Chapter 11, Problem 27P

Give an acceptable IUPAC name for each of the following compounds:

${\text{H}}_{\text{2}}{\text{C=CH(CH}}_{\text{2}}{\text{)}}_{\text{5}}{\text{CH=CH}}_{\text{2}}$

${{\text{(H}}_{\text{2}}\text{C=CH)}}_{\text{3}}\text{CH}$

${\text{H}}_{\text{2}}{\text{C=C=CHCH=CHCH}}_{\text{3}}$

Interpretation Introduction

Interpretation:

The acceptable IUPAC name for each of the given compounds is to be deteremined.

Concept introduction:

Alkanes have the general formula $C_n{H}_{2n+2}$ and they have constitutional isomers with different connectivity of atoms.

The parent chain in each of hydrocarbon structure is first identified and the chain is numbered such that the substituents attached get lowest numbers.

Prefixes are used to denote the number of identical substituents.

The substituents are written in alphabetical order while writing the IUPAC name.

If the two groups of atoms that are the higher priority are on the same side of the double bond, then the bond is termed as the Z-configuration. While if the two group of higher priority are on the opposite side then the configuration is E-configuration.

Answer to Problem 27P

Solution:

a) $1,8-nonadiene$

b) $\text{2,3,4,5-tetramethyl-2,4-hexadiene}$

c) $\text{3-vinyl-1,3-pentadiene}$

d) $\text{(1Z,4Z)-3-(prop-1-en-2-yl)-1,4-cyclohexadiene}$

e) $\text{(1Z,3E,5Z)-1,6-dichloro-1,3,5-hexatriene}$

f) $1,2,4-hexatriene$

g) $(1E,5E,9E)-1,5,9-cyclododecatriene$

h) $\text{(3E)-3-ethyl-4-methylhexadiene}$

Explanation of Solution

a) The expanded structure for the given structure can be drawn as follows:

In the above structure, the parent chain is the continuous chain from $\text{C1}$ to $\text{C9}$, hence its parent name is nonane. There are two double bonds in the given compound, the first one exist in between $\text{C1}$ and $\text{C2}$ carbon atoms and the another double exist in between $\text{C8}$ and $\text{C9}$ carbon atoms so the suffix “diene” is used. There are no other substituents present on any carbon atoms in the chain.

Thus, the IUPAC name is $1,8-nonadiene$.

b) The structure for the given compound is as follows:

In the above structure, the parent longest chain is from $\text{C1}$ to $\text{C6}$ carbon atoms, so the parent name of the given compound is hexane. There are two double bonds in the given compound, the first one exist in between $\text{C2}$ and $\text{C3}$ carbon atoms and the another double exist in between $\text{C4}$ and $\text{C5}$ carbon atoms so the suffix “diene” is used. There are four methyl substituents present on carbon atoms $\text{C2}$, $\text{C3}$, $\text{C4}$, and $\text{C5}$. The prefix “tetra” is used to specify the four methyl substituents in the chain.

Thus, the IUPAC name is $\text{2,3,4,5-tetramethyl-2,4-hexadiene}$.

c) The structure for the given compound and its expanded structure is as follows:

In the above structure, the parent longest chain is from $\text{C1}$ to $\text{C5}$ carbon atoms, so the parent name of the given compound is pentane. There are two double bonds in the given compound, the first one exist in between $\text{C1}$ and $\text{C2}$ carbon atoms and the another double exist in between $\text{C4}$ and $\text{C5}$ carbon atoms so the suffix “diene” is used. There is a vinyl substituent present on the carbon atom $\text{C3}$.

Thus, the IUPAC name is $\text{3-vinyl-1,3-pentadiene}$.

d) The structure for the given compound is as follows:

In the above structure, the parent ring contains six carbon atoms, so the parent name of the cycloalkane is cyclohexane. There are two double bonds in the given compound, the first one exist in between $\text{C1}$ and $\text{C2}$ carbon atoms and the another double exist in between $\text{C4}$ and $\text{C5}$ carbon atoms so the suffix “diene” is used. A substituent containing three carbon atoms (propene) is attached to $\text{C3}$. In this substituent, there is one double bond between two carbon atoms, and it is attached to the parent ring through the double bonded $\text{C2}$ carbon atom of the propene chain.

