Thermochemistry of alkaline-earth phenoxides

• Published in: The Journal of chemical thermodynamics 2006-03, Vol.38 (3), p.296-303
• Main Authors: Hipólito, Carla, Leal, João Paulo, Guo, Yanzhi, Epple, Matthias
• Format: Article
• Language: English
• Subjects: Chemical thermodynamics; Chemistry; Elements, mineral and organic compounds; Enthalpy of formation; Exact sciences and technology; General and physical chemistry; Lattice energy; Phenoxides; Thermochemical radii; Thermochemistry; Thermodynamic properties
• ISSN: 0021-9614; 1096-3626
• DOI: 10.1016/j.jct.2005.05.016

The standard molar enthalpies of formation of some alkaline-earth metal phenoxides were determined by reaction–solution calorimetry. The results obtained at T = 298.15 K were as follows: Δ f H m ∘ [ M ( OR ) 2 , cr ] / kJ · mol - 1 = - ( 837 . 9 ± 7 . 5 ) [ Mg ( OPh ) 2 ] ; − ( 837 . 4 ± 7 . 2 ) [ Ca ( OPh ) 2 ] ; - ( 888 . 1 ± 7 . 2 ) [ Ca ( O - 2 , 6 - Me 2 Ph ) 2 ] , - ( 828 . 8 ± 7 . 3 ) [ Sr ( OPh ) 2 ] ; - ( 808 . 6 ± 7 . 3 ) [ Ba ( OPh ) 2 ] ; - ( 880 . 7 ± 7 . 3 ) [ Ba ( O - 2 , 6 - Me 2 Ph ) 2 ] . Together with an appropriate Born–Haber cycle, these results allow the calculation of lattice energies for the [M(OR) 2] compounds. The thermochemical radii of the anions OR − were obtained using the Kapustinskii equation and the lattice energies previously determined. A set of lattice energies and standard molar enthalpies of formation for alkaline-earth metal phenoxides [M(OR) 2, M = Mg, Ca, Sr, Ba; R = OPh, 2,6-Me 2OPh], was presented. Estimates for these properties for unmeasured compounds were made based on a model first applied to aliphatic alkaline metal alkoxides.