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Organic Chemistry

Organic Chemistry. Alkenes Alkynes. Mr. Shields Regents Chemistry U16 L03. Alkenes. Like the alkanes, the Alkenes form another homologous hydrocarbon series Each member contains one double covalent bond between two C atoms. So alkenes are unsaturated hydrocarbons .

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Organic Chemistry

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  1. Organic Chemistry • Alkenes • Alkynes Mr. Shields Regents Chemistry U16 L03

  2. Alkenes • Like the alkanes, the Alkenes form another homologous hydrocarbon series • Each member contains one double covalent bond between two C atoms. • So alkenes are unsaturated hydrocarbons. • General formula = CnH2n (2H less than the Alkanes) • What was the general formula for the Alkanes?

  3. Saturated vs Unsaturated

  4. Saturation vs. Unsaturation • Simply put, a saturated hydrocarbon has no double bonds between the Carbon atoms (ex. alkanes) • Unsaturated has one or more double or triple bonds between carbons (alkenes, alkynes)

  5. Physical properties of the Alkenes • Alkenes have properties similar to the alkanes • Insoluble in water • But very soluble in organic solvents • Less dense than water (density of water = 1.0) • B.P. and M.P increase w/ increasing carbon # • Slightly lower than the corresponding alkane • As with alkanes B.P rises about 20-30 C per carbon • Hexane b.p. 69 C; 1-Hexene b.p. 63.5 C • Heptane b.p. 98 C; 1-Heptene b.p. 93 C

  6. Naming Alkenes • Names are derived using the same prefix used to name the alkane chain with the same number of C atoms. • Replace the –ane ending of the alkane name with –ene. 1st member is C2H4, ethene. H H C=C H H Why 1st ?

  7. Naming Alkenes • Location of double bond is specified by numbering C atoms in longest C backbone. Give double bond the lowest possible number. • Do not use a # if there is only 1 possible location 1-butene (not 3) 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 Structural Formula Chemical formula Condensed Structural formula C4H8 CH2CHCH2CH3 C4H8 CH3CHCHCH3

  8. Ethene Propene 1-Butene 1-Pentene 1-Hexene 1-Heptene 1-Octene 1-Nonene 1-Decene C=C C-C=C C-C-C=C C-C-C-C=C C-C-C-C-C=C C-C-C-C-C-C=C C-C-C-C-C-C-C=C C-C-C-C-C-C-C-C=C C-C-C-C-C-C-C-C-C=C Alkene Homologous Series(w/ C1-C2 double bond) What is the name of this alkene? C-C-C=C-C-C-C

  9. Naming Alkenes • Once double bond is numbered specify substituents alphabetically by carbon number • Do not use a number if there is only 1 possible location • Use di, tri and tetra for multiple substituents of the same group 2,3-dimethyl-1-butene C=C–C–C C C Structural Formula (w/o the H) Chemical formula Condensed Structural formula C6H12 CH2C(CH3)CH(CH3)CH3

  10. Draw the following alkenes: 2-Butene methylpropene 4–Methyl–2-pentene 3,3-Dimethyl-1-butene Problems:

  11. Name this Compound: And “E” before “M” 4-ethyl-5-methyl-4-octene (why? What is the longest C chain?

  12. Alkynes • Homologous series of unsaturated hydrocarbons that contain one triple bond. • Each member contains one triple carbon-carbon bond. • Alkynes are unsaturated. • General formula = CnH2n-2

  13. Ethyne Propyne 1-Butyne 1-Pentyne 1-Hexyne 1-Heptyne 1-Octyne 1-Nonyne 1-Decyne C C C-C C C-C-C C C-C-C-C C C-C-C-C-C C C-C-C-C-C-C C C-C-C-C-C-C-C C C-C-C-C-C-C-C-C C C-C-C-C-C-C-C-C-C C Alkyne Homologous Series(w/ C1-C2 triple bond)

  14. Ethyne (Common name) A common use of one of the alkynes: The Acetylene torch What is the IUPAC name for this compound?

  15. Hydrocarbon Table Notice that each Of the hydrocarbon Families differs From the next By 2 hydrogen Alkanes share 1pr e- Alkenes share 2pr e- Alkynes share 3pr e-

  16. Naming Alkynes • Use the corresponding name from the alkane series and change the –ane to –yne. • If necessary, number the carbon atom at which the triple bond occurs with the lowest number. • Use the same naming process you used for naming Alkenes

  17. Structural Chemical Name Condensed Formula Formula Structural formula H–CC–H C2H2 ethyne CHCH H H–CC–C–H C3H4 propyne CHCCH3 H H H H–CC–C–C–H C4H6 1-butyne CHCCH2CH3 H H H H H–C–CC–C–H C4H6 2-butyne CH3CCCH3 H H

  18. Can you name this compound? 3-ethyl-1-pentyne

  19. C C-C-C=C-C-C-C-C C C C C C C Problems Name this alkyne: 5,7-diethyl-3-methyl-4-decyne

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