Orgo chem help with stereoisomers!!?

Question

Among the compounds represented by the constitution 2-bromo-1,3-pentadiene,

a. there are a total of 2 stereoisomers and both are optically active.

b. there are a total of 2 stereoisomers and neither is optically active.

c. there are a total of 4 stereoisomers; two are optically active and two are not.

d. there are a total of 4 stereoisomers and all are optically active.

e. there are a total of 4 stereoisomers and none is optically active.

Answer 1

First draw the structure named.  Are there any chirality centers?  This requires a carbon to make a single bond to each of 4 DIFFERENT things.  If so, each chirality center can be either R or S resulting in two optically active stereoisomers.  Are there any double bonds?  If so, can they have E/Z (or cis/trans) forms.  For two forms to exist around a double bond, the two things attached to each end of that C=C must be different from each other. For example,  C=C that has a C and an H on each of the C=C carbons can have E and Z forms.  However, if it has 2 H's on one end and a C and a Cl on the other, the 2 H's are identical and no E/Z forms are possible.  Each double bond having E and Z forms can give 2 stereoisomers, but they are (almost) always achiral so are not optically active.