Chapter 12, Problem 12.108EP

(a)

Interpretation Introduction

Interpretation:

The molecular formula for the given hydrocarbon has to be found.

Concept Introduction:

Organic compounds are the important basis of life.  They include gasoline, coal, dyes, and clothing fibers etc.  The compounds that are obtained from living organisms are termed as organic compounds and those obtained from the earth are known as inorganic compounds.  Organic compounds are found in earth also apart from living organisms.  All the organic compounds contain the element carbon.  Urea was synthesized in the laboratory which is an organic compound.

Hydrocarbons are the organic compounds that contain only hydrogen and carbon atoms.  Hydrocarbon derivatives are the one in which the compounds contain hydrogen and carbon atoms along with one or more additional elements.  The additional elements that can be present in hydrocarbon derivatives are oxygen, nitrogen, sulphur, chlorine, bromine etc.

Hydrocarbons are further classified into two categories.  They are saturated hydrocarbons and unsaturated hydrocarbons.  The hydrocarbons that contain single bonds between carbon atoms in the entire molecule is known as saturated hydrocarbon.  The hydrocarbons that contain atleast one double or triple bond between two carbon atoms in the entire molecule is known as unsaturated hydrocarbon.

Cycloalkanes are a class of saturated hydrocarbons that contain a ring of carbon atoms with or without alkyl substituents on it.  The general molecular formula for cycloalkanes is ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n}}$.  “n” is the number of carbon atoms present.  Some of the basic examples of cycloalkanes are cyclopropane (${\text{C}}_{\text{3}}{\text{H}}_{\text{6}}$), cyclobutane (${\text{C}}_{\text{4}}{\text{H}}_8$).

In a line-angle structural formula of cycloalkanes, the intersection of two lines represent a methylene group (${\text{CH}}_{\text{2}}$ group).  When substituents are present in the cycloalkane ring, three- and four-way intersections of lines are also possible.  $\text{CH}$ group is present when there is a three-way intersection and a carbon atom alone is present when there is a four-way intersection.

Answer to Problem 12.108EP

The molecular formula for the given hydrocarbon is ${\text{C}}_{\text{7}}{\text{H}}_{\text{14}}$.

Explanation of Solution

Given name of cycloalkane is 1,2-dimethylcyclopentane.  From the name it is understood that the parent cycloalkane is five carbon cyclic ring which is cyclopentane.  The substituents present on the cyclopentane ring are two methyl groups, each at first and second carbon.  Therefore, the line-angle structural formula for 1,2-dimethylcyclopentane can be drawn as shown below,

The above structure is a line-angle structural formula representation.  This structure has a total of five intersections and two end lines.  Therefore, the total number of carbon atoms present in the given structure is found to be seven.

The molecular formula for the given cycloalkane can be found using the general molecular formula.  General molecular formula for cycloalkane is ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n}}$.  The total number of carbon atoms in the given cycloalkane is 7.  This means “n” is seven.  Substitution this is the general molecular formula as shown below, the molecular formula can be obtained.

  $\begin{array}{l}{\text{C}}_{\text{n}}{\text{H}}_{\text{2n}}\\ {\text{C}}_{\text{7}}{\text{H}}_{\text{(2*7)}}\\ {\text{C}}_{\text{7}}{\text{H}}_{\text{14}}\end{array}$

The molecular formula for the given hydrocarbon is found to be ${\text{C}}_{\text{7}}{\text{H}}_{\text{14}}$.

Conclusion

The molecular formula for the given hydrocarbon is found as ${\text{C}}_{\text{7}}{\text{H}}_{\text{14}}$.

(b)

Interpretation Introduction

Interpretation:

The molecular formula for the given hydrocarbon has to be found.

Concept Introduction:

Organic compounds are the important basis of life.  They include gasoline, coal, dyes, and clothing fibers etc.  The compounds that are obtained from living organisms are termed as organic compounds and those obtained from the earth are known as inorganic compounds.  Organic compounds are found in earth also apart from living organisms.  All the organic compounds contain the element carbon.  Urea was synthesized in the laboratory which is an organic compound.

Hydrocarbons are the organic compounds that contain only hydrogen and carbon atoms.  Hydrocarbon derivatives are the one in which the compounds contain hydrogen and carbon atoms along with one or more additional elements.  The additional elements that can be present in hydrocarbon derivatives are oxygen, nitrogen, sulphur, chlorine, bromine etc.

