The possible stereoisomers from trans-2-butene are
H3C
|
C
|
H
=
H
|
C
|
CH3
→ H−
CH3
|
C
|
Br
−
CH3
|
C
|
Br
−H (I) or H3C−
H
|
C
|
Br
−
H
|
C
|
Br
−CH3 (II) Of these, (II) is a meso compound, that is, one half of the molecule is mirror image of the other half, even though it contains a chiral centre. Thus, there is only one stereoisomer.