Write the structures of the following compounds.
`a.` `3,7-` Dimethylocta`-1,3,6-` triene
`b.` `4-`Allyl`-3-` propenyl`-1,3-` cyclohexadiene
`c.` `2-` Ethenyl bicyclo `[4.40]-1,5,8-` decatriene
`d.` Bicyclo `[2.2.1]-2,5-` heptadiene

Explanation

Step I: First, draw a chain and eight `C` atoms. Then number it from any side.

Step `II:` Put the substituent at the mentioned positions.

or

b. Step I: Write the group.

Step II: Write the structure of the cyclohexane and number it rom any side . Then, put the substituent at the mentioned position.

It can be named in `IUPAC` nomenclature as 3-( prop -1-enyl)-4-2-enyl)-1,3- cyclohexadiene.
c. Step I: For bicyclo compunds, first put the number of `C` atomes written in the bracket around the joining point.

Two joining points joined together when there is zero `C` atom at the third number in the bracket.
Step `II:` Number the `C` atom from the bridge `-` head and move from the larger ring to a smaller ring (here both are the same).

Step `III:` Put the substituent at the mentioned positions.

d. Step I: As mentioned above in `3 (c)`, first put the first two numbers of the `C` atom written in the bracket.

Only two points not joined together when there is `1-C` at the third number in the bracket
Step II: Now put the third number of `C` atom written in the bracket and join it from the bridge - head (joining point).

Step III: Number the `C` atom from the bridge - head and put the substituent at the mentioned position.