Ethers + Epoxides Reactions and Preparation

Question 1

What is the primary way to prepare ethers (R-O-R)?

Answer 1

1. NaH
2. RX, R can be a methyl or something ** REAGENT FOR 2 MUST BE A METHYL OR A FIRST DEGREE ALKYL HALIDE

Question 2

What is the alternative way to prepare ethers?

Answer 2

1. Hg(OAc)2, ROH
2. NaBH4

Question 3

What is the reaction that ethers undergo?

Answer 3

Acidic Cleavage, forms alkyl halides. reagent for the reaction is HBr or HI.

Question 4

What are the exceptions for acidic cleavage?

Answer 4

3rd degree carbons undergo cleavage under Sn1 mechanism. If the R group is aryl or vinyl, substitution doesn’t occur and alcohol is made.

Question 5

How to prepare epoxides?

Answer 5

Epoxides are formed when an alkene is treated with a peroxy acid. Two common ones are mCPBA and Peroxyacetic Acid. Stereospecific and keeps original stereochemistry

Question 6

How to prepare epoxides from halohydrins?

Answer 6

1. Br2 + H2O
2. OH- which causes deprotonation of alcohol group and causes formation of epoxide.

Question 7

What are the ring-opening reactions of epoxides?

Answer 7

These are reactions that add a nucleophile to an epoxide. Useful in multi-step synthesis.

Question 8

What is the stereoselective and regioselective aspect of ring opening reactions?

Answer 8

The nucleophile gets added to the least hindered carbon of the epoxide group = regioselectivity.
Stereoselectivity = Inverts configuration

Question 9

How do acidic reactions change the ring-opening reactions?

Answer 9

Acidic reactions allows weak nucleophiles (Water, Alcohol, HBr, and HCl) to open epoxides. Nucleophile will still attack at the least hindered carbon unless a 3rd degree carbon is present.

Question 10

Why are ring-opening reactions useful?

Answer 10

When using an epoxide, allows for the addition of a functional group on the second carbon.
When using a carbonyl, allows for the addition of a functional group on the first carbon.