2. Draw the two possible isomers of C-C-C=C-C-C and name them.
3. Show that 1,2-dichloroethene can exist in two isomeric forms while 1,2-dichloroethane does not.
4. If at either end of a carbon-carbon double bond the two atoms or groups are identical, can the alkene exist as a pair of cis or trans isomers? Write the structures of the cis and trans isomers, if any for the following:
C=C b) C-C=C
f) Cl Cl