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

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

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.

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

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

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

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

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

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

Addition of HX step 2 major product minor product

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

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

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*