Chapter 16: Ethers, Epoxides and Sulfides

Ethers

Nomenclature:
Functional group suffix =  ether (review)
Functional group prefix = alkoxy-
Ethers are said to be symmetrical if the two alkyl groups are the same, e.g. diethyl ether.
 

Questions :
What do you think the acronym MTBE stands for ? 
Is this an alternative correct IUPAC name the fuel additive ? 

Physical Properties:

• The polar nature of the C-O bond (due to the electronegativity difference of  the atoms ) results in intermolecular dipole-dipole interactions.
• An ether cannot form hydrogen bonds with other ether molecules since there is no H to be donated (no -OH group)
• Ethers can be involved in H-bonding with systems able to donate H (e.g. water).
• The implications of these effects are:
• lower melting and boiling points compared to analogous alcohols
• solubility in aqueous media similar to analogous alcohols.

• The ether functional group consists of an O atom bonded to two C atoms via s bonds.
• Both the C-O bonds are polar due to the high electronegativity of the O atom.
• The O atom in a ether chain behaves much like a -CH₂- in an alkane, use the CHIME images to compare

Questions :
What type of conformation is diethyl ether shown in the CHIME image above ?
What type of conformation is tetrahydropyran shown in the CHIME image above ?

Reactivity:

The image shows the electrostatic potential for dimethyl ether.  The more red an area is, the higher the electron density and the more blue an area is, the lower the electron density. The ethereal O atom is a region of high electron density (red) due to the lone pairs. Ether oxygen atoms are Lewis bases. Like an alcohol -OH group, the -OR group is a poor leaving group and needs to be converted to a better leaving group before substitution can occur. The most important reaction of ethers is their cleavage by strong acids such as HI or HBr.