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ORGANIC CHEMISTRY. HYDROCARBONS. H H C C H H. OR CH 2 CH 2. H H C C H CH 3. PROPENE CH 2 CH CH 3. CH 3 C CH 2 CH 3. CH 3 CH CHCH 3. CH 3 CH 2 CH CH 2. Examples of Alkenes. ETHENE, C 2 H 4.

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  2. H H C C H H OR CH2 CH2 H H C C H CH3 PROPENE CH2CH CH3 CH3C CH2 CH3 CH3CH CHCH3 CH3CH2CHCH2 Examples of Alkenes ETHENE, C2H4 TASK: Use ball & stick models or sketches to construct and name 3 different structures for C4H8 each one with one double bond. BUT-1-ENE 2METHYL PROP 1 ENE BUT-2-ENE

  3. CH2 CHCH2CH2CH3 CH3CH2CH CHCH2CH3 CH2 C(CH3)CH2CH3 CH3CHCHCH2CH3 CH2 CHCH(CH3)CH2CH3 CH3CH(CH3)CH CHCH2CH3 (CH3)3CCH C(CH3)2 More Alkenes Illustrate structures of the following alkenes: Pent-1-ene Hex-3-ene 2-methylbut-1-ene Cyclohexene Name the following alkenes Pent-2-ene 3-methylpent-1-ene 2-methylhex-3-ene 2,4,4-trimethylpent-2-ene

  4. Alkynes H-C≡C-H Ethyne Very reactive Triple bond unstable! Attracts electrophiles. H-C≡C-CH3 propyne H-C≡C-CH2-CH3 But–1-yne But–2-yne CH3-C≡C-CH3

  5. Naming Aromatics • Same rules • If benzene is the parent chain “benzene” suffix • If benzene is a branch group “phenyl”

  6. Structural Isomers • Structural isomers are compounds with the same molecular formula but different structural arrangements • They will have different physical and chemical properties • Example: • pentane • 2-methylbutane • 2,2-dimathylpropane

  7. Cis-Trans Isomers • Cis-trans isomersoccur when different groups of atoms are arranged around a double bond • Unlike a single C-C bond that can rotate, the double C=C bond is fixed Opposite side Same side cis-1,2-dichloroethene trans-1,2-dichloroethene

  8. BUT–2-ENE CH3 CH CH CH3 CH3 CH3 C C H H CH3 H C C H CH3 GEOMETRIC ISOMERS • There is no rotation about the doublebond. GEOMETRIC ISOMERISM each C atom in the doublebond has two differentatoms/groups attached. trans but-2-ene cis but-2-ene Geometric isomerism is a form of STEREOISOMERISM – Same molecular and structural formula but atoms are arranged differently in space

  9. All Hydrocarbons will Undergo Combustion:Complete:CH4 + 2O2 CO2 + 2H2OIncomplete:CH4 + O2 CO2 + CO + C + H2O

  10. Alkanes & Aromatics Undergo Substitution Reactions • One or more of the hydrogen atoms can be replaced by a halogen • You can then add other functional groups by replacing the halogen • Requires heat, UV light or a catalyst (not easily done with alkanes! But is easier with aromatics) • Alkane + halogen → hydrogen halide + alkyl halide

  11. Alkenes & Alkynes Undergo AdditionReactions:· Much greater chemical reactivity than alkanes· Easily undergo addition reactions at room temperature (calledaddition reaction b/c there is no loss of hydrogen atom(s))

  12. Addition Reactions • ReactantsProductDescriptive Name • \ / | | • C = C + HX → - C – C - Hydrohalogenation • / \ | | (X = Br, F, I, Cl…) • X

  13. Markovnikov’s Rule:When a hydrogen halide (e.g. HBr) or water (HOH) is added to an alkene the hydrogen atom will bond to the carbon atom within the multiple bond that already had more hydrogen atoms.CH3-CH2-CH=CH2 + HCl -------------------------> CH3-CH2-CH(Cl)-CH3 This rule doesn't apply for the addition of symmetrical reagents like Br2 or Cl2

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