Preferred Label : Markownikoff rule;
IUPAC definition : 'In the addition of hydrogen halides to unsymmetrically constituted [unsaturated]
hydrocarbons, the halogen atom becomes attached to the carbon bearing the lesser number
of hydrogen atoms.' Originally formulated by Markownikoff (Markovnikov) to generalize
the orientation in additions of hydrogen halides to simple alkenes, this rule has
been extended to polar addition reactions as follows. 'In the heterolytic addition
of a polar molecule to an alkene or alkyne, the more electronegative (nucleophilic)
atom (or part) of the polar molecule becomes attached to the carbon atom bearing the
smaller number of hydrogen atoms.' This is an indirect statement of the common mechanistic
observation, that the more electropositive (electrophilic) atom (or part) of the polar
molecule becomes attached to the end of the multiple bond that would result in the
more stable carbenium ion (whether or not a carbenium ion is actually formed as a
reaction intermediate in the addition reactions). Addition in the opposite sense is
commonly called 'anti-Markovnikov addition'.;
Origin ID : M03707;
See also
'In the addition of hydrogen halides to unsymmetrically constituted [unsaturated]
hydrocarbons, the halogen atom becomes attached to the carbon bearing the lesser number
of hydrogen atoms.' Originally formulated by Markownikoff (Markovnikov) to generalize
the orientation in additions of hydrogen halides to simple alkenes, this rule has
been extended to polar addition reactions as follows. 'In the heterolytic addition
of a polar molecule to an alkene or alkyne, the more electronegative (nucleophilic)
atom (or part) of the polar molecule becomes attached to the carbon atom bearing the
smaller number of hydrogen atoms.' This is an indirect statement of the common mechanistic
observation, that the more electropositive (electrophilic) atom (or part) of the polar
molecule becomes attached to the end of the multiple bond that would result in the
more stable carbenium ion (whether or not a carbenium ion is actually formed as a
reaction intermediate in the addition reactions). Addition in the opposite sense is
commonly called 'anti-Markovnikov addition'.
