SN2 reaction at an asymmetric carbon atom of a dextro alkyl halide always gives a laevo product. This can be explained through the following points:

SN2 Reaction
SN2 (Substitution Nucleophilic Bimolecular) reaction is a type of nucleophilic substitution reaction, in which a nucleophile attacks the electrophilic carbon atom, and the leaving group leaves at the same time. This results in the inversion of the configuration at the stereocenter.

Asymmetric Carbon Atom
An asymmetric carbon atom is a carbon atom that is attached to four different groups or atoms. This carbon atom is also known as a chiral center or stereocenter. The two possible arrangements of the four groups around the asymmetric carbon atom result in a pair of enantiomers.

Dextro Alkyl Halide
A dextro alkyl halide is a molecule that contains an alkyl group and a halogen atom attached to an asymmetric carbon atom. The dextro prefix indicates that the molecule is optically active and rotates plane-polarized light to the right.

Laevo Product
When an SN2 reaction occurs at the asymmetric carbon atom of a dextro alkyl halide, the configuration at the stereocenter is inverted, resulting in the formation of an enantiomer that rotates plane-polarized light to the left. This enantiomer is known as the laevo product.

Racemic Mixture
A racemic mixture is a mixture of equal amounts of two enantiomers. In an SN2 reaction at an asymmetric carbon atom of a dextro alkyl halide, a racemic mixture is not formed because the reaction occurs with inversion of configuration.

Single Optically Active Isomer
Since the SN2 reaction at an asymmetric carbon atom of a dextro alkyl halide results in the formation of a single enantiomer, the product is optically active and rotates plane-polarized light either to the right (dextro) or to the left (laevo).

Dextro Product
A dextro product is formed when a molecule rotates plane-polarized light to the right. In an SN2 reaction at an asymmetric carbon atom of a dextro alkyl halide, a dextro product is not formed because the configuration at the stereocenter is inverted, resulting in the formation of the laevo product.