Electrophilic addition creating a chiral center

Steps:

• Trichloroethene structure: ClHC=CCl₂, an alkene with unsymmetrical double bond.
• Br₂ undergoes electrophilic addition, forming bromonium ion intermediate; Br⁻ attacks, yielding anti addition product ClHBrC-CBrCl₂.
• The carbon originally CHCl gains Br, becoming CHClBr attached to CBrCl₂, H, Cl, Br—four different groups, creating a chiral center.
• Other reagents lead to achiral products via substitution or non-stereogenic addition.

Why A is correct:

• Bromine addition to the alkene follows anti-Markovnikov-like stereospecificity, producing a molecule with a stereogenic carbon (chiral center) per the definition of chirality (non-superimposable mirror images).

Why the others are wrong:

• B. HCl adds Markovnikov to give ClH₂C-CCl₃, with no chiral center (symmetric carbons).
• C. NaCN performs nucleophilic substitution, yielding Cl₂HC-CH(CN)Cl, but product lacks four different substituents on any carbon.
• D. NaOH causes dehydrohalogenation or hydrolysis, producing achiral dichloroethene or carboxylic acid derivatives.

Final answer: A