Isomerizations of bicyclo[2.1.0]pent-2-ene and tricyclo[,5)]pentane into cyclopenta-1,3-diene: A computational study by DFT and high-level ab initio methods

Özkan, İlker
Balci, M
The thermal isomerizations of bicyclopentene (bcp) and tricyclopentane (tcp) into cyclopentadiene (cp) are investigated by a combination of DFT, CASSCF, CASSCF-MP2, and CR-CCSD(T) methods. Coupled-clusters and B3LYP methods predicted the reaction enthalpies excellently whereas the MCSCF method worked well only when dynamic correlation energy was taken into account. Both processes are concerted, and the reaction paths pass through transition states with high biradical character. Measures of biradical character in DFT and ab initio methods are discussed. The activation enthalpy in the rearrangement of bcp into cp was predicted by the CR-CCSD(T) method to be 25.5 kcal/mol, in good agreement with experiment. The UB3LYP functional also performed well in this case despite the high spin contamination that was present in the singlet biradicaloid transition state. The reaction enthalpy for the conversion of tcp into cp was predicted to be -63.7 kcal/mol. The transition state involved in the isomerization of tcp was found to be nearly degenerate with the triplet state causing less certainty in the estimated activation enthalpy of 48.3 kcal/mol.


A linear variation of the thermal expansivity with the isothermal compressibility for ammonia solid III near the melting point
Yurtseven, Hasan Hamit (2010-01-01)
The thermal expansivity alpha (p) is related to isothermal compressibility kappa (T) at various pressures for constant temperatures of 254.6, 274 and 297.5 K close to the melting pressure in ammonia solid III. By analyzing the experimental data for kappa (T) according to a power-law formula, a linear variation of alpha (p) with the kappa (T) is established here close to the solid-liquid transition in ammonia. Anomalous behavior of thermal expansivity alpha (p) and the isothermal compressibility kappa (T) ne...
Temperature dependence of the thermal expansivity and the specific heat near the nematic-isotropic (NI) phase transition in PAA
Kilit, E.; Yurtseven, Hasan Hamit (Elsevier BV, 2008-02-15)
Temperature dependence of the thermal expansivity alpha(p) and the specific heat C-p has been studied for the nematic-isotropic (NI) phase transition (T-NI=133.9 degrees C) of PAA.
Raman frequency shifts for the rotatory lattice mode close to the melting point in ammonia solid I
Karacali, H; Yurtseven, Hasan Hamit (American Chemical Society (ACS), 2005-09-08)
We correlate here the thermal expansivity alpha(p) to the frequency shifts 1/v(partial derivative v/partial derivative P)(T) for the rotatory lattice (librational) mode in ammonia solid I close to the melting point. This is carried out for the pressures of 0, 1.93, and 3.07 kbar at various temperatures for this solid structure. By obtaining linear plots of alpha(p) versus 1/v(partial derivative v/partial derivative P)(T) for the pressures studied, we extract the values of the slope dP(m)/dT according to our...
Ferromagnetic and antiferromagnetic properties in layered structures (La0.6Nd0.4Mn2Si2)
Doğan, Ezgi; Emre, B.; Yurtseven, Hasan Hamit (2015-06-05)
Temperature dependences of the magnetization (ferromagnetic) and the staggered magnetization (anti-ferromagnetic) are analyzed for various ferromagnetic (FM) and antiferromagnetic (AF) phases of the layered structure of La0.6Nd0.4Mn2Si2 using the experimental data at a constant magnetic field of 50 Oe. For this analysis, a mean field model with the quadratic coupling between the magnetization (FM) and the staggered magnetization (AF) is considered and the expressions derived from the mean field model for th...
Kinetics of the substitution of norbornadiene in tetracarbonyl(norbornadiene)molybdenum(0) by 2,2 '-3-bipyridine
Kayran, C; Okan, E (2001-03-01)
The kinetics of the thermal substitution of norbornadiene (nbd) by 2,2 ' -bipyridine (2,2 ' bipy) in (CO)(4)Mo(C7H9) was studied by quantitative FT-IR and UV-VIS spectroscopy. The reaction rate exhibits first-order dependence on the concentration of the starting complex, and the observed rate constant depends on the concentration of both leaving nbd and entering 2,2 ' -bipy ligand. The mechanism was found to be consistent with the previously proposed one, where the rate determining step is the cleavage of o...
Citation Formats
İ. Özkan and M. Balci, “Isomerizations of bicyclo[2.1.0]pent-2-ene and tricyclo[,5)]pentane into cyclopenta-1,3-diene: A computational study by DFT and high-level ab initio methods,” JOURNAL OF PHYSICAL CHEMISTRY A, pp. 507–514, 2004, Accessed: 00, 2020. [Online]. Available: