Chapter 11, Problem 26P

Write structural formulas for each of the following:

$\text{3,4-Octadiene}$

$\text{(}E,E\text{)-3,5-Octadiene}$

$\text{(}Z,Z\text{)-1,3-Cyclooctadiene}$

$\text{(}Z,Z\text{)-1,4-Cyclooctadiene}$

$\text{(}E,E\text{)-1,5-Cyclooctadiene}$

$\text{5-Allyl-1,3-cyclopentadiene}$ $\text{(}2E,4Z,6E\text{)-2,4,6-Octatriene}$

$trans\text{-1,2-Divinylcyclopropane}$

$\text{2,4-Dimethyl-1,3-pentadiene}$

Interpretation Introduction

Interpretation:

The structural formula of the given compounds is to be written.

Concept introduction:

When writing the structural formula of any compound, first the functional group from the suffix of the given name is identified.

The longest carbon chain containing the functional group is located.

The carbon atoms of the chain are numbered in a way that the functional group is at lowest numbered carbon atom.

Substituents are attached to the parent chain according to their positions given in the name.

In alkenes, the Z isomers have the higher ranked substituents on the same side of the double bond, and in E isomers, higher ranked substituents are on the opposite sides of the double bond.

Answer to Problem 26P

Solution:

a)

b)

c)

d)

e)

f)

g)

h)

i)

Explanation of Solution

a) The given compound is $3,4-$ octadiene.

The parent name contains the word “$\text{octa}$” in it, which means that the longest carbon chain contains eight carbon atoms. The suffix added to $\text{octa}$ is $\text{-diene}$, which means that there are two double bonds present in the parent chain. The numbers $3$ and $4$ indicate the positions of the double bonds in the parent chain.

The structural formula is as follows:

b) The given compound is $\left(E,E\right)-3,5-$ octadiene.

The parent name contains the word “$\text{octa}$” in it, which means that the longest carbon chain contains eight carbon atoms. The suffix added to $\text{octa}$ is $\text{-diene}$, which means that there are two double bonds present in the parent chain. The numbers $3$ and $5$ indicate the positions of the double bonds in the parent chain. Both the double bonds have E configuration. The higher priority groups must be on the opposite sides of the double bond.

The structural formula is as follows:

c) The given compound is $\left(Z,Z\right)-1,3-$ cyclooctadiene.

The parent name contains the word “cycloocta” in it, which means that the parent carbon chain contains eight carbon atoms in a cyclic form. The suffix added is $\text{-diene}$, which means that there are two double bonds present in the parent chain. The numbers $1$ and $3$ indicate the positions of the double bonds in the parent chain. Both the double bonds have Z configuration. The higher priority groups must be on the same sides of the double bond.

The structural formula is as follows:

d) The given compound is $\left(Z,Z\right)-1,4-$ cyclooctadiene.

The parent name contains the word “cycloocta” in it, which means that the parent carbon chain contains eight carbon atoms in a cyclic form. The suffix added is $\text{-diene}$, which means that there are two double bonds present in the parent chain. The numbers $1$ and $4$ indicate the positions of the double bonds in the parent chain. Both the double bonds have Z configuration. The higher priority groups must be on the same sides of the double bond.

The structural formula is as follows:

e) The given compound is $\left(E,E\right)-1,5-$ cyclooctadiene.

The parent name contains the word “cycloocta” in it, which means that the parent carbon chain contains eight carbon atoms in a cyclic form. The suffix added is $\text{-diene}$, which means that there are two double bonds present in the parent chain. The numbers $1$ and $5$ indicate the positions of the double bonds in the parent chain. Both the double bonds have E configuration. The higher priority groups must be on the opposite sides of the double bond.

The structural formula is as follows:

f) The given compound is $\left(Z,Z\right)-1,4-$ octatriene.

The parent name contains the word “$\text{octa}$” in it, which means that the longest carbon chain contains eight carbon atoms. The suffix added to $\text{octa}$ is $\text{-triene}$, which means that there are three double bonds present in the parent chain. The numbers $\text{2, 4, 6}$ indicate the positions of the double bonds in the parent chain. The double bonds between $\text{C2-C3}$ and between $\text{C6-C7}$ have E configuration. The double bond between $\text{C4-C5}$ has Z configuration.

The structural formula is as follows:

g) The given compound is $5-\text{allyl}-1,3-\text{cyclopentadiene}$.

The parent name contains the word “cyclopenta” in it, which means that the parent carbon chain contains five carbon atoms in a cyclic form. The suffix added is $\text{-diene}$, which means that there are two double bonds present in the parent chain. The numbers $1$ and $3$ indicate the positions of the double bonds in the parent chain. There is an allyl group attached to the $\text{C5}$ carbon atom.

The structural formula is as follows:

h) The given compound is $\text{trans}-1,2-\text{divinylcyclopropane}$.

The parent name contains the word cyclopropane in it, which means that the parent carbon chain contains three carbon atoms in a cyclic form. There are two vinyl groups attached to the cyclopropane. The numbers $1$ and $2$ indicate the positions of the vinyl groups on the parent chain. These two vinyl groups are trans to each other.

The structural formula is as follows:

i) The given compound is $2,4-\text{dimethyl}-1,3-\text{pentadiene}$.

The parent name contains the word “penta” in it, which means that the longest carbon chain contains five carbon atoms. The suffix added is $\text{-diene}$, which means that there are two double bonds present in the parent chain. The numbers $\text{1 and 3}$ indicate the positions of the double bonds in the parent chain. One methyl group is attached to $\text{C2}$ while another methyl group is attached to $\text{C4}$ carbon atom.

The structural formula is as follows: