And Markovnikov’s rule

H2S and thiols add to olefins by electrophilic, nucleophilic, or free-radical mechanisms.192 In the absence of initiators the addition to simple olefins is by an electrophilic mechanism, similar to that in 5-4, and Markovnikov s rule is followed. However, this reaction is usually very slow and often cannot be done or requires very severe conditions unless a proton or Lewis acid catalyst is used. For example, the reaction can be performed in concentrated... 

When this reaction takes place with water, a halotn/rfriit is formed and Markovnikov s rule is followed where the electrophile adds to the least substituted carbon. Water acts as the nucleophile in the second step instead of the bromide ion. (A halohydrin is a hydroxyl group and a halogen attached to adjacent carbons.)... 

With an isolated diene, electrophilic addition of one equivalent of HBr yields one product and Markovnikov s rule is followed. The H atom bonds to the less substituted carbon— that is, the carbon atom of the double bond that had more H atoms to begin with. 

I Thirteen Key Ideas are highlighted in the book. I hese include topics pivotal to students development in organic chemistry, such as Curved Arrows in Reaction Mechanisms (Chapter 5) and Markovnikov s Rule (Chapter 6). These Key Ideas are further reinforced in end-of-chapter problems marked with a a icon. A selection of these problems are also assignable in OWL, denoted by a . 

The first step in the mercuric-ion-catalyzed hydration of an alkyne is formation of a cyclic mercurinium ion. (Two of the electrons in mercury s filled 5d atomic orbital are shown.) This should remind you of the cyclic bromonium and mercurinium ions formed as intermediates in electrophilic addition reactions of alkenes (Sections 4.7 and 4.8). In the second step of the reaction, water attacks the most substituted carbon of the cyclic intermediate (Section 4.8). Oxygen loses a proton to form a mercuric enol, which immediately rearranges to a mercuric ketone. Loss of the mercuric ion forms an enol, which rearranges to a ketone. Notice that the overall addition of water follows both the general rule for electrophilic addition reactions and Markovnikov s rule The electrophile (H in the case of Markovnikov s rule) adds to the sp carbon bonded to the greater number of hydrogens. 

Electrophilic Addition of Hydrogen Halides to Alkenes Mechanism and Markovnikov s Rule 340... 

ELECTROPHILIC ADDITION OF HYDROGEN HALIDES TO ALKENES MECHANISM AND MARKOVNIKOV S RULE... 

Relative Stabilities of Carbocations Regioselectivity and Markovnikov s Rule... 

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