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Organic Chemistry Alkenes / Dienes Alkynes.

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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 C per carbon Hexane b.p. 69 C; 1-Hexene b.p C Heptane b.p. 98 C; 1-Heptene b.p. 93 C

6 Naming Alkenes 1st member is C2H4, ethene. H H C=C
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

7 Alkene Homologous Series (C1-C2 double bond)
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

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

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

12 Dienes 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 Double bonds must all be in the backbone.

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

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 Alkyne Homologous Series (C1-C2 triple bond)
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

16 A common use of one of the alkynes: The Acetylene torch
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 H–CC–C–H C3H4 propyne CHCCH3
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–CC–C–C–H C4H6 1-butyne CHCCH2CH3 H H H–C–CC–C–H C4H6 2-butyne CH3CCCH3

20 Can you name this compound?

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