Alkenes sp 2 hybridized carbons sp 2 p CC H H H H C n H 2n s p

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

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 hex ene 1,3-5-methyl-3-propyl-trans octene trans- 2- octene cis- 7 3-propyl 5-methyl adi

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

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

Addition of HX + reaction mechanism Lewis base Lewis acid  electrons H+H+ nucleophile electrophile H + + Cl - C H3CH3C H H H H3CH3C H H H HCl C H3CH3C H H H ClH

Addition of HX step 1 carbocation 2o2o 1o1o CC H HH H3CH3C + H-ClH + + Cl - H+H+

Addition of HX carbocation 2o2o 1o1o Stability of carbocations3 o >2 o >1o1o most stable intermediate carbocations are e - deficient electrophiles Lewis acids react with Lewis base nucleophile

Addition of HX step 2 major product minor product

Markovnikov’s Rule major productminor product 2-chloropropane1-chloropropane C with the most H gets the H

Alkane Summary 1. Alkanes - sp 3 hybridized 2. Relatively unreactive Substitution with halogens (h ) 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* C*