The aliphatic compounds are, for example, compounds of the formula X--CH2 --Y, wherein X represents an electrophilic group and Y represents an inert, i.e. inactive, organic group, for example an alkyl group or a phenyl group which is unsubstituted or substituted by alkyl or alkoxy of 1 to 4 carbon atoms or also represents an electrophilic group; the electrophilic groups represented by X and Y can