Chapter 10, Problem 10.108QP

Interpretation Introduction

Interpretation:

Possible monochlorinated products has to be given and the products has to be named using IUPAC nomenclature.

Concept Introduction:

Halogenation reaction is the one where atom or atoms of halogens get substituted in a carbon chain.  Halogenation is a type of substitution reaction.

In alkanes, substitution reaction means, a group or atom being substituted for one of the hydrogen atoms.  As all the four bonds that can be formed from carbon in case of alkanes is four single bonds, halogenation reaction in case of alkane will be substitution only.  Product obtained on halogenation of alkane is alkyl halides.

IUPAC rules for naming alkanes:

There are about five rules that has to be followed for naming an alkane and they are,

• The longest continuous carbon chain in the compound has to be identified.  This is known as parent compound.  From this the parent name is obtained.  Suffix “–ane” (for alkane) is added at the end of the prefix which gives information about the number of carbon atoms.
• Numbering has to be done so that the lowest number is given to the first group that is encountered in the parent chain.
• Naming and numbering has to be given for each atom or group that is attached to the parent chain.  Numbering has to be done in a way that substituents get the least numbering.
• If the same substitution is present in the parent chain more than once, a separate prefix is added which tells about the number of times the substituent occurs.  Prefixes used are di-, tri-, tetra-, penta- etc.
• Name of the substituents has to be placed in an alphabetical order before the parent compound name.

Explanation of Solution

Structure of given alkane is,

Monochlorination of ${\text{CH}}_{\text{3}}{\text{CH(CH}}_{\text{3}}{\text{)CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ results in formation of five products.  Molecular formula of the given compound is ${\text{C}}_{\text{5}}{\text{H}}_{\text{12}}$.  Chlorination is a substitution reaction and hence, the monochlorinated product will have the molecular formula of ${\text{C}}_{\text{5}}{\text{H}}_{\text{11}}\text{Br}$.  As there are five carbon atoms that have different environment are present in given compound, five monochlorinated products are obtained.  The balanced equation can be given as,

  $\begin{array}{l}{\text{CH}}_{\text{3}}{\text{CH(CH}}_{\text{3}}{\text{)CH}}_{\text{2}}{\text{CH}}_{\text{3}}\text{+}{\text{Cl}}_{\text{2}}\stackrel{\text{light}\text{or}\text{heat}}{\to }{\text{CH}}_{\text{3}}{\text{CH(CH}}_{\text{3}}{\text{)CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{Cl}\text{+}\text{HCl}\\ {\text{CH}}_{\text{3}}{\text{CH(CH}}_{\text{3}}{\text{)CH}}_{\text{2}}{\text{CH}}_{\text{3}}\text{+}{\text{Cl}}_{\text{2}}\stackrel{\text{light}\text{or}\text{heat}}{\to }{\text{CH}}_{\text{3}}{\text{CH(CH}}_{\text{3}}{\text{)CHClCH}}_{\text{3}}\text{+}\text{HCl}\\ {\text{CH}}_{\text{3}}{\text{CH(CH}}_{\text{3}}{\text{)CH}}_{\text{2}}{\text{CH}}_{\text{3}}\text{+}{\text{Cl}}_{\text{2}}\stackrel{\text{light}\text{or}\text{heat}}{\to }{\text{CH}}_{\text{3}}{\text{CH(CH}}_{\text{2}}{\text{Cl)CH}}_{\text{2}}{\text{CH}}_{\text{3}}\text{+}\text{HCl}\\ {\text{CH}}_{\text{3}}{\text{CH(CH}}_{\text{3}}{\text{)CH}}_{\text{2}}{\text{CH}}_{\text{3}}\text{+}{\text{Cl}}_{\text{2}}\stackrel{\text{light}\text{or}\text{heat}}{\to }{\text{CH}}_{\text{3}}{\text{CCl(CH}}_{\text{3}}{\text{)CH}}_{\text{2}}{\text{CH}}_{\text{3}}\text{+}\text{HCl}\\ {\text{CH}}_{\text{3}}{\text{CH(CH}}_{\text{3}}{\text{)CH}}_{\text{2}}{\text{CH}}_{\text{3}}\text{+}{\text{Cl}}_{\text{2}}\stackrel{\text{light}\text{or}\text{heat}}{\to }{\text{CH}}_{\text{2}}{\text{ClCH(CH}}_{\text{3}}{\text{)CH}}_{\text{2}}{\text{CH}}_{\text{3}}\text{+}\text{HCl}\end{array}$

