| 41. | Two mirror images of a chiral molecule are called enantiomers or optical isomers.
 
  | 
 | 42. | Unlike its enantiomer, BD1031, BD1018 acts as a sigma receptor antagonist.
 
  | 
 | 43. | It exists as two enantiomers and can be obtained as a racemic mixture.
 
  | 
 | 44. | If " all " the stereocenters are opposite, they are enantiomers.
 
  | 
 | 45. | Thus, the two enantiomers of the reactant produce a single enantiomer of product.
 
  | 
 | 46. | Thus, the two enantiomers of the reactant produce a single enantiomer of product.
 
  | 
 | 47. | It is the active dextrorotatory enantiomer of methylphenidate.
 
  | 
 | 48. | In nature, it occurs in both the L-and D-enantiomers.
 
  | 
 | 49. | A non-racemic mixture of two enantiomers will have a net optical rotation.
 
  | 
 | 50. | It is the " R "-enantiomer of the cetirizine racemate.
 
  |