Hydrocarbons are further classified into two categories.  They are saturated hydrocarbons and unsaturated hydrocarbons.  The hydrocarbons that contain single bonds between carbon atoms in the entire molecule is known as saturated hydrocarbon.  The hydrocarbons that contain atleast one double or triple bond between two carbon atoms in the entire molecule is known as unsaturated hydrocarbon.

Cycloalkanes are a class of saturated hydrocarbons that contain a ring of carbon atoms with or without alkyl substituents on it.  The general molecular formula for cycloalkanes is ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n}}$.  “n” is the number of carbon atoms present.  Some of the basic examples of cycloalkanes are cyclopropane (${\text{C}}_{\text{3}}{\text{H}}_{\text{6}}$), cyclobutane (${\text{C}}_{\text{4}}{\text{H}}_8$).

In a line-angle structural formula of cycloalkanes, the intersection of two lines represent a methylene group (${\text{CH}}_{\text{2}}$ group).  When substituents are present in the cycloalkane ring, three- and four-way intersections of lines are also possible.  $\text{CH}$ group is present when there is a three-way intersection and a carbon atom alone is present when there is a four-way intersection.

Answer to Problem 12.108EP

The molecular formula for the given hydrocarbon is ${\text{C}}_{\text{7}}{\text{H}}_{\text{14}}$.

Explanation of Solution

Given name of cycloalkane is 1,3-dimethylcyclopentane.  From the name it is understood that the parent cycloalkane is five carbon cyclic ring which is cyclopentane.  The substituent present on the cyclopentane ring are two methyl groups, each at first and third carbon.  Therefore, the line-angle structural formula for 1,3-dimethylcyclopentane can be drawn as shown below,

The above structure is a line-angle structural formula representation.  This structure has a total of five intersections and two end lines.  Therefore, the total number of carbon atoms present in the given structure is found to be seven.

The molecular formula for the given cycloalkane can be found using the general molecular formula.  General molecular formula for cycloalkane is ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n}}$.  The total number of carbon atoms in the given cycloalkane is 7.  This means “n” is seven.  Substitution this is the general molecular formula as shown below, the molecular formula can be obtained.

  $\begin{array}{l}{\text{C}}_{\text{n}}{\text{H}}_{\text{2n}}\\ {\text{C}}_{\text{7}}{\text{H}}_{\text{(2*7)}}\\ {\text{C}}_{\text{7}}{\text{H}}_{\text{14}}\end{array}$

The molecular formula for the given hydrocarbon is found to be ${\text{C}}_{\text{7}}{\text{H}}_{\text{14}}$.

Conclusion

The molecular formula for the given hydrocarbon is found as ${\text{C}}_{\text{7}}{\text{H}}_{\text{14}}$.

(c)

Interpretation Introduction

Interpretation:

Molecular formula for the given hydrocarbon has to be determined.

Concept Introduction:

Organic compounds are the important basis of life.  They include gasoline, coal, dyes, and clothing fibers etc.  The compounds that are obtained from living organisms are termed as organic compounds and those obtained from the earth are known as inorganic compounds.  Organic compounds are found in earth also apart from living organisms.  All the organic compounds contain the element carbon.  Urea was synthesized in the laboratory which is an organic compound.

Hydrocarbons are the organic compounds that contain only hydrogen and carbon atoms.  Hydrocarbon derivatives are the one in which the compounds contain hydrogen and carbon atoms along with one or more additional elements.  The additional elements that can be present in hydrocarbon derivatives are oxygen, nitrogen, sulphur, chlorine, bromine etc.

Hydrocarbons are further classified into two categories.  They are saturated hydrocarbons and unsaturated hydrocarbons.  The hydrocarbons that contain single bonds between carbon atoms in the entire molecule is known as saturated hydrocarbon.  The hydrocarbons that contain atleast one double or triple bond between two carbon atoms in the entire molecule is known as unsaturated hydrocarbon.

Molecular formula of the alkanes can be found by using the general formula ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n+2}}$.  Here, “n” denotes the number of carbon atoms that is present in the structure.

Answer to Problem 12.108EP

The molecular formula for the given hydrocarbon is ${\text{C}}_{\text{7}}{\text{H}}_{\text{16}}$.

