Chapter 21, Problem 21.3TC

Interpretation Introduction

(a)

Interpretation:

From the following hydrocarbons, alkane is to be identified.

${\text{C}}_{\text{7}}{\text{H}}_{\text{16}}$, ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$, ${\text{C}}_{\text{11}}{\text{H}}_{\text{22}}$, ${\text{C}}_{\text{9}}{\text{H}}_{\text{20}}$.

Concept introduction:

Hydrocarbons contain carbon and hydrogen atoms. Alkanes are saturated hydrocarbons where the carbon is bonded to four other carbon atoms by a single bond.

Answer to Problem 21.3TC

Among the given hydrocarbons ${\text{C}}_{\text{7}}{\text{H}}_{\text{16}}$ and ${\text{C}}_{\text{9}}{\text{H}}_{\text{20}}$ are normal alkanes. ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ and ${\text{C}}_{\text{11}}{\text{H}}_{\text{22}}$ are cycloalkanes.

Explanation of Solution

Alkanes are the saturated hydrocarbons in which each carbon atom is bonded to four other atoms via single bond only. The alkanes general formula of is ${\text{C}}_n{\text{H}}_{2n+2}$, $n$ is the number of carbon atoms. If all the carbon atoms in alkane are arranged in a linear or continuous chain, the resulting hydrocarbon is called normal alkane. For example, methane $\left({\text{CH}}_{\text{4}}\right)$ and ethane $\left({\text{C}}_{\text{2}}{\text{H}}_{\text{6}}\right)$.

According to the general formula of alkanes, for 7 carbon atoms there must be 16 hydrogen atoms and for 9 carbon atoms, there must be 20 hydrogen atoms. Hydrocarbons ${\text{C}}_{\text{7}}{\text{H}}_{\text{16}}$ and ${\text{C}}_{\text{9}}{\text{H}}_{\text{20}}$ satisfies the general formula for alkanes thus these are normal alkane.

According to the general formula of alkanes, for 5 carbon atoms there must be 12 hydrogen atoms and for 11 carbon atoms, there must be 24 hydrogen atoms. Hydrocarbons ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ and ${\text{C}}_{\text{11}}{\text{H}}_{\text{22}}$ does not satisfy the general formula for alkanes rather there have two hydrogen atoms short. ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ and ${\text{C}}_{\text{11}}{\text{H}}_{\text{22}}$ are cycloalkanes and not normal alkanes.

Conclusion

Among the given hydrocarbons ${\text{C}}_{\text{7}}{\text{H}}_{\text{16}}$ and ${\text{C}}_{\text{9}}{\text{H}}_{\text{20}}$ are normal alkanes. ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ and ${\text{C}}_{\text{11}}{\text{H}}_{\text{22}}$ are cycloalkanes.

Interpretation Introduction

(b)

Interpretation:

The formula of the alkyl group derived from pentane is to be identified.

Concept introduction:

An alkyl group is derived from the respective alkane. Alkyl group is an alkane with one hydrogen atom less than the respective alkane. The alkyl group is named after alkane counterpart containing the same number of carbon atoms by replacing the “ane” suffix to “yl”.

Answer to Problem 21.3TC

The formula of the alkyl group obtained from pentane is $-{\text{C}}_{\text{5}}{\text{H}}_{\text{11}}$.

Explanation of Solution

The molecular formula of pentane is ${\text{C}}_{\text{5}}{\text{H}}_{\text{12}}$ and the corresponding alkyl group is $-{\text{C}}_{\text{5}}{\text{H}}_{\text{11}}$.

Conclusion

The formula of the alkyl group derived from pentane is $-{\text{C}}_{\text{5}}{\text{H}}_{\text{11}}$.

Interpretation Introduction

(c)

Interpretation:

The structural diagram of $\text{3, 3-difluoro-4-iododecane}$ is to be drawn.

Concept introduction:

Lewis diagram is the representation of the molecules or ions. It shows the bonding between the atoms and also shows the unshared pairs of electrons on an atom if any. The structural formula or structural diagram is nothing but Lewis structure without unshared pairs of electrons.

In the IUPAC name of an organic compound represents the number of the substituent and the numbers before the Greek prefix represent the position of the substituents. The suffix for an alkane is ‘ane. The number of carbon atoms in the parent hydrocarbon chain is represented by the root name. For example: ‘prop’ represent 3 carbon atoms present in the parent hydrocarbon chain.

Answer to Problem 21.3TC

The structural diagram of $\text{3, 3-difluoro-4-iododecane}$ is,

Explanation of Solution

The IUPAC name of the hydrocarbon is $\text{3, 3-difluoro-4-iododecane}$. The parent carbon chain has 10 carbon atoms as indicated by the root name decane. The other substituents attached to the chain are 2 fluorine atoms and one iodine atom. 2 fluorine atoms are attached at the C-3 position and iodine is attached to a C-4 carbon atom.

The structura diagram is,

Conclusion

The structural diagram of $\text{3, 3-difluoro-4-iododecane}$ is,

Interpretation Introduction

(d)

Interpretation:

The structural diagram of $\text{1, 1-diethylcycohexane}$ is to be drawn.

Concept introduction:

Lewis diagram is the representation of the molecule or ion. It shows the bonding between the atoms and also shows the unshared pairs of electrons on an atom if any. The structural formula or structural diagram is nothing but Lewis structure without unshared pairs of electrons.

In the IUPAC name of an organic compound, the Greek prefix represents the number of the substituent and the numbers before the Greek prefix represent the position of the substituents. The suffix for an alkane is ‘ane and the prefix ‘cyclo’ is used for cycloalkanes. The number of carbon atoms in the parent hydrocarbon chain is represented by the root name. For example: ‘prop’ represent 3 carbon atoms present in the parent hydrocarbon chain.

Answer to Problem 21.3TC

The structural diagram of $\text{1, 1-diethylcycohexane}$ is,

Explanation of Solution

The IUPAC name of the hydrocarbon is $\text{1, 1-diethylcycohexane}$. The name of the hydrocarbon has prefix cyclo- this suggests that it is a cycloalkane with 6 carbon atoms. Two ethyl groups are attached to the first carbon atom as indicated by the prefix name $\text{1, 1-diethyl}$.

Conclusion

The structural diagram of $\text{1, 1-diethylcycohexane}$ is,