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Organic Chemistry

Organic Chemistry. Alkenes / Dienes Alkynes. Alkenes. The Alkenes form another homologous hydrocarbon series Each member contains one double covalent bond between two C atoms. So alkenes are said to be unsaturated . Only 3 atoms joined to each C, not 4 General formula = C n H 2n

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Organic Chemistry

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  1. Organic Chemistry • Alkenes / Dienes • Alkynes

  2. Alkenes • The Alkenes form another homologous hydrocarbon series • Each member contains one double covalent bond between two C atoms. • So alkenes are said to be unsaturated. • Only 3 atoms joined to each C, not 4 • General formula = CnH2n • 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 • Very similar to the alkanes • Insoluble in water • very soluble in organic solvents • Less dense than water • B.P. and M.P increase with increasing carbon • 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 from the name of 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

  7. 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(C1-C2 double bond)

  8. Naming Alkenes • Location of double bond is specified by numbering C atoms in backbone. Give bond the lowest possible number. 1-butene (not 4) 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

  9. Naming Alkenes • Once double bond is numbered specify substituents alphabetically by number • 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 2–methylpropene 4–Methyl–2-pentene 3,3-Dimethyl-1-butene Problems:

  11. Name this Compound: 4-ethyl-5-methyl-4-octene

  12. Alkenes = 1 double bond Dienes have 2 double bonds End in -diene Location still denoted by numbers Determine which way to number the C backbone by assigning the lowest possible number to one of the double bonds Example: 1,3 – pentadiene c=c-c=c-c Not 2,4-pentadiene Substituents are named first [Numbers are separated by commas and the #’s are Separated from the name by a dash Dienes Double bonds must all be in the backbone.

  13. C=C-C=C-C-C-C C Name this compound: C=C-C-C-C=C-C C 5-methyl-1,5-heptadiene Draw 2-methyl-1,3-heptadiene:

  14. 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

  15. 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(C1-C2 triple bond)

  16. Ethene (Common name) A common use of one of the alkynes: The Acetylene torch

  17. 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- Can you explain how The above comments Are related?

  18. 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

  19. 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

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

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