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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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p s Alkenes CnH2n sp2 hybridized carbons p sp2 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. 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 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
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 = (-bond + -bond) - (2 -bonds) < 0 exothermic
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
H H3C C C H H Addition of HX step 1 + H-Cl H+ + Cl- H+ 2o carbocation 1o carbocation
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
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*