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Unsaturated Hydrocarbons

Unsaturated Hydrocarbons. Double and Triple bonds between Carbons. Objectives. To distinguish between the unsaturated hydrocarbons called alkenes and alkynes and recognize how they differ from alkanes To draw structural diagrams and write structural formulae of alkenes and alkynes

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Unsaturated Hydrocarbons

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  1. Unsaturated Hydrocarbons • Double and Triple bonds between Carbons

  2. Objectives • To distinguish between the unsaturated hydrocarbons called alkenes and alkynes and recognize how they differ from alkanes • To draw structural diagrams and write structural formulae of alkenes and alkynes • To name unsaturated hydrocarbons • To identify the molecular geometry of alkenes and alkynes

  3. Review • Alkanes are saturated hydrocarbons • Saturated hydrocarbons have only single bonds • Examples of alkanes include methane, ethane, propane, 2,3-diethyloctane... • We use system of prefixes to name alkanes

  4. Review

  5. Review • Name based on longest chain of carbons • Use digits to indicate location of carbon attached to substituents • For example: 5-ethyl-3- methylheptane

  6. How to tell from formula if saturated • In a saturated compound, noncyclic hydrocarbon, the molecular formula will have the form CnHn+2 • For example: • C2H6 • C8H18 • C20H42

  7. Alkenes • Unsaturated hydrocarbons that contain one or more double covalent bonds • Simplest alkene has twocarbons joined by a double bond • Ethene • CH2=CH2

  8. Alkenes with More Carbons • Propene • CH2=CH-CH3

  9. Alkenes with More Carbons • Butene • CH2=CH-CH2-CH3 & CH3-CH=CH-CH3

  10. Alkenes with More Carbons • Pentene

  11. Alkene with Substituents • Same basic rules as for alkanes

  12. Alkene with Substituents • 5, 5 - diethyl - 2, 6, 7- trimethyl - 3 - octene

  13. Alkene with more than one double bond • 1, 3 - butadiene

  14. Alkene with more than one double bond • 6-methyl-1,4,8-nonatriene

  15. Alkynes • Unsaturated hydrocarbons that contain one or more triple covalent bonds • Same naming conventions as alkanes and alkenes

  16. Alkynes with More Than 2 Carbons • Propyne • CH≡C-CH3

  17. Alkynes with More Than 2 Carbons • Use initial digit to indicate where triple bond is • e.g. 1-hexyne, CH≡C-CH2-CH2-CH2-CH3 • 2-hexyneCH3-C≡C-CH2-CH2 -CH3 • 3-hexyneCH3-CH2-C≡C-CH2-CH3

  18. Alkynes with Substituents • 7-methyl-3-octyne • CH3-CH-CH2-CH2-C≡C-CH2-CH3|CH3

  19. VSEPR Geometry - Unsaturated Hydrocarbons • Carbon with 1 double bond and two single bonds: three groups/regions of electrons around it • Trigonal planar geometry

  20. VSEPR Geometry - Unsaturated Hydrocarbons • Carbon with 2 double bonds: two groups/regions of electrons around it • Linear geometry

  21. VSEPR Geometry - Unsaturated Hydrocarbons • Carbon with 1 double bonds and 1 single bond: two groups/regions of electrons around it • Linear geometry

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