Chapter 10, Problem 10.103QP

(a)

Interpretation Introduction

Interpretation:

Constitutional isomers that has molecular formula ${\text{C}}_{\text{6}}{\text{H}}_{\text{14}}$ has to be drawn and named.  The one that gives two monobromo derivatives when treated with bromine has to be given.

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

Given molecular formula of constitutional isomer is ${\text{C}}_{\text{6}}{\text{H}}_{\text{14}}$.  The various possible structural formula for the constitutional isomers and IUPAC name are,

Among the constitutional isomers, the one that gives only two monobromo derivatives can be identified by looking into the structure that contain carbon atoms that has only two different environment.  The structure is found to be 2,3-dimethylbutane.

The reaction can be given as,

IUPAC names:

First monobromo derivative:

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 bromine atom and two methyl groups.  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-bromo-2,3-dimethyl.  Hence, the IUPAC name is given as 1-bromo-2,3-dimethylbutane.

Second monobromo derivative:

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 bromine atom and two methyl groups.  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-bromo-2,3-dimethyl.  Hence, the IUPAC name is given as 2-bromo-2,3-dimethylbutane.

(b)

Interpretation Introduction

Interpretation:

Constitutional isomers that has molecular formula ${\text{C}}_{\text{6}}{\text{H}}_{\text{14}}$ has to be drawn and named.  The one that gives three monobromo derivatives when treated with bromine has to be given.

Concept Introduction:

Refer part (a).

Explanation of Solution

Given molecular formula of constitutional isomer is ${\text{C}}_{\text{6}}{\text{H}}_{\text{14}}$.  The various possible structural formula for the constitutional isomers and IUPAC name are,

Among the constitutional isomers, the one that gives only three monobromo derivatives can be identified by looking into the structure that contain carbon atoms that has only three different environment.  The structure is found to be hexane.

The reaction can be given as,

IUPAC names:

First monobromo derivative:

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

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 is a bromine atom.  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 hexane and the substituent present is 1-bromo.  Hence, the IUPAC name is given as 1-bromohexane.

Second monobromo derivative:

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

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 is a bromine atom.  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 hexane and the substituent present is 2-bromo.  Hence, the IUPAC name is given as 2-bromohexane.

Third monobromo derivative:

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

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 is a bromine atom.  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 hexane and the substituent present is 3-bromo.  Hence, the IUPAC name is given as 3-bromohexane.

(c)

Interpretation Introduction

Interpretation:

Constitutional isomers that has molecular formula ${\text{C}}_{\text{6}}{\text{H}}_{\text{14}}$ has to be drawn and named.  The one that gives only four monobromo derivatives when treated with bromine has to be given.

Concept Introduction:

Refer part (a).

Explanation of Solution

Given molecular formula of constitutional isomer is ${\text{C}}_{\text{6}}{\text{H}}_{\text{14}}$.  The various possible structural formula for the constitutional isomers and IUPAC name are,

Among the constitutional isomers, the one that gives only four monobromo derivatives can be identified by looking into the structure that contain carbon atoms that has only four different environment.  The structure is found to be 3-methylpentane.

The reaction can be given as,

IUPAC names:

First monobromo derivative:

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

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 bromine 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 pentane and the substituent present is 1-bromo-3-methyl.  Hence, the IUPAC name is given as 1-bromo-3-methylpentane.

Second monobromo derivative:

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

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 bromine 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 pentane and the substituent present is 2-bromo-3-methyl.  Hence, the IUPAC name is given as 2-bromo-3-methylpentane.

Third monobromo derivative:

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

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 bromine 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 pentane and the substituent present is 3-bromo-3-methyl.  Hence, the IUPAC name is given as 3-bromo-3-methylpentane.

Fourth monobromo derivative:

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

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 is a bromomethyl 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 pentane and the substituent present is 3-bromomethyl.  Hence, the IUPAC name is given as 3-bromomethylpentane.