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Alkenes and Alkynes Contain C-C double and triple bonds General alkene formula C n H 2n

Alkenes and Alkynes Contain C-C double and triple bonds General alkene formula C n H 2n General alkyne formula C n H 2n-2 More reactive than alkanes Known as unsaturated hydrocarbons. H. H. H. C. C. H. Thermal cracking:

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Alkenes and Alkynes Contain C-C double and triple bonds General alkene formula C n H 2n

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  1. Alkenes andAlkynes • ContainC-C double and triple bonds • General alkene formula Cn H2n • General alkyne formula Cn H2n-2 • More reactive than alkanes • Known as unsaturated hydrocarbons H H H C C H

  2. Thermal cracking: • Process of breaking the long chain-alkanes found in petroleum into shorter chain alkanes and alkenes. • Multiple bonds are also formed by removing a • hydrogen chemically – dehydrogenation. C C C C H H H H H H H H C C C C H + H2 H H + H2 H H H H H

  3. Alkenes / Alkynes are converted to alkanes by hydrogenationoraddition reaction.

  4. Naming Alkenes and Alkynes • Find parent chain with the double/triple bond. • Named as total carbons using ending ene / yne • Show the location of the bond by the carbon number separated with a hyphen. (2-pentene) • Number carbons from the end that gives the lowest • number to the double or triple bond. • Name alkyl branches as in alkanes.

  5. ethene CH2= CH2 H H H H H H C ≡ C C = C H H H H ethyne CH ≡ CH C C C C H H

  6. 2-hexene CH3CH=CHCH2CH2CH3 1 2 3 4 5 6 C - C - C - C C - C = 3-hexyne CH3CH2C≡CCH2CH3 1 2 3 4 5 6 C ≡ C - C - C C - C -

  7. 4-methyl-2-pentene (4-methylpent-2-ene) (Note, lowest number goes to the double bond)

  8. CH3CH2CH(CH3)CH=C(C2H5)CH2CH3 7 6 5 4 3 2 1 3-ethyl-5-methyl-3-heptene *Show double/triple bond in condensed formula.

  9. Draw the structural formula for 1-butene. CH2=CH–CH2–CH3 Draw a condensed for 2,5,5-trimethyl-2-hexene. CH3C(CH3)=CHCH2C(CH3)2CH3 3 4 6 1 2 5

  10. HC≡CCH2C(C2H5)2CH2CH(CH3)CH(CH3)CH3 1 2 3 4 5 6 7 8 4,4-diethyl-6,7-dimethyl-1-octyne

  11. Draw a structural of 2,2,5,5-tetramethyl-3-hexyne.

  12. Like Alkyl groups (trimethyl), prefixes and numbers must be used to indicate multiple double or triple bonds. C = C – C = C 1,3-butadiene 4 1 2 3 C 3-methyl-1,4-pentadiyne C ≡ C – C – C ≡ C 4 1 2 3 5

  13. Alkenes: C=C, CnH2n , –ene. • Alkynes: C≡C, CnH2n-2 ,–yne. • Parent chain is numbered to give the double or triple bond the lowest number. • Draw the parent chain hydrocarbon with the double or triple bonds first. • Add in alkyl groups and then hydrogen so each • carbon has 4 bonds.

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