Chapter 15, Problem 15.30P

(a)

Interpretation Introduction

Interpretation:

The compound 1-pentene exhibit geometric isomerism or not has to be given and two isomers has to be drawn and named for the given structure.

Concept Introduction:

The structure of the compound is given by its systematic name.

To give the structure from the name of the compound, the root name has to be identified.  The root name indicates the number of carbon atoms present in the longest chain.

Then the functional group (suffix) has to be identified.  It indicates whether any functional groups are present in the compound, it also gives whether the compound is an alkane or alkene or alkyne.

The prefix of the name indicates the branched groups and their positions on the carbon chain.

The name of the compound is in the form

Prefix + Root + Suffix

The geometric isomers are said to be the isomers which shows different orientation of groups around a double bond.  The geometric isomers are also known as cis-trans isomers.

When two similar or higher priority groups are attached to the carbon on same side, it is said to be cis-isomer.

When two similar or higher priority groups are attached to the carbon on opposite sides, it is said to be trans-isomer.

To exhibit the geometric isomerism, a molecule should have double bonded carbon atoms ($\text{C=C}$) and each double bonded carbon should be bonded to two different groups.

Explanation of Solution

The given compound is 1-pentene.

The pentene contains five carbon atoms in chain. As the suffix is –ene, it belongs to alkene group and contains a double bond.  The position of the double bond in 1-pentene is in between first and second carbon atoms.  The structure of 1-pentene is given as

The given compound is 1-pentene.  The given compound contains a double bond and each carbon in the double bond is bonded to two groups.

The geometric isomers are cis-isomer and trans-isomer.  In cis-isomer, similar groups are attached to the carbon on same side and in trans-isomer, similar groups are attached to the carbon on opposite sides.

As 1-pentene contains two similar groups ($\text{-H}$) on one of the double bonded carbon atom, it does not exhibit geometric isomerism.

(b)

Interpretation Introduction

Interpretation:

The compound 2-pentene exhibit geometric isomerism or not has to be given and two isomers has to be drawn and named for the given structure.

Concept Introduction:

The structure of the compound is given by its systematic name.

To give the structure from the name of the compound, the root name has to be identified.  The root name indicates the number of carbon atoms present in the longest chain.

Then the functional group (suffix) has to be identified.  It indicates whether any functional groups are present in the compound, it also gives whether the compound is an alkane or alkene or alkyne.

The prefix of the name indicates the branched groups and their positions on the carbon chain.

The name of the compound is in the form

Prefix + Root + Suffix

The geometric isomers are said to be the isomers which shows different orientation of groups around a double bond.  The geometric isomers are also known as cis-trans isomers.

When two similar or higher priority groups are attached to the carbon on same side, it is said to be cis-isomer.

When two similar or higher priority groups are attached to the carbon on opposite sides, it is said to be trans-isomer.

To exhibit the geometric isomerism, a molecule should have double bonded carbon atoms ($\text{C=C}$) and each double bonded carbon should be bonded to two different groups.

Explanation of Solution

The given compound is 2-pentene.

The pentene contains five carbon atoms in chain. As the suffix is –ene, it belongs to alkene group and contains a double bond.  The position of the double bond in 2-pentene is in between second and third carbon atoms.  The structure of 2-pentene is given as

The given compound is 2-pentene.  The given compound contains a double bond and each carbon in the double bond is bonded to two different groups.  Hence, the given compound exhibits geometric isomerism.

The geometric isomers are cis-isomer and trans-isomer.  In cis-isomer, similar or higher priority groups are attached to the carbon on same side and in trans-isomer, similar or higher priority groups are attached to the carbon on opposite sides.

The groups present on either sides of the double bond are given as higher priority groups (${\text{-CH}}_{\text{2}}{\text{CH}}_{\text{3}}{\text{ and -CH}}_{\text{3}}$) and lower priority groups ($\text{-H }$).  The isomers formed from the given compound are

(c)

Interpretation Introduction

Interpretation:

The compound 1-chloropropene exhibit geometric isomerism or not has to be given and two isomers has to be drawn and named for the given structure.

