CHEM 350 Lecture Notes - Lecture 3: Protic Solvent, Steric Effects, Cyclohexane

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26 Jan 2018
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Stereochemistry: elimination, biomolecular, anti periplanar- staggered, lower in e. no rearrangement. Rate= k[halide][base: h/x on opposite sides, minimizes steric hindrance, meso-1,2 dibromo- 1,2 diphenylethane w/base gives e alkene (bc ph"s on same side, cyclohexane rings. If rr or ss gives z-alkene (ph"s opposite side) Rate= k[halide: not stereospecific. (once carbocation- can be cis/trans but not equal, can rearrange. Nucleophile: trans-di-axial (trans position + points axial) If halogen in equatorial position, ring flip to axial. Strong base attacks a hydrogen, h-bond attacks the c-bond, c bond attacks halogen. B (+)-h forms: x- forms: deuterium isotope effect: c-h bond is weaker than c-d bond so c-h breaks & cleavage is faster. There may be 2 adjacent hydrogens and then 2 products may form zaitsev"s rule applies. Tertiary> secondary: primary- strong steric base, tert- basic. The difference between e2 and sn2 is the base. More likely to use a strong bulky base. First step= rate limiting step: leaving group leaves 2.