Alkenes: Reactions with carbenes (McM 7.6) cont. Alkenes: Addition of radicals etc - Polymerisation (McM 7.10, 14.7) Alkenes:Formation by elimination reactions (McM 11.12, 11.13) Substitution reactions:Cleavage of ethers (McM 18.5) Organometallic coupling react. (McM 10.9, lab ex 10)

Polymerization of dienes (McM 14.7) Radical polymerization Cationic polymerization Natural and synthetic rubber Acid cat polymerization of 1,3-butadiene 1,4-addition

resin from the Isonandra Gutta tree (South east Asia) Less elastic than nat. rubber Isolation under-water cables Little use today Hevea brasiliensis, tropical Americas. Cautchuc

Elimination reactions - Repetition One step 2. order Stereospecific Two steps 1. order 1. step rate limiting 1.step = 1. step in S N 1 Not stereospecific Elimination in competition with substitution

E2 and stereochemistry Large subst in e pos. favored

Deuterium Isotope Effect (McM 11.14) (Kinetic Isotope Effect) Important in elucidation of reaction mechanisms Cleavage of C-H and C-D requires different amount of energy Hookes Law, Stretching frequencies, IR Relationship between Streching frequency (  and zero-point energy (E 0 ) E 0 = 1/2 h E 0 C-H 18 kJ/mol E 0 C-D 13 kJ/mol Higher activation energy for cleavage of C-D Cleavage of C-H will be faster TS #

Substitution reactions - Repetition One step 2. order Stereospecific - Inversion Sterical hindrance Two steps 1. order 1. step rate limiting 1.step = 1. step in E1 Not stereospecific - Racimisation Stabilisation of carbocation X: Leaving group, Godd leaving group - weak base

C-C Bond Formation - Organometallic Coupling Reactions (McM 10.9, Lab ex 10)

Grignard reagents and Organolithium reagents Reacts with carbonyls Strong bases RMgX or RLi does not react well with alkyl halides in substitutions

Organocuprates (McM 10.9) Gilman reagent Dialkylcuprate Participate in substitution with alkylhalides (Cl, Br, I) (R: alkyl, alkenyl, alkynyl, aryl) Also reaction with alkenyl halides and arylhalides (sp 2 ) Not S N 1 or S N 2

Palladium catalyzed coupling reactions (Lab ex. 10) Met: -ZnX, -B(OH) 2, -SnR 3 (-MgX) Alkenyl or aryl halides Pd complex from aklyl halides unstable Alkynyl, alkenyl, aryl, alkyl reacts (depending on the metal used)