Organic chemistry for medicine and biology students

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• Organic chemistry for medicine and biology
  students
• Chem 2311
• Chapter 3
• Alkenes and Alkynes
• By Prof. Dr.
• Adel M. Awadallah
• Islamic University of Gaza

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• Alkenes and Alkynes
• Hydrocarbons (contain only carbon and hydrogen)
• Saturated (Contain only single bonds)
• Alkanes (CnH2N 2 )
• Cycloalkanes (CnH2N )
• b) Unsaturated contain
• Alkenes double bonds (,,,CnH2N)
• Alkynes triple bonds ((CnH2N - 2)
• Aromatic benzene like compounds

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Facts about double and triple bonds
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• Nomenclature of alkenes and Alkynes
• The ending ene is used for alkenes and yne for
  alkynes
• Select the longest chain that includes both
  carbons of the multiple bond
• Number the chain from the end nearest to the
  multiple bond
• Indicate the position of the multiple.
• Examples

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Isomers and common names of simple alkenes
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Assigning Priority

• Alkenes and alkynes are considered to have equal
  priority
• In a molecule with both a double and a triple
  bond, whichever is closer to the end of the chain
  determines the direction of numbering.
• In the case where each would have the same
  position number, the double bond takes the lower
  number.
• In the name, ene comes before yne because of
  alphabetization.

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Compounds containing more than one double bond
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• Cis-Trans (Z-E) Isomerism in Alkenes
• If each end of the double bond is attached to
  two different groups, then the compound exists in
  two different forms called (Diastereomers These
  are non mirror image stereoisomers).
• If the two groups are identical we distinguish
  the two isomers by adding the prefix cis (same
  side) or trans (opposite sides)
• Example

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• If the groups attached to the double bond are
  different, we distinguish the two isomers by
  adding the prefix Z (same side) or E (opposite
  sides) depending on the atomic number of the
  atoms attached to each end of the double bond

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Hydrogen is a symmetric reagent
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Bromine is a symmetric reagent
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Water is unsymmetric reagent
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• Addition of HBr (Unsymmetric reagent)

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