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4: Introduction to Alkenes

  • Page ID
    • 4.1: The \(\pi\) Bond
      Molecular orbital description of the alkene double bond
    • 4.2: Nomenclature of Alkenes
      Alkenes and alkynes are hydrocarbons which respectively have carbon-carbon double bond and carbon-carbon triple bond functional groups. The molecular formulas of these unsaturated hydrocarbons reflect the multiple bonding of the functional groups. Alkenes are named as if they were alkanes, but the "-ane" suffix is changed to "-ene". If the alkene contains only one double bond and that double bond is terminal then it is not necessary to place any number in front of the name.
    • 4.3: Degree of Unsaturation
    • 4.4: Electrophilic Addition Reactions of Alkenes
      This page looks at the reaction of the carbon-carbon double bond in alkenes such as ethene with hydrogen halides such as hydrogen chloride and hydrogen bromide. Symmetrical alkenes (like ethene or but-2-ene) are dealt with first. These are alkenes where identical groups are attached to each end of the carbon-carbon double bond.
    • 4.5: Carbocation Structure and Stability
      It is a general principle in chemistry that the more a charge is dispersed, the more stable is the species carrying the charge. Put simply, a species in which a positive charge is shared between two atoms would be more stable than a similar species in which the charge is borne wholly by a single atom.
    • 4.6: Carbocation Rearrangements
      Earlier in this chapter we introduced the so-called 'Markovnikov rule', which can be used to predict the favored regiochemical outcome of electrophilic additions to asymmetric alkenes. According to what we have learned, addition of HBr to 3-methyl-1-butene should result in a secondary bromoalkane.
    • 4.7: Markovnikov Addition
      Markovnikov addition, also called Markovnikov's rule, states that a protic acid (HX) will add to an alkene such that the proton will bond to the less substituted carbon.

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