Question

Question: Draw the eight constitutional isomers having the molecular formula C₅H₁₁Cl .

1. Give the IUPAC name for each compound (ignoring R and S designations).
2. Classify each alkyl halide as $1°,2°or3°$.
3. Label any stereogenic centers.
4. For each constitutional isomer that contains a stereogenic center, draw all possible stereoisomers, and label each stereogenic center as R or S.

Short answer

ANSWER

a.

b.

c.

d.

Step-by-step solution

Constitutional isomers

Compounds that have the same molecular formula but different structural arrangements/formula are termed constitutional isomers.

Nomenclature of organic compounds

Steps involved in the IUPAC naming of organic compounds are as follows:

• The longest carbon chain is taken as the parent.
• Number the atoms present in the parent chain in a manner that the carbon atom bearing the substituents (if any) gets the least possible number.
• Name and number the substituents.
• Combine all and arrange in alphabetical order.

Stereogenic center

A point in a molecule that gives rise to different stereoisomers on interchanging any two groups connected to it is termed stereogenic centers.

R and S configurations are assigned to the stereogenic centers by assigning priorities to the groups attached to them (according to the Cahn-Ingold Prelog rules).

If the orientation from priority one to four is clockwise, the center is assigned R configuration, and if it is counterclockwise, it is assigned S configuration.

If the orientation or projection of the least priority group is toward the observer (indicated by a wedge bond), then the obtained configuration needs to be reversed.

Constitutional isomers having the molecular formula C5H11Cl . 

The constitutional isomers having the mole molecular formula C₅H₁₁Cl. along with their IUPAC names are provided below:

Constitutional isomers having the formula

Classifying the alkyl halides as primary 1° , secondary 2° , and tertiary 3° .

The haloalkane in which the halogen is attached to a carbon atom that is connected to another carbon is termed a primary halide.

The one in which the carbon is connected to two other carbons is termed secondary and the one in which it is connected to three other carbon atoms is named tertiary.

Primary, secondary, and tertiary alkyl chlorides

Stereogenic centers and their stereoisomers

The isomers having stereogenic centers and their stereoisomers are provided below.

• 2-chloropentane

2-chloropentane and its stereoisomers

• 2-chloropentane and its stereoisomers

2-chloro-3-methylbutane and its stereoisomers

• 1-chloro-2-methylbutane

1-chloro-2-methylbutane and its stereoisomer