Reactions Of Alcohols, Ethers And Epoxides

Question 1

H2SO4 or TsOH

Answer 1

Dehydration reaction
Protonation to make OH good leaving group
2’ or 3’ alcohol E1 (product is Alkene)2 step, carbon cation (planar)
1’ alcohol E2(product is alkene) concerted

Question 2

POCl3

Answer 2

Assume dehydration

Question 3

Carbocation rearrangement

Answer 3

If already 3’ then no shift will occur

2’ shifts to 3’ to become more stable

Question 4

Conversion of Alcohols to Alkyl Halides via HX mechanism

Answer 4

Protonation(forming water connected to molecule)
R-OH is protonated then X replaces OH
SN2 for 1’ alcohols
SN1 for 2’ and 3’ alcohols
creates product of inversion (umbrella flipping)+H2O for 1’
For 3’ creates carbocation causes inversion at stereochem 50% In front 50% in back

Question 5

Conversion of Alcohols to Alkyl Halides via PBr3 and SOCl2

Answer 5

Hint of SN2 reaction (only occurs with 1’ and 2’ or methyl) (invert stereochem)
100% inversion
Cl or Br replaces OH then flip stereochem 100%
Only place where stereochem is flipped is where OH was (Cis becomes trans just with Br)

Question 6

Reactions of ethers with strong acids

Answer 6

Performed in excess
R-I + R’-I +H2O
Both halves of ether each connect to halogen to form two products plus water

Question 7

What if reactant alcohol would undergo side reaction with HX or H2SO4

Answer 7

TsCl
Convert to tosylate
Ts replaces H so leaving group is now OTS
100% retention of stereochem
100% inversion of stereochem at reactive site in presence of strong nucleophile(SN2)
Can also undergo E2 (kicks OTS) then forms alkene

Question 8

Reactions of epoxides

Answer 8

Ring opens in presence of strong nucleophile
Attacks C, doesn’t kick out leaving group like normal, opens triangle
Protonation and then OH and nucleophile opposite from one another to balance
Strong nucleophile attacks less hindered side then protonates

Question 9

Opening epoxide ring under acidic conditions (H-Cl)

Answer 9

Nucleophile attacks more substituted carbon. protonation and unfolding of triangle. Still end up opposite (furthest away from OH)

Question 10

Sulfur containing functional groups R-S-R and ethers R-O-R

Answer 10

Williamson ether synthesis (deprotonation) takes H from molecule then add CH3 to form new bond to create ether
Same thing can occur with S, just add other half of ether