Lecture_26

Lecture_26 - Lecture 26 Chapter 9: Elimina5ons ...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Lecture 26 Chapter 9: Elimina5ons Elimina5ons are Stereoselec5ve  Two ways to elimina.on Elimina5ons are Stereoselec5ve   So more E than Z in 2- bromopentane elimina.on Elimina5ons are Stereoselec5ve   E2 elimina.on of chiral centers Elimina5on from Cycloalkyl Halides   Same rules, but now the ring is limi.ng possibili.es –  E2 elimina.ons –  Equatorial halogen can’t go E2 Elimina5on from Cycloalkyl Halides   Elimina.on takes place faster when H and X are an. in the most stable conformer. Elimina5on from Cycloalkyl Halides   Conformer of menthyl chloride eliminates differently: Elimina5on from Cycloalkyl Halides   Only protons axial can be removed Elimina5on from Cycloalkyl Halides   E1 Reac.ons of Subs.tuted Cyclohexanes –  Hydrogen and halide don’t have to be axial –  Have to check for C+ before using Zaitsev’s rule Elimina5on from Cycloalkyl Halides   E1 Reac.ons of Subs.tuted Cyclohexanes Summary 9.6 Under E2 reac5on condi5ons, which alkyl halide will give predominantly the Zaitsev product? Subs5tu5on vs. Elimina5on   Secondary alkyl halide under SN2/E2 condi.ons –  Stronger/bulkier the base, more E2 •  Ethoxide is a stronger base than acetate, more elimina.on Subs5tu5on vs. Elimina5on   Secondary alkyl halide under SN2/E2 condi.ons –  Lower temp favors SN2, higher favors E2 Subs5tu5on vs. Elimina5on   Ter.ary alkyl halide under SN2/E2 condi.ons –  Hard for subs.tu.on, only E2 takes place Ques5on  Would there be more elimina.on or subs.tu.on if CH3S- was used in place of CH3O- with propyl bromide? Subs5tu5on vs. Elimina5on   Primary Alkyl Halides can’t do SN1/E1 –  Primary carboca.on too unstable   Secondary favor: –  Poor nucleophile/base (water or alcohol) –  Your gonna get both SN1/E1   Ter.ary gives mainly SN1 Subs5tu5on and Elimina5on in Synthesis  Making ethers –  Williamson Ether Synthesis –  Alkoxides are prepared by adding sodium metal to an alcohol Subs5tu5on and Elimina5on in Synthesis  Make butyl propyl ether:  Make t- butyl propyl ether: ...
View Full Document

Ask a homework question - tutors are online