1. Chapter 9 Alcohol Reactions
Reactions of Alcohols with Acids and Bases
Preparations of Alkoxides
To deprotonate an alcohol, Base more basic than RO-
Alkali Metal Reductions give Alkoxides
2 H2O Na (Li, K, Cs) Na+OH H2 (Violent!)
2 ROH Na Na+OR H2
Reactivity: MeOH > primary > secondary > tertiary

2. 3) Uses of Alkoxides
Strong base for E2 reactions
Ether synthesis by SN2 reactions (stay tuned!)
Protonation of Alcohols form a better Leaving Group
X ROH RX OH- (OH- is a poor leaving group)
Strong acid converts OH- leaving group to H2O (good leaving group)
Synthesis of Haloalkanes from Alcohols
Only I- and Br- are nucleophilic enough to work
Works best for primary alcohols

3. 4) Reaction of Secondary and Tertiary ROH with H+
a) Secondary and Tertiary alcohols easily lose water to from carbocations
If the acid contains a good nucleophile, you get SN1 substitution
If there is no nucleophile or have high Temperature, you get E1
Dehydration = loss of an H2O molecule
Use non-nucleophilic acid = H2SO4, H3PO4
As usual, Tertiary ROH only does SN1, E1 while Secondary ROH can do SN2, SN1, or E1 in a strong acid
Catalytic

4. Carbocation Rearrangement
Hydride Shift
Sometimes we get mixtures of products from 2o and 3o ROH reactions
How does the rearrangement occur?
Carbocation intermediate rearranges
Hydrogen and both electrons move = hydride shift
Mechanism
H:- and + trade places
Very fast (faster than SN1/E1)
if new C+ more stable

5. Orbital Picture of the Hydride Shift Mechanism
Primary ROH/RX won’t form carbocations, so don’t do Hydride Shift
Secondary and Tertiary ROH give mixture of products with nucleophile

6. Mixture of E1 Products are also observed at high Temp., no nucleophile
B. Alkyl Shifts
If the carbocation doesn’t have a H- positioned to shift, an alkyl group can move = Alkyl Shift

7. Ester Formation from Alcohols
Hydride and Alkyl Shifts occur at about the same rate
Very fast if rearranged carbocation is more stable
Formation of tertiary carbocation is faster than secondary
Concerted Hydride and Alkyl Shifts in Primary Alcohols
Primary alcohol will not form a carbocation, but sometimes rearranged products are observed anyway
Only observed with much heat and much time
Concerted mechanism explains how
Ester Formation from Alcohols
Esters are derivatives of organic and inorganic acids

8. Synthesis of Organic Esters
Subject of chapters 19 and 20
Synthesis of Haloalkanes from Alcohols involves Inorganic Esters
R—OH + HBr R multiple products
Use Inorganic Reagent to make the water leaving group
1o or 2o ROH + PBr o or 2o RBr H3PO3
Mechanism
Reaction also works to make iodoalkanes with PI3
Chlorination of an alcohol requires thionyl chloride = SOCl2

9. Mechanism
Amine works as a base to remove H+ from reaction
Alkyl Sulfonates in Substitution Reactions
Preparation of Alkyl Sulfonates (good leaving groups)
Substitution reactions take advantage of the good sulfonate leaving group