Isomerization energy

Use ) gui to produce the cis and i/rms forms of decalin. Run a PM.f calculation of the energies of these two forms. What is the cis-lmns isomerization energy as calculated by PMIT ... 

B. Dc.war benzene (2) exists as cis and tram isomers. Draw struetures of the two f onris. construct the appropriate input files and determine the c.is-iram isomerization energy of (2). 

Compute the isomerization energy between two forms of C4Hjq iso-butane and n-butane using AMI, PM3 and HF/6-31G(d). How does each model chemistry compare with the observed energy difference (iso-butane minus n-butane) of -1.64 kcal-moT ... 

Compute the isomerization energy between acetaldehyde and ethylene oxide at STP with the QCISD(T)/6-31G(d) model chemistry, and compare the performance of the various model chemistries. Use HF/6-31G(d) to compute the thermal energy corrections. Remember to specify the scaling factor via the Freq=Recxllso option. (Note that we have already optimized the stmcture of acetaldehyde.)... 

The experimental isomerization energy is 27.57 kcal-mol" (ethylene oxide minus acetaldehyde). 

The predicted isomerization energy at various levels of theory are given in the following table ... 

All of the model chemistries predict acetaldehyde to the lower energy isomer. The methods including electron correlation all produce good estimates of the isomerization energy. However, it turns out that the MP2 value is fortuitously good increasing the basis set size would produce a poorer result at the MP2 level. For the... 

MP4 and the two QCISD methods, the predicted isomerization energy v/ould continue to converge toward the experimental value as the basis set size increases. ... 

TABLE V. Isomerization Energies for Butane and Pentane (units kcal/mole)... 

Donath11 has extended these calculations to cyclohexane and cyclopentane and obtained comparably good agreement. It seems safe to conclude that these long-range electron correlation effects account for the isomerization energies of the paraffins which had heretofore remained unexplained. 

Isobutene polymerized, 157 lsoelectronic system, 246 Isomerization energies, for butane, 75 for pentane, 75 Isoprene, 169 Isotactic placement, 172... 

Figure 11. Silyl-allyl complexes as a result of the r)1 to rj3 isomerization from 9a and 9b. The isomerization energies, AEU0, are reported in kcal/mol.

Cremer, D., J. Gauss, E. Kraka, J. F. Stanton, and R. J. Bartlett, A CCSEHT) Investigation of Carbonyl Oxide and Dioxirane. Equilibrium Geometries, Dipole Moments, Infrared Spectra, Heats of Formation, and Isomerization Energies, Chem. Phys. Lett., 209, 547-556 (1993). 

Similar experiments with the JV /V-dimethylaniline analog reveal that the addition of the two methyl groups destabilizes the N-bound form by 33 kJ mol-1 on Os(II) and >50 kJ mol 1 for Os(III). The increased sensitivity to steric effects for Os(III) is thought to be a result of the increased demand for electron density by this higher oxidation state. The differences in isomerization energy for both oxidation states are reflected almost entirely in the rate constants of isomerization from nitrogen-bound to arene-bound complexes. 

Upon increasing the reaction temperature to 350 °C, thermolysis gave slightly less stereospecific results. Thus 1 gave 3 (94%) and 4 (6%) in 84% yield, and 2 gave 3 (10%) and 4 (90%) in 85% yield, respectively. Later Olbrich, Walsh and coworkers estimated the E-Z isomerization energy of 1,2-dimethyl-1,2-diphenyldisilene to be 25.8 5 kcalmol-1 on the basis of these and other data18. 

Another indication of the possible role played by the individual carbene S-T energy splittings in determining energetics and structure in the heteronuclear doubly-bonded systems is obtained by examining the isomerization energies for the process,... 

Figure 1 is an early representation of these three regimes with their distinctive physical and chemical phenomena (3). In this early picture, energy interconversion was considered as a form of isomerization—"energy isomerization"—leading to an expression of the excitation in a form more or less independent of the type of energy input. Vibrational excitation, especially of the lower frequency modes corresponding to intermolecular motion, was considered as the basis for desorption. Activation of surface phonons expresses these ideas in different currency. 

Focusing on the B3LYP/TZVP results, we found that the N2H2 isomerization energy is increased by 10 kJ/mol in complex 1(N2H2) and does not change appreciably in the case of complex 2(N2H2) as compared to the uncoordinated diazene isomers (82). 

For example, based on equation 24, it can be concluded that the isomerization reaction of H2M=CH2 to HMCH3 becomes more exothermic as M becomes heavier, due to the decrease in the M—H bond dissociation energy (Table 3) and in D , and the increase in the DSSE of the MH2 fragments. This conclusion is supported by ab initio calculations. For example, equation 24 leads to predicted isomerization energies of H2M=CH2, M=Si and Ge of 5.8 and —15.3 kcal mol 1, respectively, in good agreement with the ab initio calculated values of 4295 and —15296 kcal mol-1, respectively. 

A. Isomeric Energy Differences, Bond Eneigies, and Divalent State... 

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