Question

Draw the structure and give the systematic name for a compound with molecular formula C₅H₁₂ that has

a. only primary and secondary hydrogens.

b. only primary hydrogens.

c. one tertiary hydrogen.

d. two secondary hydrogens.

Short answer

Because pentane is the name of the parent hydrocarbon with the molecular formula the longest continuous chain has 5 carbons. Now, draw and number the parent hydrocarbon.

Determine substituents

Now, arrange the parentcarbon in such a way so that contains only primary and secondary hydrogen.

• A primary hydrogen is a hydrogen that is attached to a primary carbon (-CH₃).
• A secondary hydrogen is a hydrogen that is attached to a secondary carbon (-CH₂), so the structure becomes as shown below.

Draw the structure

The name of the structure is n-pentane or normal pentane.

Step-by-step solution

a) Step 1: Selection of chain

Because pentane is the name of the parent hydrocarbon with the molecular formula the longest continuous chain has 5 carbons. Now, draw and number the parent hydrocarbon.

Determine substituents

Now, arrange the parentcarbon in such a way so that contains only primary and secondary hydrogen.

• A primary hydrogen is a hydrogen that is attached to a primary carbon (-CH₃).
• A secondary hydrogen is a hydrogen that is attached to a secondary carbon (-CH₂), so the structure becomes as shown below.

Draw the structure

The name of the structure is n-pentane or normal pentane.

b) : Selection of chain

Because pentane is the name of the parent hydrocarbon with the molecular formula C₅H₁₂, the longest continuous chain has 5 carbons. Now, draw and number the parent hydrocarbon.

Determine the substituents

Now, arrange the parent carbon in such a way that contains only primary hydrogens.

• A primary hydrogen is a hydrogen that is attached to a primary carbon (-CH₃).

Draw the structure

The name of the structure is 2,2-dimethylpropane.

c) : Selection of chain

Because pentane is the name of the parent hydrocarbon with the molecular formula C₅H₁₂, the longest continuous chain has 5 carbons. Now, draw and number the parent hydrocarbon.

Determine the substituents

Now, arrange the parent carbon in such a way such that it contains one tertiary hydrogen.

• A tertiary hydrogen is a hydrogen that is attached to a tertiary carbon (-CH).

Draw the structure

The name of the structure is 2-methylbutane.

d)  Selection of chain

Because pentane is the name of the parent hydrocarbon with that molecular formula C₅H₁₂, the longest continuous chain has 5 carbons. Now, draw and number the parent hydrocarbon.

Determine substituents

Now. arrange the parent carbon in such a way such that it contains two secondary hydrogens.

• A secondary hydrogen is a hydrogen that is attached to a secondary carbon(-CH₂), so the structure becomes as shown below.

:Draw the structure

The name of the structure is isoprene or 2-Methylbuta-1,3-diene.