Lithium cations acrolein complexes

Two other Lewis acids were also included in these studies. Lithium cation coordination with acrolein gave a linear, s-trans complex as the most stable structure (Table 4). ° An increase of the s-cis-s-trans gap by 1.4 kcal mol is now difficult to rationalize on steric grounds since the C=0-Li bond is nearly linear. The researchers have suggested that this effect is due to an increase in the electron density on the carbonyl oxygen upon complexation, which in turn would increase nonbonded electron pair-hydrogen repulsion of the alkene termini in the s-cis conformer . A similar effect is observed with (Z)-acrylic acid, where the linear s-trans structure is once again more stable than the s-cis complex by 1.5 kcal mol". ... 

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