Chapter 23, Problem 23.23QP

(a)

Interpretation Introduction

Interpretation:

Molecular formula for the given set of compounds has to be written.

Concept Introduction:

Molecular formula of a compound represents the total number of atoms that is present in it.  It does not give any other information about the functional group, etc present in the compound.  Simply it gives how many number of atoms are present for each element that is present in the compound.

To Write: The molecular formula for the given ball-stick models.

Answer to Problem 23.23QP

The molecular formula for the first structure is ${\text{C}}_{\text{3}}{\text{H}}_{\text{9}}\text{N}$ and the name is Triethylamine

The molecular formula for the second structure is ${\text{C}}_{\text{2}}{\text{H}}_{\text{4}}\text{O}$ and the name is acetaldehyde.

The molecular formula for the third structure is ${\text{C}}_{\text{3}}{\text{H}}_{\text{8}}\text{O}$ and the name is 2-propanol.

The molecular formula for the fourth structure is ${\text{C}}_{\text{2}}{\text{H}}_{\text{4}}{\text{O}}_{\text{2}}$ and the name is acetic acid.

Explanation of Solution

For First structure:

In the given ball-stick model, the black spheres are carbon atoms, light blue spheres are hydrogen atoms and dark blue spheres are nitrogen atoms.  The total number of black spheres is 3, while that of light blue spheres is 9 and dark blue spheres is 1.  Hence we arrive at the molecular formula of ${\text{C}}_{\text{4}}{\text{H}}_{\text{9}}\text{N}$.

For Second structure:

In the given ball-stick model, the black spheres are carbon atoms, light blue spheres are hydrogen atoms and red spheres are oxygen atoms.  The total number of black spheres is 2, while that of light blue spheres is 4 and red spheres is 1.  Hence we arrive at the molecular formula of ${\text{C}}_{\text{2}}{\text{H}}_{\text{4}}\text{O}$.

For Third structure:

In the given ball-stick model, the black spheres are carbon atoms, light blue spheres are hydrogen atoms and red spheres are oxygen atoms.  The total number of black spheres is 3, while that of light blue spheres is 8 and red spheres is 1.  Hence we arrive at the molecular formula of ${\text{C}}_{\text{3}}{\text{H}}_{\text{8}}\text{O}$.

For Fourth structure:

In the given ball-stick model, the black spheres are carbon atoms, light blue spheres are hydrogen atoms and red spheres are oxygen atoms.  The total number of black spheres is 2, while that of light blue spheres is 4 and red spheres is 2.  Hence we arrive at the molecular formula of ${\text{C}}_{\text{2}}{\text{H}}_{\text{4}}{\text{O}}_{\text{2}}$.

Conclusion

The molecular formula for the given ball-stick model compounds are written.

(b)

Interpretation Introduction

Interpretation:

Condensed structural formula for the given ball-stick model compounds has to be written.

Concept Introduction:

Condensed structural formula is representation of the organic compound.  In this the lengthy carbon chain is shown only with the carbon atoms (along with the hydrogen) without any bonds.  The additional branches are shown with explicit bonds.

To Write: The condensed structural formula for the given set of ball-stick model compounds.

Answer to Problem 23.23QP

The condensed structural formula of First structure is ${\text{N(CH}}_{\text{3}}{\text{)}}_{\text{3}}$.

The condensed structural formula for the Second structure is,

The condensed structural formula for the Third structure is,

The condensed structural formula for the Fourth structure is,

Explanation of Solution

For First structure:

Condensed structural formula can be drawn considering the skeleton in the given ball-stick model.  Nitrogen is the central atom which is bonded to three methyl groups.  The single bonds between the nitrogen and methyl group are removed to obtain the condensed structural formula as shown below,

For Second structure:

Condensed structural formula can be drawn considering the carbon skeleton in the given ball-stick model.  The carbon chain is drawn.  One of the carbon atom is attached to an oxygen atom and a hydrogen atom.  The single bonds are removed in the parent structure which results in the condensed structural formula as shown below,

For Third structure:

Condensed structural formula can be drawn considering the carbon skeleton in the given ball-stick model.  The carbon chain is drawn.  The carbon atom in the middle is attached to an hydroxy group.  The single bonds are removed in the parent structure which results in the condensed structural formula as shown below,

For Fourth structure:

Condensed structural formula can be drawn considering the carbon skeleton in the given ball-stick model.  The carbon chain is drawn.  One of the carbon atom is attached to an hydroxy group and an oxygen atom.  This means it is an carboxylic acid.  The single bonds are removed in the parent structure which results in the condensed structural formula as shown below,

Conclusion

The condensed structural formula are written for the given ball-stick model representation of compounds.

(c)

Interpretation Introduction

Interpretation:

The functional group present in the given set of ball-stick models has to be identified.

Concept Introduction:

In an organic compound, the reactive portion is known as functional group.  This undergoes reactions with other reagents and this does not depend upon how the rest of the compound is like.  Few of the common functional groups are alcohol, ester, carboxylic acid, ketone, aldehyde etc.  Functional group determines the nature of the compound.

To Identify: The functional group present in the given ball-stick models

Answer to Problem 23.23QP

The functional group present in First structure is identified as amine (tertiary amine)

The functional group present in Second structure is identified as aldehyde.

The functional group present in Third structure is identified as alcohol.

The functional group present in Fourth structure is identified as carboxylic acid.

Explanation of Solution

For First structure:

By looking at the formula of the given compound we can identify that a nitrogen is present in it.  If nitrogen is present in a compound we can classify it as amine.  In this case the nitrogen does not have any hydrogen atom bonded to it.  Hence, it is a tertiary amine.  The functional group is highlighted in red colour as shown.

For Second structure:

By looking at the formula of the given compound we can identify that a carbonyl group is present in it.  The carbonyl group is attached to a hydrogen atom on one side and an alkyl group on other.  Hence, this compound falls under the category of aldehyde.

For Third structure:

By looking at the formula of the given compound we can identify that a hydroxy group is present in it.  The hydroxy group is attached to a carbon atom which bears only one hydrogen atoms.  Hence, this compound falls under the category of secondary alcohol.

For Fourth structure:

By looking at the formula of the given compound we can identify that a carboxylic acid group is present in it.  The carboxylic acid group is the functional group in this compound.  Therefore, the compound falls under the category of carboxylic acid.

Conclusion

The functional groups present in the given set of ball-stick model compounds are identified.