6.5 Regioselectivity of Hydrogen Halide Addition: Markovnikov's Rule RCH=CH+H一X—> RCH-CH, rather than RCh-CH H X R2C=CH2+H一x→>R2C一CH2 rather than r2C一CH R,C=CHR +H-X->R,C-CHR rather than R,C-CHR In 1870, Vladimir Markovnikov, a colleague of Alexander Zaitsev at the univer- sity of Kazan, noticed a pattern in the hydrogen halide addition to alkenes and assem- 1988 issue of the Journal of bled his observations into a simple statement. Markovnikov's rule states that when an Chemical Education trace velopment of unsymmetrically substituted alkene reacts with a hydrogen halide, the hydrogen adds to Markoynikoy's rule In that the carbon that has the greater number of hydrogen substituents, and the halogen adds article Markovnikov's name to the carbon having fewer hydrogen substituents. The preceding general equations illus- is spelled Markownikoft, trate regioselective addition according to Markovnikov's rule, and the equations that fol- which is the way it appeared low provide some examples CH3 CH,CH-CH2 HBr >CHaCH,CHCH 1-Butene Hydrogen bromide 2-Bromobutane(80%) CH2-C-B C CH3 2-Methylpropene Hydrogen bromide 2-Bromo-2-methylpropane (90%0) CH HCI 1-Methylcyclopentene Hydrogen chloride 1-Chloro-1-methylcyclopentane (100%0) PROBLEM 6.3 Write the structure of the major organic product formed in the reaction of hydrogen chloride with each of the following (a)2-Methyl-2-butene (c cis-2-Butene (b)2-Methyl-1-butene CH3CH SAMPLE SOLUTION (a)Hydrogen chloride adds to the double bond of 2 methyl-2-butene in accordance with Markovnikov's rule. The proton adds to the carbon that has one attached hydrogen, chlorine to the carbon that has none Back Forward Main MenuToc Study Guide ToC Student o MHHE WebsiteIn 1870, Vladimir Markovnikov, a colleague of Alexander Zaitsev at the Univer￾sity of Kazan, noticed a pattern in the hydrogen halide addition to alkenes and assem￾bled his observations into a simple statement. Markovnikov’s rule states that when an unsymmetrically substituted alkene reacts with a hydrogen halide, the hydrogen adds to the carbon that has the greater number of hydrogen substituents, and the halogen adds to the carbon having fewer hydrogen substituents. The preceding general equations illus￾trate regioselective addition according to Markovnikov’s rule, and the equations that fol￾low provide some examples. PROBLEM 6.3 Write the structure of the major organic product formed in the reaction of hydrogen chloride with each of the following: (a) 2-Methyl-2-butene (c) cis-2-Butene (b) 2-Methyl-1-butene (d) SAMPLE SOLUTION (a) Hydrogen chloride adds to the double bond of 2- methyl-2-butene in accordance with Markovnikov’s rule. The proton adds to the carbon that has one attached hydrogen, chlorine to the carbon that has none. CH3CH CH3 1-Methylcyclopentene  HCl Hydrogen chloride CH3 Cl 1-Chloro-1-methylcyclopentane (100%) 0°C C H3C H3C CH2 2-Methylpropene  HBr Hydrogen bromide CH3 C Br CH3 CH3 2-Bromo-2-methylpropane (90%) acetic acid  Hydrogen bromide HBr 2-Bromobutane (80%) CH3CH2CHCH3 Br 1-Butene CH3CH2CH CH2 acetic acid RCHœCH2  H±X RCH±CH2 W X W H RCH±CH2 W H W X rather than R2CœCH2  H±X R2C±CH2 W X W H R2C±CH2 W H W X rather than R2CœCHR H  ±X R2C±CHR W X W H R2C±CHR W H W X rather than 6.5 Regioselectivity of Hydrogen Halide Addition: Markovnikov’s Rule 215 An article in the December 1988 issue of the Journal of Chemical Education traces the historical development of Markovnikov’s rule. In that article Markovnikov’s name is spelled Markownikoff, which is the way it appeared in his original paper written in German. Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website