Are the following compounds structural isomers, cis–trans isomers, or enantiomers?
(c) 

Certain omega-3 fatty acids can be found only in animal sources, such as fatty fish. Two of these are eicosapentaenoic acid (EPA) [20:5] and docosahexaenoic acid (DHA) [22:6], both of which are ω-3 fatty acids. DHA has been shown to be important in healthy brain development, so it has recently been added to infant formulas. Breast milk is rich in DHA as long as the mother maintains a healthy diet that includes fish. Draw skeletal structures of the fatty acids EPA and DHA.

Mark the chiral centers in the following molecules, if any, with an asterisk (*).

(d)

Draw the enantiomer of each of the following compounds. If the compound is not chiral, state that fact.

(c)

For each pair of molecules, identify the pair as:

A. structural isomers.

B. the same molecule (conformational isomers).

C. cis–trans stereoisomers.

D. different molecules.                                                                                                                                                                 

(b)

Mark the chiral centers in the following molecules, if any, with an asterisk (*).

(a)

Mark the chiral centers in the following molecules, if any, with an asterisk (*).

(d)