AL CHEM pastpaper Question (urgent! please help!)

Question

Question from 06' CHem AL pastpaper paper 1

Q 6(c) (i) Mutiple choice

Which of the following compound has a pair of enantiomers?
(I am sorry that I can't draw their structures here)

My question no1: Why the answer is B? How can we determine?
My question no2: How can we name the compound in choice B (IUPAC) ?

Answer 1

Refer to the structure of B below. The carbon atom labelled with a “*” is a chiral carbon atom (or known as asymmetrical carbon atom), because it is attached to 4 different groups or atoms (one -H, one -O, one -C in the ring, one -C in -CH2OH).

圖片參考：http://hk.geocities.com/hoocch2ch2cooh/diagrams/epoxide1.jpg


Due to the presence of a chiral carbon atom, B has two enantiomers as shown below :

圖片參考：http://hk.geocities.com/hoocch2ch2cooh/diagrams/epoxide2.jpg


The IUPAC names of these two enantiomers are D-2,3-epoxypropan-1-ol and L-2,3-expoxypropan-1-ol. Whether it is D- or L- is determined by experiments.