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Alkenes

p. s. Alkenes. C n H 2n. sp 2 hybridized carbons. p. sp 2. H. H. C. C. H. H. Alkenes. Cl. Cl. Cl. H. cis -. trans -. Cl. H. Cl. Cl. no rotation at C = C. geometric isomers. Nomenclature. 1. Longest chain with C = C is parent.

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Alkenes

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  1. p s Alkenes CnH2n sp2 hybridized carbons p sp2 H H C C H H

  2. Alkenes Cl Cl Cl H cis- trans- Cl H Cl Cl no rotation at C=C geometric isomers

  3. Nomenclature 1. Longest chain with C=C is parent. 2. C numbered from end nearest to C=C. 3. Designate cis- or trans- if necessary. 4. Name substituents. 5. Replace ane with ene ending. 6. If more than one C=C, give smallest numbers and call diene or triene.

  4. Nomenclature 1 2 4 6 8 octene trans- 2- 3 5 7 octene cis- 2- hex ene adi trans- 5-methyl- 3-propyl- 1,3- 3 5 3-propyl 1 2 4 6 5-methyl

  5. Alkene - reactions  electrons Lewis Base Lewis Base e- pair donor nucleophile Lewis Acid e- pair acceptor electrophile

  6. Addition Reactions + Hrxn = bonds broken - bonds formed Hrxn = (-bond + -bond) - (2 -bonds) < 0 exothermic

  7. H3C H3C H H H H H H C C C C Cl H H Cl H3C H C C H H Addition of HX H+ + Cl- + reaction mechanism Lewis base  electrons nucleophile Lewis acid H+ electrophile

  8. H H3C C C H H Addition of HX step 1 + H-Cl H+ + Cl- H+ 2o carbocation 1o carbocation

  9. Addition of HX 2o carbocation 1o carbocation most stable intermediate Stability of carbocations 3o > 2o > 1o carbocations are e- deficient electrophiles react with nucleophile Lewis acids Lewis base

  10. Addition of HX step 2 major product minor product

  11. Markovnikov’s Rule major product minor product 2-chloropropane 1-chloropropane C with the most H gets the H

  12. Alkane Summary 1. Alkanes -sp3 hybridized 2. Relatively unreactive Substitution with halogens (hn) Combustion 3. Non-polar IMF = London Dispersion Forces size structure

  13. 4. Free rotation around C-C bonds conformations 5. Non-cyclic alkanes - structural isomers 6. Cyclic alkanes - geometric isomers cis-, trans- 7. Alkanes -optical isomers stereocenters C*

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