Chapter 11, Problem 11.7E

(a)

Interpretation Introduction

Interpretation:

The systematic name of the compound ${\text{CH}}_{\text{2}}\text{=C}{\left({\text{CH}}_{\text{3}}\right)}_{\text{2}}$ has to be given and the geometrical isomers (if any) have to be identified.

Concept Introduction:

Alkenes:  The simplest unsaturated hydrocarbon with a double bond is called as alkene.  The name of alkane ends with “-ene”.

Rules for naming compound:

1. 1) The carbon atoms in the longest chain have to be counted.
2. 2) The substituents and multiple bonds have to be identified and counted and the suffix “-ene” is added.
3. 3) The backbone carbon atoms have to be numbered by assigning the lowest number from the starting end that contains the double bond.

Alkynes:  Alkynes are hydrocarbons with one carbon-carbon triple bond.  The name of the alkyne ends with “-yne”.

Rules for naming compound:

1. 1) The carbon atoms in the longest chain have to be counted.
2. 2) The substituents and multiple bonds have to be identified and counted and the suffix “-yne” is added.
3. 3) The backbone carbon atoms have to be numbered by assigning the lowest number from the starting end that contains the double bond.

Geometrical isomers:  In geometrical isomers, atoms have different arrangements on either side of a double bond above or below the ring of a cycloalkane or cycloalkane.  If the atoms are present on the same side of the double bond, then it is cis-isomer and if they are present on the opposite side of the double bond, then it is trans-isomer.

Answer to Problem 11.7E

The systematic name of the compound ${\text{CH}}_{\text{2}}\text{=C}{\left({\text{CH}}_{\text{3}}\right)}_{\text{2}}$ is $\text{2-methyl-1-propene}\text{.}$

The geometrical isomers are not possible in $\text{2-methyl-1-propene}\text{.}$

Explanation of Solution

The given compound is,

The compound is identified as alkene.  The parent chain of the compound is propane.  One methyl group is present in the carbon second position and a double bond is seen at the carbon first position.  Hence, the systematic name of the compound is $\text{2-methyl-1-propene}\text{.}$

The geometrical isomers are not possible in $\text{2-methyl-1-propene}\text{.}$

(b)

Interpretation Introduction

Interpretation:

The systematic name of the compound ${\text{CH}}_{\text{3}}\text{CH=C}\left({\text{CH}}_{\text{3}}\right){\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ has to be given and the geometrical isomers (if any) have to be identified.

Concept Introduction:

Refer to part (a).

Answer to Problem 11.7E

The systematic name of the compound ${\text{CH}}_{\text{3}}\text{CH=C}\left({\text{CH}}_{\text{3}}\right){\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ is $\text{3-methyl-2-pentene}\text{.}$

Cis-$\text{3-methyl-2-pentene}$ and trans-$\text{3-methyl-2-pentene}$ are possible in $\text{3-methyl-2-pentene}\text{.}$

Explanation of Solution

The given compound is,

The compound is identified as alkene.  The parent chain of the compound is pentane.  One methyl group is present in the carbon third position and a double bond is seen at the carbon second position.  Hence, the systematic name of the compound is $\text{3-methyl-2-pentene}\text{.}$

Cis-$\text{3-methyl-2-pentene}$ and trans-$\text{3-methyl-2-pentene}$ are possible in $\text{3-methyl-2-pentene}\text{.}$

(c)

Interpretation Introduction

Interpretation:

The systematic name of the compound $\text{HC}\equiv {\text{CCH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ has to be given and the geometrical isomers (if any) have to be identified.

Concept Introduction:

Refer to part (a).

Answer to Problem 11.7E

The systematic name of the compound $\text{HC}\equiv {\text{CCH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ is $\text{1-hexyne}\text{.}$

No geometrical isomers are possible in $\text{1-hexyne}\text{.}$

Explanation of Solution

The given compound is,

The compound is identified as alkyne.  The parent chain of the compound is hexane.  One triple bond is present in carbon first position.  Hence, the systematic name of the compound is $\text{1-hexyne}\text{.}$

Geometrical isomers are not possible because triple bond has only one substituent each.

(d)

Interpretation Introduction

Interpretation:

The systematic name of the compound ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{C}\equiv {\text{CCH}}_{\text{2}}{\text{CH}}_{\text{3}}$ has to be given and the geometrical isomers (if any) have to be identified.

Concept Introduction:

Refer to part (a).

Answer to Problem 11.7E

The systematic name of the compound ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{C}\equiv {\text{CCH}}_{\text{2}}{\text{CH}}_{\text{3}}$ is $\text{3-hexyne}\text{.}$

No geometrical isomers are possible in $\text{3-hexyne}\text{.}$

Explanation of Solution

The given compound is,

The compound is identified as alkyne.  The parent chain of the compound is hexane.  One triple bond is present in carbon third position.  Hence, the systematic name of the compound is $\text{3-hexyne}\text{.}$

Geometrical isomers are not possible because triple bond has only one substituent each.

(e)

Interpretation Introduction

Interpretation:

The systematic name of the compound ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{C}\equiv {\text{CCH}}_{\text{3}}$ has to be given and the geometrical isomers (if any) have to be identified.

Concept Introduction:

Refer to part (a).

Answer to Problem 11.7E

The systematic name of the compound ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{C}\equiv {\text{CCH}}_{\text{3}}$ is $\text{2-hexyne}\text{.}$

No geometrical isomers are possible in $\text{2-hexyne}\text{.}$

Explanation of Solution

The given compound is,

The compound is identified as alkyne.  The parent chain of the compound is hexane.  One triple bond is present in carbon second position.  Hence, the systematic name of the compound is $\text{2-hexyne}\text{.}$

Geometrical isomers are not possible because triple bond has only one substituent each.