Considering the Cahn–Ingold–Prelog sequence rules, for the cyclohexadiene, the higher priority groups are on the same side in both the double bonds. Hence, both get the stereochemical label as Z.

Thus, the IUPAC name of this structure is $\text{(1Z,4Z)-3-(prop-1-en-2-yl)-1,4-cyclohexadiene}$.

e) The structure for the given compound is as follows:

In the above structure, the parent longest chain is from $\text{C1}$ to $\text{C6}$ carbon atoms, so the parent name of the given compound is hexane. There are three double bonds in the given compound, the first one exist in between $\text{C1}$ and $\text{C2}$ carbon atoms, the second one is in between $\text{C3}$ and $\text{C4}$, then the third one is exist in between $\text{C5}$ and $\text{C6}$ carbon atoms so the suffix “triene” is used. Two chlorine substituents are attached to the $\text{C1}$ and $\text{C6}$ carbon atoms in the parent chain, so the prefix “di” is used to indicate the presence of two same substituents.

For double bonds at $\text{C1}$ and $\text{C5}$, the higher priority substituents are attached on the same side of the double bond. Thus, they get the stereochemical label Z.

For the internal double bond at carbon $\text{C3}$, the higher priority groups are attached on the opposite side of the double bond. Hence, the internal double bond at $\text{C3}$ gets the stereochemical label E.

Thus, the IUPAC name is $\text{(1Z,3E,5Z)-1,6-dichloro-1,3,5-hexatriene}$.

f) The structure for the given compound is as follows:

In the above structure, the parent longest chain is from $\text{C1}$ to $\text{C6}$ carbon atoms, so the parent name of the given compound is hexane. There are three double bonds in the given compound, the first one exist in between $\text{C1}$ and $\text{C2}$ carbon atoms, the second one is in between $\text{C2}$ and $\text{C3}$, then the third one is exist in between $\text{C4}$ and $\text{C5}$ carbon atoms so the suffix “triene” is used. There are no other substituents present on any carbon atoms in the chain.

Thus, the IUPAC name is $1,2,4-hexatriene$.

g) The structure for the given compound is as follows:

In the above structure, the parent ring contains twelve carbon atoms, so the parent name of the cycloalkane is cyclododecane. There are three double bonds in the given compound, the first one exist in between $\text{C1}$ and $\text{C2}$ carbon atoms, the second one is in between $\text{C5}$ and $\text{C6}$, then the third one is exist in between $\text{C9}$ and $\text{C10}$ carbon atoms so the suffix “triene” is used.

For all the three double bonds at $\text{C1}$, $\text{C5}$, and $\text{C9}$, the higher priority groups (considering the Cahn–Ingold–Prelog sequence rules) are on the opposite sides; hence, they get the stereochemical label E.

Thus, the IUPAC name of this structure is $(1E,5E,9E)-1,5,9-cyclododecatriene$.

h) The structure for the given compound is as follows:

In the above structure, the parent longest chain is from $\text{C1}$ to $\text{C6}$ carbon atoms, so the parent name of the given compound is hexane. There are two double bonds in the given compound, the first one exist in between $\text{C1}$ and $\text{C2}$ carbon atoms and the another double exist in between $\text{C3}$ and $\text{C4}$ carbon atoms so the suffix “diene” is used. The substituent attached at $\text{C3}$ is an ethyl substituent. The substituent attached to $\text{C4}$ is a methyl substituents. The substituents attached on the parent chain are to be written in alphabetical order.

For the double bonds at $\text{C3}$, the higher priority groups are on the opposite side of the double bond. Hence, it gets the stereochemical label as E.

Thus, the IUPAC name is $\text{(3E)-3-ethyl-4-methylhexadiene}$.