The chemical reactions at the place of the destruction of the double bond in alkenes and triple in the alkyne can join various particles.How is subject to the laws of this process?To investigate the behavior of asymmetrical homologues of ethylene at gidrogalogenirovanii and hydration Russian scientist VV Markovnikov.He found that the reaction mechanism depends on how the number of hydrogen with carbon connected with a double bond.The hypothesis put forward by a scientist, confirmed after the discoveries in the field of atomic structure.Markovnikov's rule has laid the basis for the creation of a scientific theory with practical application.It allows you to more efficiently organize the production of polymers, lubricants, alcohols.
Markovnikov's rule
Russian scientist in the activity devoted much time to the study of the mechanism of attachment of asymmetric reagents to unsaturated hydrocarbons.In his article, published in German in 1870, VV Markovnikov drew the attention of the scientific community on a selective interaction of hydrogen halides with carbon atoms located at the double bond in unsymmetrical alkenes.Russian researcher cited data that it has received experimentally in the laboratory.Markovnikov wrote that halogen necessarily joined to the carbon atom that contains the least number of hydrogen atoms.Most popular scientific works acquired at the beginning of the XX century.He proposed the hypothesis of the mechanism of interaction is called "Markovnikov's rule."
life and work of the scientist-organic
Vladimir Markovnikov was born 25 (13 under Art. Style) in December 1837.He studied at the University of Kazan, and later taught at this school and the University of Moscow.Markovnikov studied the behavior of unsaturated hydrocarbons by reaction with hydrogen halides since 1864.Until 1899, scientists in other countries paid no attention to the conclusions of the Russian chemist.Markovnikov, except rule, the name in his honor, made a number of other discoveries:
- got cyclobutanedicarboxylic acid;
- investigated the oil of the Caucasus and opened it a special composition of organic matter - naphtha;
- set the difference in the melting points of compounds with straight and branched chain;
- proved fatty acid isomers.
Proceedings scientist contributed significantly to the development of the domestic chemical science and industry.
essence of the hypothesis put forward by Markovnikov
scientist spent many years studying the reactions of addition of reagents to unsaturated hydrocarbons with one double bond (alkenes).It is noted that if the composition of the compounds in the presence of hydrogen, it is directed to the carbon atom, which contains more particles of that species.Anion attached to adjacent carbon.This is a rule Markovnikov its essence.Scientific genius to predict the behavior of particles on the structure of which at that time were not very clear.In accordance with the rule of ethylene hydrocarbons to join complex substances that are part of the HX, where X:
- halogen;
- hydroxyl;
- acidic residue of sulfuric acid;
- other particles.
modern sound Markovnikov rule differs from the language of the scientist: a hydrogen atom of a molecule HX connectable alkene is directed to carbon double bond, which already contains more hydrogen and the particle X is sent to the least hydrogenated atom.
attachment mechanism of electrophilic particles
Consider the kinds of chemical reactions in which the rule applies Markovnikov.Examples:
- addition reaction of hydrogen chloride to propene.During the interaction between the particles is the destruction of the double bond.Anion of chlorine goes to the less hydrogenated carbon, located at the double bond.Hydrogen reacts with most of these hydrogenated atoms.Formed 2-chloro propane.
- The addition reaction of the hydroxyl molecules of water suitable for its composition less than hydrogenated carbon.Hydrogen joins the most hydrogenated atom at the double bond.
There are exceptions to the Markovnikov rule proposed in those reactions where the reactants are the alkenes, in which the carbon in the double bond already has a number of electronegative group.It selects partially electron density, which is usually attracted to the positively charged hydrogen.Do not follow the rules and in the reactions going on the radical rather than electrophilic mechanism (Harish effect).These exceptions do not detract from the merits of the rules derived prominent Russian organic chemist Vladimir Markovnikov.
