chem高手請入

CH3CH=CHCH(CH3)CH2CH3

First, the alkyl groups attached C=C bond are not symmetrical, so there'd E/Z isomerism.
Second, the 4th carbon counted from the left has 4 different groups of atoms attached to it, so there'd be stereoisomerism.

thus, there're 2x2 = 4 isomers.


圖片參考：http://imgcld.yimg.com/8/n/HA00075708/o/20131128173414.jpg

The two on the top are the E/Z isomers of the two at the bottom, respectively;
the two on the left are the stereoisomers of the two on the right, respectively.

4R-2-cis-CH3C(H)=C(H)-C*(H)(CH3)(CH2CH3);

4S-2-cis-CH3C(H)=C(H)-C*(H)(CH3)(CH2CH3);

4R-2-trans-CH3C(H)=C(H)-C*(H)(CH3)(CH2CH3);

4S-2-trans-CH3C(H)=C(H)-C*(H)(CH3)(CH2CH3)


The first and the second are the E/Z (or CIS/TRANS) ISOMERS of the third and the forth, respectively;
the first and the third are the ENANTIOMERS of the second and the forth, respectively.