Q.2 - Organic Chemistry

Question

Classify each alkene in the following vitamins by the number of carbon substituents bonded to the double bond.

a.

b.

Step-by-Step Solution

Answer

• a=tetrasubstituted
• b=disubstituted
• c=trisubstituted
• d= disubstituted
• e= trisubstituted

• a=disubstituted
• b=trisubstituted
• c=trisubstituted

Definition of alkene

An alkene is defined as an unsaturated structure where a double bond is present between two carbon atoms.

They are  ${\text{sp}}^3$ hybridized carbons that impart stability to the system.

Types of alkenes

An alkene can be classified on the number of the substituted alkyl group present instead of hydrogens. 

• When only one alkyl substituent is present, then the alkene is considered to be monosubstituted. 
• When two alkyl substituent is present, then the alkene is considered to be disubstituted. 
• For three alkyl substituents, then the alkene is considered to be trisubstituted. 
• For four alkyl substituents, it is tetrasubstituted.

Finding of the carbons attached to the double-bonded carbons

The carbons that are attached to the double-bonded carbons are observed first. And based on the result, the alkenes can be classified. 

Representation of the number of substituents present across the alkene

Classification based on the number of alkyl substituents present

Numbering of double bonds in a

The double bond marked as (a) is tetrasubstituted since four alkyl substituents are present. For both (c) and (e), three alkyl substituents are present, so they are trisubstituted. 

And for both (b) and (d), two alkyl substituents are present; hence they are considered disubstituted.

Numbering of double bonds in b

The double bond marked as (a) is disubstituted since two alkyl substituents are present. For both (b) and (c), three alkyl substituents are present, so they are trisubstituted.

Based on that, the following alkenes can be classified as follows:

• a=tetrasubstituted
• b=disubstituted
• c=trisubstituted
• d= disubstituted
• e= trisubstituted

• a=disubstituted
• b=trisubstituted
• c=trisubstituted