# Organic Chemistry/Ethers

# Ethers

Ethers can be derived from alcohols. The functional group of ethers is
**R-O-R** (instead of R-O-H in an alcohol). Ethers can be viewed as a
water molecule in which both H atoms are replaced with alkyl groups.
Ethers may exist in straight chain carbons (acyclic) or as part of a
carbon ring (cyclic).

!Example ethers. MTBE is acyclic. THF is
cyclic.

# Preparation of ethers

### Synthesis of acyclic ethers

Most acyclic ethers can be prepared using **Williamson\'s synthesis**.
This involves reacting an alkoxide with a haloalkane. As stated
previously, alkoxides are created by reacting an alcohol with metallic
sodium or potassium, or a metal hydride, such as sodium hydride (NaH).
To minimize steric hindrance and achieve a good yield, the haloalkane
must be a primary haloalkane. This is because the mechanism is S~N~2,
where the oxygen atom does a backside attack on the carbon atom with the
halogen atom, causing the halogen atom to leave with its electrons.

### Synthesis of cyclic ethers

You can also use the Williamson synthesis to produce cyclic ethers. You
need a molecule that has a hydroxyl group on one carbon and a halogen
atom attached to another carbon. This molecule will then undergo an
S~N~2 reaction with itself, creating a cyclic ether and a halogen anion.

# Properties of ethers

## Acyclic ethers

### Naming acyclic ethers

Name the two sides of the ether as substituents, then add the word
\"ether\" at the end. For example, CH~3~-O-CH~3~ is dimethyl ether.
CH~3~-O-C(CH~3~)~3~ can be called methyl *tert*-butyl ether (MTBE) or
*tert*-butyl methyl ether (TBME).

### Cleavage of acyclic ethers

Acyclic ethers can be cleaved by a strong acid, typically HI or HBr, but
not HCl. The acid breaks the ether apart into an alcohol and an alkyl
halide (a haloalkane.) Cleavage of ethers by an acid was first seen by
Alexander Butlerov in 1861, when he discovered that hydroiodic acid
causes 2-ethoxypropanoic acid to break apart into iodoethane (ethyl
iodide) and lactic acid (2-hydroxypropanoic acid.) The mechanism used in
acidic cleavage of ethers depends on whether they have primary,
secondary, or tertiary groups attached to oxygen. If one of the carbons
attached to the central oxygen atom is tertiary, benzylic (contains
benzene ring), or allylic (contains carbon-carbon double bond), then the
cleavage will occur via an S~N~1 or an E1 mechanism. The E1 mechanism
leads to an alcohol and an alkene instead of an alkyl halide. These
reactions often take place around 0 degrees C. On the other hand, if
both groups attached to the central oxygen atom are primary or
secondary, the reaction takes place via an S~N~2 mechanism. These
reactions are often conducted at 100 degrees C.

## Cyclic ethers

Two common cyclic ethers are epoxide, which has
two carbons each bonded to the oxygen atom; and
tetrahydrofuran, known by its
abbreviation THF, which has four carbons and an oxygen atom.

### Naming cyclic ethers

### Synthesis of cyclic ethers

### Cleavage of cyclic ethers

