Chapter 12, Problem 12.21P

Interpretation Introduction

(a)

Interpretation:

The given statement is true or false should be determined.

The IUPAC name of an alkene is derived from the name of the longest carbon chain that contains the carbon-carbon double bond.

Concept Introduction:

The IUPAC name is the set of rules that is created and applied by the International Union of pure and Applied Chemistry to generate systematic proper name of chemical compounds. This nomenclature is used to describe and identify the type and position of functional groups, side chains, double or triple bonds etc. in alphabetical order to provide systematic name to compound.

Alkenes are the compounds with very weak London dispersion forces and are nonpolar. They contain same skeleton structure and physical properties like alkanes but liquid at room temperature.

Cis-trans stereoisomerisms are seen in alkenes compounds. Due to presence of two different groups bonded to carbon of carbon-carbon double bond, restricted action occurs in it and results into cis-trans isomerism. If same groups are present on the same side, then the isomer is called as cis-isomer and the same groups are present on different side the isomer is called as trans-isomer.

Answer to Problem 12.21P

The given statement is true.

Explanation of Solution

As per general rules of IUPAC nomenclature rules, first to find out the longest carbon chain which contains double bond and prefix is given after the parent chain’s length that tells about the carbon atoms number in it with suffix of −ene. For example, longest parent chain with four carbons is named started as Butene. Therefore, the given statement is true.

Interpretation Introduction

(b)

Interpretation:

The given statement is true or false should be determined.

The IUPAC name of ${\text{CH}}_{\text{3}}{\text{-CH=CH-CH}}_{\text{3}}$ is 1,2-dimethylethene.

Concept Introduction:

The IUPAC name is the set of rules that is created and applied by the International Union of pure and Applied Chemistry to generate systematic proper name of chemical compounds. This nomenclature is used to describe and identify the type and position of functional groups, side chains, double or triple bonds etc. in alphabetical order to provide systematic name to compound.

Alkenes are the compounds with very weak London dispersion forces and are nonpolar. They contain same skeleton structure and physical properties like alkanes but liquid at room temperature.

Cis-trans stereoisomerisms are seen in alkenes compounds. Due to presence of two different groups bonded to carbon of carbon-carbon double bond, restricted action occurs in it and results into cis-trans isomerism.

If same groups are present on the same side, then the isomer is called as cis- isomer and the same groups are present on different side the isomer is called as trans- isomer.

Answer to Problem 12.21P

The given statement is false.

Explanation of Solution

IUPAC name of ${\text{CH}}_{\text{3}}{\text{-CH=CH-CH}}_{\text{3}}$ is 2-butene because of parent chain contains four carbons atoms and double bond is present in between second and third carbon atoms.

Therefore, the given statement is false.

Interpretation Introduction

(c)

Interpretation:

The given statement is true or false should be determined.

2-Methyl-2-butene shows cis-trans isomerism.

Concept Introduction:

The IUPAC name is the set of rules that is created and applied by the International Union of pure and Applied Chemistry to generate systematic proper name of chemical compounds. This nomenclature is used to describe and identify the type and position of functional groups, side chains, double or triple bonds etc. in alphabetical order to provide systematic name to compound.

Alkenes are the compounds with very weak London dispersion forces and are nonpolar. They contain same skeleton structure and physical properties like alkanes but liquid at room temperature.

Cis-trans stereoisomerisms are seen in alkenes compounds. Due to presence of two different groups bonded to carbon of carbon-carbon double bond, restricted action occurs in it and results into cis-trans isomerism.

If same groups are present on the same side, then the isomer is called as cis- isomer and the same groups are present on different side the isomer is called as trans- isomer.

Answer to Problem 12.21P

The given statement is false.

Explanation of Solution

2-Methyl-2-butene contains two methyl groups present on carbon atom of carbon-carbon double bond other carbon contains also methyl group.

To get cis and trans isomers, two different groups should be present on the carbon atoms of the carbons with double bond.

