Acetone weakly hydrogen-bonds with chloroform.The hydrogen on an electronegative atom has electron density that is getting pulled on by an electronegative atom nearby. A particularly electropositive hydrogen atom has electron density that is getting pulled on by an electronegative atom nearby
When acetone and choloroform are reacted it form as a product of the following reaction
CH3-CO-CH3 + CHCl3--------> (CH3)2 -- COH(CCl3)
The anions of the reactant CH3CO and CCl3 form bonds with cations H+ and CH3+ respectively, as a result forming chloretone.