Alcohols & Ethers Reagents

Question 1

Answer 1

Williamson Ether Synthesis
- involves an alcohol, a base, & an alkyl halide
- makes ethers from alcohols & alkyl halides
- preferred method is less sterically hindered Halide
- to make alkoxide ion 1st, you can react with NaH a very strong base that will bubble off

Question 2

Answer 2

Ethers made from Alkenes via acid + alcohol solvent
- similar to the hydration of alkenes with
aqueous acid. Acid leads to the formation of a C+, which is then trapped by the Alcohol Solvent.
- C+ rearrangements possible

Question 3

Answer 3

Ethers made from Alkenes via oxymercuration + alcohol solvent
- similar to the hydration of alkenes with
aqueous acid.
- Key difference is NO C+, so no rearrangements possible

Question 4

Answer 4

Ethers made from Alcohols via dehydration
- Strong acid + Heat = protonation of the alcohol,
then nucleophilic attack of a 2nd molecule of
alcohol to give the ether.
- Only practical for the synthesis of SYMMETRICAL ETHERS!!!!!

Question 5

Answer 5

Epoxidation from an Alkene
- m-CPBA converts alkenes to epoxides, a cyclic ether
- ring opening reaction can be done next…..

Question 6

Opening of Epoxides
Due to ____________, epoxides are highly reactive towards nucleophiles. They will react with nucleophiles under both Acidic & Basic conditions. However the patterns are different.

Answer 6

ring strain

Question 7

Answer 7

Ring Opening under Basic Conditions
- Nuc attacks less substituted C
- Water or alcohol protonates O

Question 8

Answer 8

Ring Opening under Acidic Conditions
- Acid protonates the O
- Weak Nuc attacks more substituted C

Question 9

Oxidation of primary alcohols to aldehydes via ___________

Answer 9

Question 10

Oxidation of secondary alcohols to ketones via ____________

Answer 10

Question 11

Oxidation of primary alcohols to carboxylic acids via _________________

Answer 11

Question 12

Alternative reagents for oxidation of primary alcohols to aldehydes and secondary alcohols to ketones

Answer 12

Question 13

Reduction of Carboxylic Acid to Primary Alcohol via __________

Answer 13

LiAlH4 (LAH)

Question 14

Reduction of Carboxylic Acid to Aldehyde via __________

Answer 14

Can’t do directly
Must use LiAlH4 to get Primary Alcohol, then use PCC to convert to Aldehyde

Question 15

Reduction of Aldehyde to Primary Alcohol via __________

Answer 15

NaBH4
or LiAlH4

Question 16

Reduction of Ketone to Secondary Alcohol via __________

Answer 16

NaBH4
or LiAlH4

Question 17

Why need to convert Alcohols to good leaving groups?

Answer 17

The hydroxide group (HO–) of alcohols is a strong base and a poor leaving group.
Converting to a halogen or “sulfonate” (e.g. tosylate or mesylate) greatly facilitates Substitution Reactions

Question 18

Answer 18

Dehydration of Alcohols via POCl3 + Py
- goes E2 so no C+rearrangement
- POCl3 converts OH to good LG
- Py removes Beta Hydrogen

Question 19

Answer 19

Alcohols to Alkyl Halides via Acids
- methyl + primary = Sn2
- secondary + tertiary = Sn1
- HCl must use ZnCl2 catalyst

Question 20

Answer 20

Alcohols to Alkyl Chlorides
- converts primary & secondary alcohols into alkyl chlorides via Sn2
- secondary will see INVERSION of configuration

Question 21

Answer 21

Alcohols to Alkyl Bromides
- converts primary & secondary alcohols into alkyl bromides via Sn2
- secondary will see INVERSION of configuration

Question 22

Answer 22

Alcohols to Mesylates
- Methanesulfonyl chloride (mesyl chloride, MsCl)
- do not change the stereochemistry (RETENTION of configuration)
- a good LG that can now go Sn2 or E2

Question 23

Answer 23

Alcohols to Tosylates
- p-toluenesulfonyl chloride (Tosyl chloride, TsCl)
- do not change the stereochemistry (RETENTION of configuration)
- a good LG that can now go Sn2 or E2