{"id":7249,"date":"2013-04-25T08:23:54","date_gmt":"2013-04-25T12:23:54","guid":{"rendered":"https:\/\/www.masterorganicchemistry.com\/?p=7249"},"modified":"2026-05-06T19:33:06","modified_gmt":"2026-05-07T00:33:06","slug":"summary-alkene-reaction-pathways","status":"publish","type":"post","link":"https:\/\/www.masterorganicchemistry.com\/2013\/04\/25\/summary-alkene-reaction-pathways\/","title":{"rendered":"Summary: Three Key Families Of Alkene Reaction Mechanisms"},"content":{"rendered":"

The Three Key Families Of Alkene Addition Reaction Mechanisms (Plus Two Minor Ones)<\/strong><\/p>\n

In this post we’ll do a final review of alkene addition reactions and sum up the three major families of mechanisms (and two minor classes of reactions worth paying attention to).<\/p>\n

Table of Contents<\/strong><\/p>\n

    \n
  1. Reaction Family #1: The Carbocation Pathway<\/a><\/li>\n
  2. Reaction Family #2: The “3-Membered Ring” Pathway<\/a><\/li>\n
  3. Reaction Family #3: The “Concerted” Pathway<\/a><\/li>\n
  4. Two Miscellaneous Minor Pathways: Oxidative Cleavage of Alkenes And Free-Radical Addition To Alkenes<\/a><\/li>\n
  5. Notes<\/a><\/li>\n
  6. Quiz Yourself!\u00a0<\/a><\/li>\n<\/ol>\n
    \n

    <\/a>1. Alkene Reaction Family #1 – The Carbocation Pathway<\/strong><\/h2>\n

    In the Carbocation Pathway<\/a>, the alkene acts as a nucleophile and attacks an electrophile, resulting in the formation of a carbocation. The regioselectivity is Markovnikov and the stereochemistry of the reaction is a mixture of syn and anti products. Since carbocations are formed, be alert for rearrangements<\/a> ! This is the only family where this can happen.<\/p>\n

    \"carbocation<\/p>\n

    <\/a>2. Alkene Reaction Family #2 – The 3-Membered Ring Pathway<\/strong><\/h2>\n

    In the so called \u00a0“3-membered ring pathway<\/a>” the alkene attacks an electrophile and forms a 3-membered ring intermediate. This intermediate is then attacked at the most substituted carbon by a nucleophile via a backside attack, giving rise to anti stereochemistry:<\/p>\n

    \"3<\/p>\n

    <\/a>3. Alkene Reaction Family #3 – The Concerted Pathway<\/strong><\/h2>\n

    The “concerted” pathway<\/a> is not meant to describe a single reaction mechanism, but it does describe similar consequences. In this class of reaction the regioselectivity is generally not relevant (except for hydroboration with BH3<\/sub>, which is anti-Markovnikov). The stereochemistry of the reaction is syn, meaning the two new bonds form on the same face of the alkene.<\/p>\n

    \"concerted<\/p>\n

    <\/a>4. Two Miscellaneous Minor Alkene Reaction Families: Oxidative Cleavage of Alkenes And Free-Radical Addition To Alkenes<\/strong><\/h2>\n

    In addition there is a fourth pathway which goes through a free radical addition of HBr in the presence of peroxides<\/a>. The regiochemistry is anti-Markovnikov and the stereochemistry is a mixture of syn and anti.<\/p>\n

    Finally in the presence of strong oxidants such as KMnO4<\/sub> or O3<\/sub> alkenes undergo a reaction called oxidative cleavage<\/a> which results in the complete breakage of C=C to form carbonyl compounds.<\/p>\n

    \"two<\/p>\n

    This sums up the series on alkenes for now. In the next series, we’ll go through the reactions of alkynes.<\/p>\n

    Reaction Map – Reactions Of Alkenes<\/a><\/strong><\/p>\n

    \n

    <\/a>Notes<\/strong><\/h2>\n

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