Explanation of Solution

Given name of alkane is 2,2-dimethylpentane.  From the name it is understood that the parent alkane is five carbon chain which is pentane.  The substituent present on the hexane are two methyl groups, on the second carbon atom.  Therefore, the line-angle structural formula for 2,2-dimethylpentane can be drawn as shown below,

In line-angle structural representation of molecule, carbon atom is present where two lines meet and at the end of the lines.  In the above structure there are three points where the lines meet and four end points.  Therefore, the total number of carbon atoms present in the given structure is 7.

To determine the molecular formula of alkane, the value of “n” has to be substituted as 7 in the general formula of alkane.

    $\begin{array}{l}\text{General}\text{Molecular}\text{Formula}\text{of}\text{Alkane}\text{=}{\text{C}}_{\text{n}}{\text{H}}_{\text{2n+2}}\\ \text{Molecular}\text{Formula}\text{of}\text{Alkane}\text{=}{\text{C}}_{\text{7}}{\text{H}}_{\text{(2*7+2)}}\\ ={\text{C}}_{\text{7}}{\text{H}}_{16}\end{array}$

Therefore, the molecular formula of the given hydrocarbon is determined as ${\text{C}}_{\text{7}}{\text{H}}_{\text{16}}$.

Conclusion

The molecular formula of the hydrocarbon was determined as ${\text{C}}_{\text{7}}{\text{H}}_{\text{16}}$.

(d)

Interpretation Introduction

Interpretation:

Molecular formula for the given hydrocarbon has to be determined.

Concept Introduction:

Organic compounds are the important basis of life.  They include gasoline, coal, dyes, and clothing fibers etc.  The compounds that are obtained from living organisms are termed as organic compounds and those obtained from the earth are known as inorganic compounds.  Organic compounds are found in earth also apart from living organisms.  All the organic compounds contain the element carbon.  Urea was synthesized in the laboratory which is an organic compound.

Hydrocarbons are the organic compounds that contain only hydrogen and carbon atoms.  Hydrocarbon derivatives are the one in which the compounds contain hydrogen and carbon atoms along with one or more additional elements.  The additional elements that can be present in hydrocarbon derivatives are oxygen, nitrogen, sulphur, chlorine, bromine etc.

Hydrocarbons are further classified into two categories.  They are saturated hydrocarbons and unsaturated hydrocarbons.  The hydrocarbons that contain single bonds between carbon atoms in the entire molecule is known as saturated hydrocarbon.  The hydrocarbons that contain atleast one double or triple bond between two carbon atoms in the entire molecule is known as unsaturated hydrocarbon.

Molecular formula of the alkanes can be found by using the general formula ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n+2}}$.  Here, “n” denotes the number of carbon atoms that is present in the structure.

Answer to Problem 12.108EP

The molecular formula for the given hydrocarbon is ${\text{C}}_{\text{7}}{\text{H}}_{\text{16}}$.

Explanation of Solution

Given name of alkane is 2,3-dimethylpentane.  From the name it is understood that the parent alkane is five carbon chain which is pentane.  The substituent present on the hexane are two methyl groups, each at second and third carbon.  Therefore, the line-angle structural formula for 2,3-dimethylpentane can be drawn as shown below,

In line-angle structural representation of molecule, carbon atom is present where two lines meet and at the end of the lines.  In the above structure there are three points where the lines meet and four end points.  Therefore, the total number of carbon atoms present in the given structure is 7.

To determine the molecular formula of alkane, the value of “n” has to be substituted as 7 in the general formula of alkane.

    $\begin{array}{l}\text{General}\text{Molecular}\text{Formula}\text{of}\text{Alkane}\text{=}{\text{C}}_{\text{n}}{\text{H}}_{\text{2n+2}}\\ \text{Molecular}\text{Formula}\text{of}\text{Alkane}\text{=}{\text{C}}_{\text{7}}{\text{H}}_{\text{(2*7+2)}}\\ ={\text{C}}_{\text{7}}{\text{H}}_{16}\end{array}$

Therefore, the molecular formula of the given hydrocarbon is determined as ${\text{C}}_{\text{7}}{\text{H}}_{\text{16}}$.

Conclusion

The molecular formula of the given hydrocarbon was determined as ${\text{C}}_{\text{7}}{\text{H}}_{\text{16}}$.