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ALKENES ( 2 nd )

ALKENES ( 2 nd ). Dr. Marwa Eid. Alk ene s – unsaturated hydrocarbons (C n H 2n ). reactivity: the double bond is responsible for their reactivity oxidation - -bond is attacked by oxidizing agents CH 3 - CH=CH -CH 3 → CH 3 - CH(OH)-CH(OH) -CH 3 (e.g. by KMnO 4 )

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ALKENES ( 2 nd )

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  1. ALKENES (2nd) Dr. MarwaEid

  2. Alkenes – unsaturated hydrocarbons(CnH2n) reactivity: • the double bond is responsible for their reactivity • oxidation - -bond is attacked by oxidizing agents CH3-CH=CH-CH3→ CH3-CH(OH)-CH(OH)-CH3 (e.g. by KMnO4) • reduction = hydrogenation = saturation of the molecule by hydrogen CH3-CH=CH-CH3→ CH3-CH2-CH2-CH3 (by H2 + Pt)

  3. Alkenes – unsaturated hydrocarbons(CnH2n) reactivity: 3.addition reactiontwo substances join together to form a compound containing all atoms present in the original substances • the double bond is transformed to the single bond, substituents are added CH2=CH2 + Br2→ Br-CH2-CH2-Br = halogenation CH2=CH2 + HCl → CH3-CH2-Cl = halogenation CH2=CH2 + H2O →CH3-CH2-OH = hydration

  4. Alkenes – unsaturated hydrocarbons(CnH2n) ! Markovnikov´s rule ! • for unsymmetrical reagents „HX“ • „hydrogen atom of the reagent HX binds to the unsaturated carbon that has the greater number of dirrectly bonded hydrogen atoms“

  5. Addition of Alcohols • Alcohols + alkenes ethers. • For example, addition of CH3OH to 2-methylpropene, forms tert-butyl methyl ether (MTBE), a high octane fuel additive.

  6. Addition of Halogen • Halogenation is the addition of X2 (X = Cl or Br) to an alkene to form a vicinal dihalide.

  7. polymerization • “polymers“ are high molecular weight molecules made from thousands of repeating units, which are low molecular weight molecules (“monomers“) • it is a multiple addition reaction of alkenes e.g. n CH2=CH2→ (-CH2-CH2-)n • properties of polymers depend on the monomer used and MW of the product • polymer: Greek: poly, many and meros, part • monomer: Greek: mono, single and meros, part

  8. POLYMERISATION OF ALKENES ADDITION POLYMERISATION Process• during polymerisation, an alkene undergoes an addition reaction with itself • all the atoms in the original alkenes are used to form the polymer • long hydrocarbon chains are formed the equation shows the original monomer and the repeating unit in the polymer ethene poly(ethene) MONOMER POLYMER n represents a large number

  9. POLYMERISATION OF ALKENES EXAMPLES OF ADDITION POLYMERISATION ETHENE POLY(ETHENE) PROPENE POLY(PROPENE) CHLOROETHENE POLY(CHLOROETHENE) POLYVINYLCHLORIDE PVC POLY(TETRAFLUOROETHENE) PTFE “Teflon” TETRAFLUOROETHENE

  10. H H H H H H H H H H C C C C C C C H C C C H H H H H H H H H H poly(e)thene pressure high temperature catalyst n n ethene Production of polythene And lots more... 1 2 3 4 5 thousands This is called addition polymerization and is written as:

  11. THE END

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