B Fluorine atoms and fluoroalkyl substituents adjacent to the carbanion centre

B Fluorine atoms and fluoroalkyl substituents adjacent to the carbanion centre 

When a fluorine atom is located 3- to a carbanion centre, F—C—C , we would expect the high electronegativity of fluorine to give rise to a very dominant stabUising effect (lo-), since, in this situation, there is no opportunity for Itt repulsion. Indeed, (3-fluorine substituents are very strongly stabilising but the basis of the effect has been a subject of varied interpretation. 

The stereochemical course of hydrogen-deuterium exchange in homochiral PhEtHC CF3 has been studied [15] and, like systems containing other carbanion-stabilising groups, the extent of racemisation of the product varies with solvent. 

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