Concept Introduction:

The structure of the compound is given by its systematic name.

To give the structure from the name of the compound, the root name has to be identified.  The root name indicates the number of carbon atoms present in the longest chain.

Then the functional group (suffix) has to be identified.  It indicates whether any functional groups are present in the compound, it also gives whether the compound is an alkane or alkene or alkyne.

The prefix of the name indicates the branched groups and their positions on the carbon chain.

The name of the compound is in the form

Prefix + Root + Suffix

The geometric isomers are said to be the isomers which shows different orientation of groups around a double bond.  The geometric isomers are also known as cis-trans isomers.

When two similar or higher priority groups are attached to the carbon on same side, it is said to be cis-isomer.

When two similar or higher priority groups are attached to the carbon on opposite sides, it is said to be trans-isomer.

To exhibit the geometric isomerism, a molecule should have double bonded carbon atoms ($\text{C=C}$) and each double bonded carbon should be bonded to two different groups.

Explanation of Solution

The given compound is 1-chloropropene.

The propene contains three carbon atoms in chain. As the suffix is –ene, it belongs to alkene group and contains a double bond.  The position of the double bond in 1-chloropropene is in between first and second carbon atoms.  One chloro group ($\text{-Cl}$ ) is attached to the first carbon atom of the propene molecule.  The structure of 1-chloropropene is given as

The given compound is 1-chloropropene.  The given compound contains a double bond and each carbon in the double bond is bonded to two different groups.  Hence, the given compound exhibits geometric isomerism.

The geometric isomers are cis-isomer and trans-isomer.  In cis-isomer, similar or higher priority groups are attached to the carbon on same side and in trans-isomer, similar or higher priority groups are attached to the carbon on opposite sides.

The groups present on either sides of the double bond are given as higher priority groups (${\text{-Cl and -CH}}_3$) and lower priority groups ($\text{-H }$).  The isomers formed from the given compound are

(d)

Interpretation Introduction

Interpretation:

The compound 2-chloropropene exhibit geometric isomerism or not has to be given and two isomers has to be drawn and named for the given structure.

Concept Introduction:

The structure of the compound is given by its systematic name.

To give the structure from the name of the compound, the root name has to be identified.  The root name indicates the number of carbon atoms present in the longest chain.

Then the functional group (suffix) has to be identified.  It indicates whether any functional groups are present in the compound, it also gives whether the compound is an alkane or alkene or alkyne.

The prefix of the name indicates the branched groups and their positions on the carbon chain.

The name of the compound is in the form

Prefix + Root + Suffix

The geometric isomers are said to be the isomers which shows different orientation of groups around a double bond.  The geometric isomers are also known as cis-trans isomers.

When two similar or higher priority groups are attached to the carbon on same side, it is said to be cis-isomer.

When two similar or higher priority groups are attached to the carbon on opposite sides, it is said to be trans-isomer.

To exhibit the geometric isomerism, a molecule should have double bonded carbon atoms ($\text{C=C}$) and each double bonded carbon should be bonded to two different groups.

Explanation of Solution

The given compound is 2-chloropropene.

The propene contains three carbon atoms in chain. As the suffix is –ene, it belongs to alkene group and contains a double bond.  The position of the double bond in 2-chloropropene is in between first and second carbon atoms.  One chloro group ($\text{-Cl}$ ) is attached to the second carbon atom of the propene molecule.  The structure of 2-chloropropene is given as

The given compound is 2-chloropropene.  The given compound contains a double bond and each carbon in the double bond is bonded to two groups.

The geometric isomers are cis-isomer and trans-isomer.  In cis-isomer, similar groups are attached to the carbon on same side and in trans-isomer, similar groups are attached to the carbon on opposite sides.

As 2-chloropropene contains two similar groups ($\text{-H}$) on one of the double bonded carbon atom, it does not exhibit geometric isomerism.