presence of the strong hydrophobic naphthalene ring of the Schiff base ensured high thermal stability. , Therefore, self-assembled naphthylidene-containing Schiff base anchored polystyrene nanocomposites could be applied for developing the adsorbent of high thermal stability. However, after adsorption of bivalent copper ions, major losses in weight of the PS-NSB-Cu are found at 300 and 450 °C, which seems that the coordination bond of the copper coordinate chelate breaks at lower temperature.…”

Conversion of 1- and 2-Tetralone Over HY Zeolite

“…The observed isomerization and deoxygenation of 1-naphthol to 2-naphthol and naphthalene over HY zeolite at high temperatures can be explained as follows. Protonation of 1-naphthol by a Brønsted site of the HY zeolite leads to the formation of naphthalene-1,2-oxide intermediate [21][22][23]. Ring opening of this intermediate results in the formation of 2-naphthol.…”

“…Ring opening of this intermediate results in the formation of 2-naphthol. In a parallel path, acid-site assisted hydrogen transfer from carbon deposits or heavies can form a 1-hydroxy-1,2-dihydronaphthalene intermediate [21,24]. This species can be readily dehydrated over the Brønsted sites to form naphthalene.…”