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Alkenes C n H 2n

Alkenes C n H 2n. Alkenes. 2 nd homologous series hydrocarbons Each contains one double covalent bond  So alkenes are unsaturated General formula = C n H 2n. 1 st member is C 2 H 4 , ethene H H C =C H H. Naming Alkenes.

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Alkenes C n H 2n

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  1. Alkenes CnH2n

  2. Alkenes • 2nd homologous series hydrocarbons • Each contains one double covalent bond So alkenes are unsaturated • General formula = CnH2n

  3. 1st member is C2H4, ethene H H C=C H H Naming Alkenes • Find longest # of C’s = parent chain • Suffix = -ene

  4. Alkenes with 4 or more C’s • Use lowest possible # to specify location of 1st C in double bond

  5. 2-butene H H H C=C–C–C–H H H H H H H H H H–C–C=C–C–H H H C4H8 CH2CHCH2CH3 C4H8 CH3CHCHCH3 Naming Alkenes • Prefix = C atoms in backbone • doublebond given lowest possible # 1-butene

  6. Naming Branched-Chain Alkenes • Parent chain = longest chain that contains double bond • position of double bond (not branches) determines numbering of backbone • Give 1st C in bond lowest possible #

  7. Properties of Alkenes • Nonpolar – low solubility in H2O • low mp & bp • More reactive than alkanes • double bond = site of reactivity

  8. Alkynes CnH2n-2

  9. Alkynes • Homologous series unsaturatedhydrocarbons that contain one triple bond • Each contains one triple C to C bond • Alkynes are unsaturated • General formula = CnH2n-2

  10. Naming Alkynes Name: Prefix depends on # C’s Suffix = -yne number 1st carbon atom at which triple bond occurs

  11. H–CC–H C2H2ethyneCHCH H H–CC–C–H H propyne C3H4 CHCCH3 1-butyne C4H6 CHCCH2CH3 C4H6 2-butyne CH3CCCH3 H H H–CC–C–C–H H H H H H–C–CC–C–H H H

  12. Name of Series General Formula Ending Alkanes CnH2n+2 -ane Alkenes CnH2n -ene Alkynes CnH2n-2 -yne 3 Homologous Series of HC’s

  13. Which compound belongs to the alkene series? • C2H2 • C2H4 • C6H6 • C6H14 Correct answer = B -Alkenes follow the format CnH2n - A & C are CnHn - D is CnH2n+2

  14. In which group could the hydrocarbons all belong to the same homologous series? • C2H2, C2H4, C2H6 • C2H4, C3H4, C4H8 • C2H4, C2H6, C3H6 • C2H4, C3H6, C4H8 Correct answer = D -Members of homologous series all have same relationship between atoms - Every compound in D fits formula CnH2n

  15. Which of the following is a saturated hydrocarbon? • Ethene • Ethyne • Propene • Propane Correct answer = D - alkanes are saturated

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