Thus, the statement is false.

Interpretation Introduction

(d)

Interpretation:

The given statement is true or false should be determined.

1,2-dimethylcyclohexene shows cis-trans isomerism.

Concept Introduction:

The IUPAC name is the set of rules that is created and applied by the International Union of pure and Applied Chemistry to generate systematic proper name of chemical compounds. This nomenclature is used to describe and identify the type and position of functional groups, side chains, double or triple bonds etc. in alphabetical order to provide systematic name to compound.

Alkenes are the compounds with very weak London dispersion forces and are nonpolar. They contain same skeleton structure and physical properties like alkanes but liquid at room temperature.

Cis-trans stereoisomerisms are seen in alkenes compounds. Due to presence of two different groups bonded to carbon of carbon-carbon double bond, restricted action occurs in it and results into cis-trans isomerism.

If same groups are present on the same side then the isomer is called as cis- isomer and the same groups are present on different side the isomer is called as trans- isomer.

Answer to Problem 12.21P

The given statement is false.

Explanation of Solution

Following are the structures of the isomers of 1,2-dimethylcyclohexane. Form this, we can see that all four atoms of carbon-carbon double bond are lying in same plane.

Therefore, the given statement is false.

Interpretation Introduction

(e)

Interpretation:

The given statement is true or false should be determined.

The IUPAC name of ${\text{CH}}_{\text{2}}{\text{=CHCH=CHCH}}_{\text{3}}$ is 1,3-pentadiene.

Concept Introduction:

The IUPAC name is the set of rules that is created and applied by the International Union of pure and Applied Chemistry to generate systematic proper name of chemical compounds. This nomenclature is used to describe and identify the type and position of functional groups, side chains, double or triple bonds etc. in alphabetical order to provide systematic name to compound.

Alkenes are the compounds with very weak London dispersion forces and are nonpolar. They contain same skeleton structure and physical properties like alkanes but liquid at room temperature.

Cis-trans stereoisomerisms are seen in alkenes compounds. Due to presence of two different groups bonded to carbon of carbon-carbon double bond, restricted action occurs in it and results into cis-trans isomerism.

If same groups are present on the same side then the isomer is called as cis- isomer and the same groups are present on different side the isomer is called as trans- isomer.

Answer to Problem 12.21P

The given statement is true.

Explanation of Solution

The IUPAC name of ${\text{CH}}_{\text{2}}{\text{=CHCH=CHCH}}_{\text{3}}$ is 1,3-pentadiene. This because of presence of double bonds in between first and second as well as in between third and fourth carbon atoms and the parent chain contain total five carbon atoms. Therefore, the given statement is true.

Interpretation Introduction

(f)

Interpretation:

The given statement is true or false should be determined.

1,3-Butadiene has two carbon-carbon double bonds and 2² =4 stereoisomers are possible for it.

Concept Introduction:

The IUPAC name is the set of rules that is created and applied by the International Union of pure and Applied Chemistry to generate systematic proper name of chemical compounds. This nomenclature is used to describe and identify the type and position of functional groups, side chains, double or triple bonds etc. in alphabetical order to provide systematic name to compound.

Alkenes are the compounds with very weak London dispersion forces and are nonpolar. They contain same skeleton structure and physical properties like alkanes but liquid at room temperature.

Cis-trans stereoisomerisms are seen in alkenes compounds. Due to presence of two different groups bonded to carbon of carbon-carbon double bond, restricted action occurs in it and results into cis-trans isomerism.

If same groups are present on the same side, then the isomer is called as cis- isomer and the same groups are present on different side the isomer is called as trans- isomer.

Answer to Problem 12.21P

The given statement is false.

Explanation of Solution

Following is the structure of 1,3-Butadiene. There are no stereocenters are present in the structure of 1,3-Butadiene. There should be presence of different groups for isomerism.

Therefore, the given statement is false.