Trans-cis isomerization of hydroxymethylene and formaldehyde formation

In principle the trans-cis isomerization can occur with the hydrogen motion in plane or out-of plane. We have explored these two possibilities finding that the out of plane way requires a slightly lower barrier [43]. In agreement with all other 

The agreement is also very good with previous DF studies [21,44] in which the Baker s procedure is used to find the TS and also with HF-MP4 results [47,48], The barriers for isomerizations are found to be practically the same (83.1 and 83.2 

Relative stabilities of isomers and isomerization barriers with respect to formaldehyde from experiment and several levels of theory. All values are in kcal/mol. 

The oxidation of methyl radical with molecular oxygen is a complicated process that involves different competing reactions. The first step of CH3 oxidation is the formation, without energy barrier, of the methylperoxy radical that is a common intermediate for the subsequent reactions. In the pathway that give CH2O + OH as final products, the existence of a CH300 CH200H isomerization process is postulated to occur. Because of the well known difficulties in the theoretical characterization of radical reactions and the importance of the role that these reactions plays in the combustion processes, we have undertaken the study of the entire reaction profile with both HF-CI and DF methods. The localization of the transition state for the above mentioned isomerization at ab-initio HF level is possible only when the correlation is considered [49]. 

In both cases the TS appears to be an asymmetric four center cycle in which both C-H and 0-0 bonds are longer than in the two minima. The NLSD energy barrier is 49.1 kcal/mol. For purpose of comparison, we have determined this energy barrier also at MP2/MP2, MP2//MP4 and MP2//QCISD(T) levels of theory. The results are 51.7, 52.4 and 52.6 Kcal/mol respectively. 

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