IUPAC name for ${\text{CH}}_{\text{3}}{\text{CH(CH}}_{\text{3}}{\text{)CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{Cl}$:

In the given compound, the longest carbon chain is found to contain four carbon atoms.  Therefore, the parent alkane name is butane.

Numbering of carbon atoms has to be done in a way that the substituents present in the longest carbon chain get the least numbering.

The substituent present in the given compound are a chlorine atom and a methyl group.  Number has to be added before the substituent indicating the carbon in which it is attached.  Therefore, IUPAC name is obtained as,

Parent chain is butane and the substituent present is 1-chloro-3-methyl.  Hence, the IUPAC name is given as 1-chloro-3-methylbutane.

IUPAC name for ${\text{CH}}_{\text{3}}{\text{CH(CH}}_{\text{3}}{\text{)CHClCH}}_{\text{3}}$:

In the given compound, the longest carbon chain is found to contain four carbon atoms.  Therefore, the parent alkane name is butane.

Numbering of carbon atoms has to be done in a way that the substituents present in the longest carbon chain get the least numbering.

The substituent present in the given compound are a chlorine atom and a methyl group.  Number has to be added before the substituent indicating the carbon in which it is attached.  Therefore, IUPAC name is obtained as,

Parent chain is butane and the substituent present is 2-chloro-3-methyl.  Hence, the IUPAC name is given as 2-chloro-3-methylbutane.

IUPAC name for ${\text{CH}}_{\text{3}}{\text{CH(CH}}_{\text{2}}{\text{Cl)CH}}_{\text{2}}{\text{CH}}_{\text{3}}$:

In the given compound, the longest carbon chain is found to contain four carbon atoms.  Therefore, the parent alkane name is butane.

Numbering of carbon atoms has to be done in a way that the substituents present in the longest carbon chain get the least numbering.

The substituent present in the given compound are a chloromethyl group.  Number has to be added before the substituent indicating the carbon in which it is attached.  Therefore, IUPAC name is obtained as,

Parent chain is butane and the substituent present is 2-chloromethyl.  Hence, the IUPAC name is given as 2-chloromethylbutane.

IUPAC name for ${\text{CH}}_{\text{3}}{\text{CCl(CH}}_{\text{3}}{\text{)CH}}_{\text{2}}{\text{CH}}_{\text{3}}$:

In the given compound, the longest carbon chain is found to contain four carbon atoms.  Therefore, the parent alkane name is butane.

Numbering of carbon atoms has to be done in a way that the substituents present in the longest carbon chain get the least numbering.

The substituent present in the given compound are a chlorine atom and a methyl group.  Number has to be added before the substituent indicating the carbon in which it is attached.  Therefore, IUPAC name is obtained as,

Parent chain is butane and the substituent present is 2-chloro-2-methyl.  Hence, the IUPAC name is given as 2-chloro-2-methylbutane.

IUPAC name for ${\text{CH}}_{\text{2}}{\text{ClCH(CH}}_{\text{3}}{\text{)CH}}_{\text{2}}{\text{CH}}_{\text{3}}$:

In the given compound, the longest carbon chain is found to contain four carbon atoms.  Therefore, the parent alkane name is butane.

Numbering of carbon atoms has to be done in a way that the substituents present in the longest carbon chain get the least numbering.

The substituent present in the given compound are a chlorine atom and a methyl group.  Number has to be added before the substituent indicating the carbon in which it is attached.  Therefore, IUPAC name is obtained as,

Parent chain is butane and the substituent present is 1-chloro-2-methyl.  Hence, the IUPAC name is given as 1-chloro-2-methylbutane.