7/28/2019 ZLM-chapter 10-alcohol.pdf

1/4

7/28/2019 ZLM-chapter 10-alcohol.pdf

2/4

LMZ/CHEM109A/ Winter 2010

II. Elimination and rearrangement reactions of alcohols

1. Acid catalyzed dehydration of alcohol to alkene (Sec. 10.4)

(3>2>1)

mechanism?

-carbocation rearrangement may occur

- SN2 reaction competes with E2 dehydration

2. Dehydration by POCl3

III. Oxidation of alcohols, aldehydes, and thiols

A. Oxidation of alcohols and aldehydes (Sec. 10.5)

R C

OH

H

H

R H

O[O], oxidation

1 alcohol

R OH

O

aldehyde carboxylic acid

[O]

a. Oxidation of 1 alcohols to aldehydes or carboxylic acids

N HCrO3Cl

pyridiniumchlorochromate (PCC)

e.g. Na2Cr2O7,H2O,

ethanolOr J one's reagent

(CrO3, H3O+, acetone)

OR KMnO4, H2O

e.g. Na2Cr2O7,H2O, ethanol, OR CrO3, H3O+, acetone, (OR KMnO4, H2O)

[O], oxidation

(CrO3, pyridine, HCl)

R C

OH

R'H R R'

O[O], oxidation

2 alcohol ketone

b. Oxidation of 2 alcohols to ketones

e.g. PCC, CH2Cl2OR Na2Cr2O7,H2O, ethanol

OR CrO3, H3O+, acetone

[O]

no furtheroxidation

R C

OH

R'

R"

[O], oxidation

NO REACTION

c. 3 alcohols cannot be oxidized

3 alcohol

mechanism:

IV. Amines as organic bases (sec. 10.6)

- amino (NH2-or NR2

-) is a very poor leaving group;

- amines does not undergo elimination or substitution reactions on the C-N bond.

- as base

7/28/2019 ZLM-chapter 10-alcohol.pdf

3/4

LMZ/CHEM109A/ Winter 2010

V. Nucleophilic substitution reactions of ethers (ROR)

A. RO-is poor leaving groups similar to OH

-: need acid activation

B. SN1 or SN2 mechanism (PCl

3 or TsCl not working)

VI. Epoxide (one kind of ether) ring opening (sec. 10.8)

A. Due to ring strain, much more reactive than normal ethers

B. under acidic conditions-- opened by halide, even H2O and ROH

- reaction proceeds with neither pure SN2or SN1.

- regioselectivity:

D.basic conditions:

- regioselectivity controlled by sterics

- stereochemistry: SN2

VII. Crown ethers

- help dissolve metal cations

- Na+ --- [15]-crown-5

- K+

-----[18]-crown-6- Li+ ----[12]-crown-4

7/28/2019 ZLM-chapter 10-alcohol.pdf

4/4

LMZ/CHEM109A/ Winter 2010

IX. Thiols, sulfide (sec. 10.11)

A. naming thiols- as the principle functional group, alkane + thiol (similar to alcohol case)

- naming priority: OH>SH>NH2, when treated as substituent, use 'mercapto'

B. naming sulfide: (similar to ether)

C. Strong nucleophiles due to high polarizability (softness)

X. Organometallic compounds (sec. 10.12)A. compare:

B. Organolithium compounds: prepared in alkanes- strongly basic (pKa >40), can be nucleophile as well

- C-Li bond: polarized covalent bond (not ionic bond)

C. Organomagnesium compounds -- Grignard reagents (in ethereal solvent)

- strongly basic, but less reactive than corresponding lithium compounds.

- C-Mg bond: polarized covalent bond, not ionic bond.

D. Reactions: