Chapter 19, Problem 27PE

(a)

Interpretation Introduction

Interpretation:

Structural formula of 2,5-dimethyl-3-hexane has to be drawn.

Concept introduction:

IUPAC Nomenclature:

IUAC gives rules for the naming of chemical compounds. These rules are,

For unsaturated hydrocarbons, longest chain is the parent chain of the compound and remaining groups and atoms are consider as substituent.

In the nomenclature, Find the parent chin first then number the carbon atoms in the parent chain by giving lest number to the unsaturated double/triple bonded carbon followed by designate the substituent in its position in parent chain.

If more than one same substituent were occurs, add a prefix (di-, tri-, tetra-, ect..) in front of parent chain name.

If compound contains double bond means, name end with suffix of ene or if compound contains triple bond means name end with suffix of yne.

Finally the systematic name was written as, the substituent position number with prefix (di-, tri-, tetra-, ect..) of number of substituents followed by name of the substituent then write the parent chain name (which contains large number of carbon atoms in the chain) with suffix of suffix ene/yne.

The parent chain names based on the carbon atoms are,

$\begin{array}{l}\text{Alkenes}\\ {\text{CH}}_2{\text{=CH}}_2\text{Ethene}\\ {\text{CH}}_2{\text{=CH-CH}}_3\text{Propene}\\ {\text{CH}}_2{\text{=CH-CH}}_{\text{2}}{\text{-CH}}_3\text{Butene}\\ {\text{CH}}_2{\text{=CH-CH}}_{\text{2}}{\text{-CH}}_{\text{2}}\text{-}{\text{CH}}_3\text{Pentene, etc}\mathrm{..}.\end{array}$          $\begin{array}{l}\text{Alkyne}\\ \text{CH}\equiv \text{CH }\text{Ethyne}\\ \text{CH}\equiv {\text{C-CH}}_3\text{Propyne}\\ \text{CH}\equiv {\text{C-CH}}_{\text{2}}{\text{-CH}}_3\text{Butyne}\\ \text{CH}\equiv {\text{C-CH}}_{\text{2}}{\text{-CH}}_{\text{2}}\text{-}{\text{CH}}_3\text{Pentyne, ect}\mathrm{...}\end{array}$

The substituent names based on the carbon atoms are,

$\begin{array}{l}{\text{CH}}_{\text{3}}\text{-}\text{methyl}\\ {\text{CH}}_{\text{3}}{\text{-CH}}_{\text{2}}\text{- }\text{ethyl}\\ {\text{CH}}_{\text{3}}{\text{-CH}}_{\text{2}}{\text{-CH}}_{\text{2}}\text{-}\text{propyl}\end{array}$

Explanation of Solution

The structural formula of 2,5-dimethyl-3-hexene is,

From the given name parent compound is 3-hexene, its structure is,

Two methyl groups are present at 2 and 5 positions so substitute methyl groups at 2 and 5 positions to get the complete structural formula of 2,5-dimethyl-3-hexene.

Hence, the complete structural formula of 2,5-dimethyl-3-hexene is,

(b)

Interpretation Introduction

Interpretation:

Structural formula of 2-ethyl-3-methyl-1-pentene has to be drawn.

Concept introduction:

Refer part (a).

Explanation of Solution

The structural formula of 2-ethyl-3-methyl-1-pentene is,

From the given name parent compound is 1-pentene, its structure is,

Ethyl group is present at second carbon and methyl group is present at third carbon so substitute these carbon atoms to get structural formula of 2-ethyl-3-methyl-1-pentene.

Hence, the complete structural formula of 2-ethyl-3-methyl-1-pentene is,

(c)

Interpretation Introduction

Interpretation:

Structural formula of 4-methyl-2-pentene has to be drawn.

Concept introduction:

Refer part (a).

Explanation of Solution

The structural formula of 4-methyl-2-pentene is,

From the given name parent compound is 4-methyl-2-pentene, its structure is,

Methyl group is present at fourth carbon so substitute methyl group at 4 carbon atom to get structural formula of 4-methyl-2-pentene.

Hence, the complete structural formula of 4-methyl-2-pentene is,