# anti markovnikov rule with example

Markovnikov’s Rule. Anti markovnikovs rule When hydrogen halide is added to the unsymmetrical alkenes ,it results in the formation of alkyl halide provided that hydrogen attached to the carbon atom having less no. The proton adds first to the carbon-carbon double bond. Similarly, the addition reaction that follows the Markownikoff rule is referred to as the Markownikoff addition. These OH radicals will go on and attack HBr, which will take the Hydrogen and create a Bromine radical. This process is quite unusual, as carboncations which are commonly formed during alkene, or alkyne reactions tend to favor the more substitued carbon. [ "article:topic", "showtoc:no", "license:ccbyncnd", "transcluded:yes", "source[1]-chem-892" ], 5.13: Homolytic Cleavage and Bond Dissociation Energies, http://uncyclopedia.wikia.com/wiki/Organic_chemistry, http://uncyclopedia.wikia.com/wiki/Chemistry, K. Peter C. Vollhardt, Neil E. Schore; Organic Chemistry: Structure and Function Fifth Edition; W. H. Freeman and Campany, 2007, Micheal Vokin; Nuffield Advance Chemistry Student's Book Forth Edition; Person Education Limited, 2004, $$\ce{CH_3-C(CH3)=CH-CH_3 + HBr + H_2O_2 \rightarrow}$$, $$\ce{CH_3C(CH_3)=CH-CH_3 + HI + H_2O_2 \rightarrow }$$, $$\ce{CH_3C(CH_3)=CH-CH_3 + HCl + H_2O_2 \rightarrow }$$, $$\ce{CH_3CH=CH-CH3 + HBr + H_2O_2 \rightarrow }$$, $$\ce{CH_3C(CH_3)=CH-CH_3 + HBr \rightarrow }$$. This radical addition of bromine to alkene by radical addition reaction will go on until all the alkene turns into bromoalkane, and this process will take some time to finish. This is known as Markovnikov's Rule. In the absence of peroxides, hydrogen bromide adds to propene via an electrophilic addition mechanism. Some reactions do not follow Markovnikov's Rule, and anti-Markovnikov products are isolated. The Bromine Radical will go on and attack the LESS SUBSTITUTED carbon of the alkene. There are also Termination Steps, but we do not concern about the termination steps as they are just the radicals combining to create waste products. Watch the recordings here on Youtube! To demonstrate the anti-Markovnikov regiochemistry, I will use 2-Methylprop-1-ene as an example below: Hydrogen Peroxide is an unstable molecule, if we heat it, or shine it with sunlight, two free radicals of OH will be formed. Several reactions have been discussed, which follow this rule. Have questions or comments? Anti - Markovnikov addition of hydrogen bromide to propene , illustrating the peroxide effect . HI and HCl cannot be used in radical reactions, because in their radical reaction one of the radical reaction steps: Initiation is Endothermic, as recalled from Chem 118A, this means the reaction is unfavorable. Anti-Markovnikov addition of HBr to alkenes We saw in section 10.4 that under normal conditions, HBr adds to an unsymmetrical alkene to form an alkyl halide where the H goes onto the less substituted carbon, and the Br goes onto the more substituted carbon – thus, it obeys Markovnikov’s Rule. The 'anti' in 'anti-Markovnikov' refers to the fact the reaction does not follow Markovnikov's rule, instead of being a reference to anti addition stereochemistry. For example two bromine radical combined to give bromine. A carbon radical is more stable when it is at a more substituted carbon due to induction and hyperconjugation. Anti-Markovnikov rule describes the regiochemistry where the substituent is bonded to a less substituted carbon, rather than the more substitued carbon. Anti-Markovnikov Radical Addition of Haloalkane can ONLY happen to HBr and there MUST be presence of Hydrogen Peroxide (H2O2). Anti-Markovnikov rule describes the regiochemistry where the substituent is bonded to a less substituted carbon, rather than the more substitued carbon. It is one of the few reactions following free radical mechanism in organic chemistry in place of electrophilic addition as suggested by Markovnikov. The more stable free radical (3° > 2° > 1°) defines the orientation of halogen. Anti-Markovnikov Rule. Anti-Markovnikov rule describes the regiochemistry where the substituent is bonded to a less substituted carbon, rather than the more substitued carbon. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. 10.8.1. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Hydrogen Peroxide is essential for this process, as it is the chemical which starts off the chain reaction in the initiation step. Examples: Mechanism: It’s a free radical addition reaction and involves the formation of free radical. Markovnikov vs Anti Markovnikov Rule: Markovnikov Rule explains when the addition of protic acid with the formula of HX (where X= halogen) or H 2 O (considered as H-OH) to an alkene, hydrogen attaches to the double bonded carbon with the greater number of hydrogen atoms, while the halogen (X) attaches to the other carbon. This is because after the bromine radical attacked the alkene a carbon radical will be formed. For example: Tertiary carbon (most substituted), Secondary carbon (medium substituted), primary carbon (least substituted). This process is quite unusual, as carboncations which are commonly formed during alkene, or alkyne reactions tend to favor the more substitued carbon.