| Abstract
| - A DFT analysis of the condensation of monomeric methyllithium and lithium dimethylamide (LMA),as well as their homo and hetero dimers, on formaldehyde and acetaldehyde is reported. A stablecomplex, exhibiting a directional interaction between a lone pair of the oxygen on the aldehydeand a lithium, is first found. At this stage, the aldehyde carbonyl and the Li−X (X = C or N) bondslie in the same plane. To proceed, the condensation reaction has to go through a transition statethat mainly consists of a rotation of the aldehyde plane, placing it perpendicular to the C−C orC−N forming bond. The reaction then leads, in a strongly exothermic final step, to the additionproduct that is a lithium alcoholate or α-amino alcoholate, associating into an hetero-aggregatewith the remaining moiety of the initial dimer. From the relative heights of the activation barriers,it appears that, for the heterodimer MeLi−LMA, the formation of the C−N bond should bekinetically favored over the C−C one, while the lithium ethylate resulting from the C−C bindingis the thermodynamic product. A decomposition of the activation energy barriers has been carriedout in order to determine the physicochemical forces responsible for the variation of the condensationactivation barriers with the structure of the final species formed. The results obtained are discussedin relation with corresponding experimental data.
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