“…What is found for the isomeric stabilities of the other pairs of 1,3- and 1,4-diderivatized cyclohexanes? The currently found near equality of the enthalpies of formation of the isomeric dithianes is also found for the archival 12 1,3- and 1,4- dimethylcyclohexanes (Ia and Ib) and for 1,3- and 1,4- cyclohexanediones (IIa and IIb), while a significantly higher thermodynamic stability of the 1,3- over the 1,4-isomer is found for the isomeric sets of dioxanes 12 (IIIa and IIIb) and dimethylenecyclohexanes (IVa and IVb) (see Figure ). 5 Experimental enthalpies of formation in the gas state in kJ mol -1 .…”
To understand the relative isomeric stabilities of 1,3- and 1,4-diheterocyclohexanes and the
ultradiagonal strain energy of thiirane, the enthalpies of formation and sublimation of 1,4-dithiane
have been measured. The enthalpy of formation for this compound in the solid state is −69.6 ± 2.3
kJ mol-1, while for the gaseous state, the value is −6.9 ± 2.4 kJ mol. The value for the enthalpy
of sublimation is 63.0 ± 0.6 kJ mol-1. Ab initio molecular orbital calculations at the G2(MP2) and
at G3 levels were performed, and the calculated enthalpies of formation are compared with the
experimental data.
“…What is found for the isomeric stabilities of the other pairs of 1,3- and 1,4-diderivatized cyclohexanes? The currently found near equality of the enthalpies of formation of the isomeric dithianes is also found for the archival 12 1,3- and 1,4- dimethylcyclohexanes (Ia and Ib) and for 1,3- and 1,4- cyclohexanediones (IIa and IIb), while a significantly higher thermodynamic stability of the 1,3- over the 1,4-isomer is found for the isomeric sets of dioxanes 12 (IIIa and IIIb) and dimethylenecyclohexanes (IVa and IVb) (see Figure ). 5 Experimental enthalpies of formation in the gas state in kJ mol -1 .…”
To understand the relative isomeric stabilities of 1,3- and 1,4-diheterocyclohexanes and the
ultradiagonal strain energy of thiirane, the enthalpies of formation and sublimation of 1,4-dithiane
have been measured. The enthalpy of formation for this compound in the solid state is −69.6 ± 2.3
kJ mol-1, while for the gaseous state, the value is −6.9 ± 2.4 kJ mol. The value for the enthalpy
of sublimation is 63.0 ± 0.6 kJ mol-1. Ab initio molecular orbital calculations at the G2(MP2) and
at G3 levels were performed, and the calculated enthalpies of formation are compared with the
experimental data.
“…The resulting geometries (presented in Table 1) are in good agreement with other calculations and solid-state structures. 15 1,4-Cyclohexanedione, 1,3-cyclohexanedione, and cyclohexanone were optimized in their respective diketonic forms, while 1,2cyclohexanedione was optimized in its monoenolic form.…”
Oscillator strengths for C 1 s and 0 1s excitation of gas-phase 1,2-~yclohexanedione, 1,3-cyclohexanedione, 1,4-~yclohexanedione, and cyclohexanone have been derived from electron energy loss spectra recorded under conditions of electric dipole scattering. Spectral assignments have been aided by extended HDckel (EHMO) and HAM/3 calculations. Spectral features characteristic of diketo and monoenol structures are identified. The C 1s and 0 1s spectra clearly indicate that 1,2-cyclohexanedione has a monoenol structure in the gas phase while 1,3-cyclohexanedione is predominantly in the diketonic structure in the gas phase. The latter result resolves an existing literature discrepancy concerning the preferred gas-phase tautomer of 1,3-~yclohexanedione.
“…Unfortunately, the enthalpy of formation data for benzofurans is limited to the parent heterocycle and appears only in a rather inaccessible report 183 . Enthalpy of formation data for butanediones are limited to the 1,4-diphenyl derivative 25 , the monocyclic 1,4-cyclohexanedione 184 and a cage species 185 .…”
Section: Group 4: Titanium Zirconium and Hafniummentioning
Introduction
Group 1: Lithium, Sodium, Potassium, Rubidium and Cesium
Group 2: Beryllium, Magnesium, Calcium, Strontium and Barium
Group 13: Aluminum, Gallium, Indium and Thallium
Group 14: Tin and Lead
Group 11: Copper, Silver and Gold
Group 12: Zinc, Cadmium and Mercury
Group 3: Scandium, Yttrium and the Lanthanides
Actinides
Group 4: Titanium, Zirconium and Hafnium
Group 5: Vanadium, Niobium and Tantalum
Group 6: Chromium, Molybdenum and Tungsten
Group 7: Manganese and Rhenium
Group 8: Iron, Ruthenium and Osmium
Group 9: Cobalt, Rhodium and Iridium
Group 10: Nickel, Palladium and Platinum
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