Chemistry Hydrocarbons MDCAT 2014
PMDC Verified Question 54 of 65
Addition of unsymmetrical reagent to an unsymmetrical alkene is governed by:
A
Cannizzaro's Reaction
B
Aldol condensation
C
Krichoff Rule
D
Markownikov's Rule
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Markownikov's Rule
Concept:

Regioselectivity in the electrophilic addition of alkenes is guided by the stability of the intermediate carbocation.

Solution:

  • When an unsymmetrical reagent (like HX) adds to an unsymmetrical alkene, the reaction strictly follows Markovnikov's rule.


  • The rule states that the positive part of the reagent (usually \( \text{H}^+ \)) attaches to the double-bonded carbon bearing the greater number of hydrogen atoms.


  • This ensures the formation of the most highly substituted, and thus most stable, intermediate carbocation.


Why other options are incorrect:

  • Cannizzaro and Aldol reactions are specific to aldehydes/ketones, not alkenes.


  • Kirchhoff's rules govern electrical circuits and thermodynamics, not organic reaction regiochemistry.

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