High-accuracy extrapolated ab initio thermochemistry of the propargyl radical and the singlet C(3)H(2) carbenes.
Total atomization energies and enthalpies of formation (0 and 298.15 K) are evaluated using the high-accuracy extrapolated ab initio thermochemistry (HEAT) scheme for the two stable singlet C(3)H(2) carbenes [cyclopropenylidene (c-C(3)H(2)) and propadienylidene (vinylidencarbene, l-C(3)H(2))], as well as for the 2-propynyl (propargyl, C(3)H(3)) radical. In the case of propargyl, the HEAT protocol predicts an enthalpy of formation of 354.9 +/- 1.0 kJ mol(-1) for 0 K; corresponding values of 498.1 +/- 1.0 and 555.6 +/- 1.0 kJ mol(-1) are estimated for c-C(3)H(2) and l-C(3)H(2). Additional consideration of temperature corrections leads to estimates of 352.2 +/- 1.0, 497.1 +/- 1.0, and 556.7 +/- 1.0 kJ mol(-1) for the heats of formation at 298.15 K of the propargyl radical, c-C(3)H(2), and l-C(3)H(2), respectively. Potential strategies for simplifying the HEAT protocol are also investigated and shown to have negligible impact on accuracy.
Vázquez
Juana
J
Center for Theoretical Chemistry, Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA. juana@mail.cm.utexas.edu
Harding
Michael E
ME
Gauss
Jürgen
J
Stanton
John F
JF
D003198:Computer Simulation; D005609:Free Radicals / Q000737:chemistry; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008956:Models, Chemical; D011789:Quantum Theory; D013816:Thermodynamics
D005609:Free Radicals; C030011:carbene; D008697:Methane