Energy reaction, relativistic effects

These results are in accord with the long-accepted mechanism for the SN2 reaction in the gas phase experiments using ion cyclotron resonance were interpreted in the way shown for the calculations of Fig. 2 It is not possible to explain the observed rates on the basis of a single-well potential [38] the profile in Fig. 2 is called a double-well potential. Quantitative information comes from benchmark calculations by Bento et al., who even checked for relativistic effects, which were found to be negligible [39]. CCSD(T)/aug-cc-PVQZ (Sections 5.4.3 and 5.3.3 ) gave relative energies of 44 and +10.5 kJ mol-1, compared to —39 and —2.1 kJ mol-1 at out modest computational level. That the transition state lies slightly... 

Energies of the decomposition reactions MX4 —> MX2 + X2 and MX2 — M + X2 (X = H, F and Cl) for group-14 elements were calculated at the PP CCSD(T) and DHF levels [96,52], The results show a decreasing trend in the stability of the 4+ oxidation state in the group in agreement with the predictions of [150] based on atomic calculations and simple models of bonding. The instability was shown to be a relativistic effect. The neutral state was found to be more stable for element 114 than that for Pb. Thus, element 114 is expected to be less reactive than Pb, and as reactive as Hg. The possibility of the existence of 114F62 is considered [96]. 

To study the stability of higher oxidation states, energies of the MFe" MF4 + F2 and MF4 MF2 + F2 (M = Cu, Ag, Au and element 111) decomposition reactions were calculated at the PP MP2 and CCSD levels of the theory [133,166]. The results confirmed that relativistic effects stabilize higher oxidation states in the high-coordination compounds of element 111 due to a destabilization of the 6d orbitals and their larger involvement in the bonding. 

The relativistic effects play an important role in a chemical reaction and influence its energy and the reaction path. It has been observed that if the dominant relativistic effect comes through the s populations, relativistic effects on reaction energies should be large when there is a signiflcant change in s population [12], This is the case in the reaction studied by Dyall [27]... 

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