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Alkenes

Alkenes. Alkanes: C n H 2 n +2 saturated hydrocarbons Alkenes: C n H 2 n unsaturated hydrocarbons. propene (propylene). 2-methylpropene (isobutylene). ethene (ethylene). a -pinene (turpentine). chloroethene (vinyl chloride). oleic acid (a monounsaturated fatty acid). Nomenclature.

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Alkenes

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  1. Alkenes

  2. Alkanes: CnH2n+2saturated hydrocarbons Alkenes: CnH2nunsaturated hydrocarbons propene (propylene) 2-methylpropene (isobutylene) ethene (ethylene) a-pinene (turpentine) chloroethene (vinyl chloride) oleic acid (a monounsaturated fatty acid)

  3. Nomenclature • alkenes: parent chain contains C=C • C=C gets lowest numbers • position of C=C indicated by lower of the two numbers 1-butene 4-methyl-1-butene 3-bromocyclohexene

  4. Nomenclature • polyenes: alkadiene, alkatriene, etc. 1,3-butadiene 5,5-dimethyl-1,3-cyclopentadiene bicyclo[2.2.1]-2,5-heptadiene

  5. Nomenclature • C=C and OH: alkenol higher priority group (OH) gets last suffix and lowest number 2-propen-1-ol 5-methyl-4-hexen-2-ol 2-cyclohexenol

  6. Nomenclature • as side groups: Examples vinyl chloride allyl alcohol isopropenyl bromide ethenyl (vinyl) 2-propenyl (allyl) 1-methylethenyl (isopropenyl) methylene 1-vinylcyclohexene methylenecyclopentane

  7. Nomenclature Question. Give IUPAC names for the following compounds. To check your answers, click on the arrow.

  8. Nomenclature Geometric isomers: cis and trans geometric isomers cis-2-butene trans-2-butene

  9. Nomenclature Geometric isomers: cis and trans cis trans cis cis, trans

  10. cis, trans?? Nomenclature E-Z notation The cis and trans designations apply only when there are two groups.

  11. Nomenclature E-Z notation • Determine the higher priority group on each end of the alkene. • If the higher priority groups are: • on opposite sides: E (entgegen = opposite) • on the same side: Z (zusammen = together) CH3 > H Cl > CH2CH3 (E)-3-chloro-2-pentene (Z)-3-chloro-2-pentene

  12. Nomenclature E-Z notation • Priority Rules: • look at the first atom attached to the alkene carbon • higher atomic number = higher priority • if same atomic number, higher atomic mass = higher priority (e.g., D > H, 13C > 12C, etc.) • if atoms are identical, examine next atoms along chain and apply rules 2 and 3. (H,H,H) (C,H,H) (C,C,H) (C,C,C) (Cl,H,H) Look for higher atomic number at first point of difference.

  13. Nomenclature E-Z notation • Priority Rules: • multiple bonds: treat each p bond as if it were another single bond to that type of atom

  14. Nomenclature Question. Designate each double bond as E or Z, where applicable. Click on the arrow to check your answers. geraniol

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