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Chemistry Question 63 – JEE-MAIN 2026

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IUPAC name of the some alkenes are given below. Find out the correct stability order. A. 2-Methylbut-2-ene B. cis-But-2-ene C. 2, 3-Dimethylbut-2-ene D. Prop-1-ene Choose the correct answer from the options given below :

Alkene stability is primarily determined by the degree of substitution around the double bond. More substituted alkenes are generally more stable.

Step 1: Identify Alkene Structures and Substitution✦ Active

Draw the structural formula for each given alkene and classify its substitution pattern:

A. 2-Methylbut-2-ene: CH3−C(CH3)=CH−CH3 (trisubstituted)

B. cis-But-2-ene: CH3−CH=CH−CH3 (disubstituted)

C. 2, 3-Dimethylbut-2-ene: (CH3)2C=C(CH3)2 (tetrasubstituted)

D. Prop-1-ene: CH2=CH−CH3 (monosubstituted)

Step 2: Count Alpha-Hydrogens○ Expand

Determine the number of alpha-hydrogens for each alkene. Alpha-hydrogens are hydrogens on carbons directly attached to the double bond carbons:

A. 2-Methylbut-2-ene: 9 alpha-H (3 from CH3 on C2, 3 from CH3 on C3, 3 from CH3 on C4)

B. cis-But-2-ene: 6 alpha-H (3 from CH3 on C1, 3 from CH3 on C4)

C. 2, 3-Dimethylbut-2-ene: 12 alpha-H (3 from each of the four methyl groups)

D. Prop-1-ene: 3 alpha-H (3 from CH3 on C3)

💡 Teacher's Secret Hint

Remember that alpha-hydrogens are on carbons adjacent to the double bond, not directly on the double bond carbons themselves.

Step 3: Determine Stability Order○ Expand

Alkene stability increases with the number of alpha-hydrogens due to hyperconjugation. Therefore, the stability order is:

C(12 alpha-H)>A(9 alpha-H)>B(6 alpha-H)>D(3 alpha-H)

This corresponds to option 1.

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