Markovnikov’s Rule
what is it ?
While adding , an , unsymmetrical reagent such as HCl,Where H+ is the electrophile,and Cl- is the nucleophile , to an unsymmetrical double bond ,
the major product in each case is always the one where the electrophile (hydrogen) adds to the carbon in the double bond with the most hydrogens, and the nucleophile(chlorine) adds to the carbon with the fewest hydrogens.
you can see that in each case, we’re breaking C-C (π) and
forming a new C-H and C-Cl bond. But ,
The major product in each case is always the one where
the hydrogen adds to the carbon with the most hydrogens, and the chlorine adds
to the carbon with the fewest hydrogens.
In other words, this reaction is REGIOSELECTIVE
To describe this, the term
“most substituted” is often thrown around a lot, so here is a graphical
explanation:
REGIOSELECTIVE ????????
If more than one reaction could occur between a set of
reactants under the same conditions giving products that
are constitutional isomers and if one product forms in greater
amounts(MAJOR PRODUCT) than the others(MINOR
PRODUCT), the overall reaction is said to be regioselective.
This empirical observation was
first pointed out in 1870 by one Vladimir Markovnikov and this pattern of
regioselectivity has become known as “Markovnikov’s rule”:
“when an unsymmetrical alkene reacts with a hydrogen halide
to give an alkyl halide, the hydrogen adds to the carbon that has the greater
number of hydrogen substituents, and the halogen to the carbon having the fewer
number of hydrogen substituents”
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