Chapter 7, Problem 31P

Write structural formulas for each of the following:

$\text{1-Heptene}$

$\text{3-Ethyl-2-pentene}$

$\text{cis-3-Octene}$

$\text{trans-1,4-Dichloro-2-butene}$

$\text{(Z)-3-Methyl-2-hexene}$

$\text{(E)-3-Chloro-2-hexene}$

$\text{1-Bromo-3-methylcyclohexene}$

$\text{1-Bromo-6-methylcyclohexene}$

$\text{4-Methyl-4-penten-2-ol}$

Vinylcycloheptane

$\text{1,1-Diallylcyclopropane}$

$\text{trans-1-Isopropenyl-3-methylcyclohexane}$

Interpretation Introduction

Interpretation:

The structural formula for each 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 such way that the functional group is at the 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 opposite sides of the double bond.

Answer to Problem 31P

Solution:

Explanation of Solution

a) $\text{1-Heptene}$

The parent chain has seven carbon atoms since the name has the word “hept.” The functional group is alkene. The double bond is present between $\text{C1 and C2}$ carbon atoms.

The structural formula is as follows:

b) $\text{3-Ethyl-2-pentene}$

The parent chain has five carbon atoms since the name has the word “pent.” The functional group is alkene. The double bond is present between $\text{C2 and C3}$ carbon atoms. An ethyl group is attached to the $\text{C3}$ carbon atom of the pentene chain.

The structural formula is as follows:

c) $\text{cis-3-Octene}$

The parent chain has eight carbon atoms since the name has the word “oct.” The functional group is alkene. The double bond is present between $\text{C3 and C4}$ carbon atoms. The similar substituents attached to the double bonded carbon atoms must be on the same side of the double bond since the conformation is cis.

The structural formula is as follows:

d) $\text{trans-1,4-Dichloro-2-butene}$

The parent chain has four carbon atoms since the name has the word “but.” The functional group is alkene. The double bond is present between $\text{C2 and C3}$ carbon atoms. One chlorine atom is attached to the $\text{C1 and C4}$ carbon atoms each. The similar substituents attached to the double bonded carbon atoms must be on the opposite side of the double bond since the conformation is trans.

The structural formula is as follows:

e) $\left(\text{Z}\right)\text{-3-Methyl-2-hexene}$

The parent chain has six carbon atoms since the name has the word “hex.” The functional group is alkene. The double bond is present between $\text{C2 and C3}$ carbon atoms. A methyl group is attached to the $\text{C3}$ carbon atom of the hexene chain.

The higher ranked substituents attached to the double bonded carbon atoms must be on the same side of the double bond since the conformation is Z. The structural formula is as follows:

f) $\left(\text{E}\right)\text{-3-Chloro-2-hexene}$

The parent chain has six carbon atoms since the name has the word “hex.” The functional group is alkene. The double bond is present between $\text{C2 and C3}$ carbon atoms. A chlorine atom is attached to the $\text{C3}$ carbon atom of the hexene chain.

The higher ranked substituents attached to the double bonded carbon atoms must be on the opposite side of the double bond since the conformation is E.

The structural formula is as follows:

g) $\text{1-Bromo-3-methylcyclohexene}$

The parent is a six carbon atom ring since the name has the word “cyclohex.” The functional group is alkene. The double bond is present between $\text{C1 and C2}$ carbon atoms. A bromine atom is attached to the $\text{C1}$ carbon atom of the cyclohexene ring while a methyl group is attached to the $\text{C3}$ carbon atom.

The structural formula is as follows:

h) $\text{1-Bromo-6-methylcyclohexene}$

The parent is a six carbon atom ring since the name has the word “cyclohex.” The functional group is alkene. The double bond is present between $\text{C1 and C2}$ carbon atoms. A bromine atom is attached to the $\text{C1}$ carbon atom of the cyclohexene ring while a methyl group is attached to the $\text{C6}$ carbon atom.

The structural formula is as follows:

i) $\text{4-Methyl-4-penten-2-ol}$

The parent chain has five carbon atoms since the name has the word “pent.” A double bond is present between $\text{C4 and C5}$ carbon atoms. A hydroxyl group is attached to the $\text{C2}$ carbon atom while a methyl group is attached to the $\text{C4}$ carbon atom of the pentane chain.

The structural formula is as follows:

j) Vinylcycloheptane

The structure of a vinyl group is ${\text{CH}}_{\text{2}}\text{= CH-}$

A cycloheptane ring is attached to this vinyl group. The ring has seven carbon atoms. The structural formula is as follows:

k) $\text{1,1-Diallylcyclopropane}$

$\text{1,1-Diallylcyclopropane}$ denotes that two allyl groups. i.e.. $-C{H}_2-CH=C{H}_2$, are attached to the $C-1$ carbon atom of cyclopropane. So the structural formula of $\text{1,1-Diallylcyclopropane}$ is as follows:

l) $\text{Trans-1-Isopropenyl-3-methylcyclohexane}$

The parent is a six carbon atom ring since the name has the word “cyclohex.” An isopropenyl group is attached to the $\text{C1}$ carbon atom of the cyclohexene ring while a methyl group is attached to the $\text{C3}$ carbon atom. The two substituents must be on the opposite sides of the ring since the conformation is trans.

The structural formula is as follows: