Question

What is the main structural difference between an alcohol or phenol and an ether and how does this affect reactivity of an ether?

Answer 1

Alcohols, phenols, and ethers may be considered organic derivatives of water (H₂O). A water molecule consists of an oxygen atom bonded to two hydrogen atoms. In an alcohol, one of water's two hydrogen atoms is replaced by an alkyl group, which is a hydrocarbon chain, typically represented by R in organic structures. In ethanol, for example, the alkyl group is the ethyl group, -CH₂CH₃.

A phenol is simply an aromatic alcohol, with an aryl group, or aromatic ring (Ar), bonded to the oxygen atom. (See above Hydrocarbons: Aromatic hydrocarbonsfor a discussion of the special properties of aromatic rings.) An ether has two hydrocarbon groups, either alkyl groups or aryl groups, bonded to the oxygen atom.

Alcohols may also be considered organic compounds with the hydroxyl group (-OH) as their functional group. Alcohols are among the most polar organic compounds, because the hydroxyl group is strongly polar and can participate in hydrogen bonding with other alcohol molecules or with water molecules. Because they form hydrogen bonds with water, alcohols are more soluble in water than are the corresponding unsubstituted alkanes. For example, the alcohols shown below are miscible with water.

lcohols are also valuable as intermediates in the synthesis of other compounds. Many methods are available for the synthesis of alcohols, and the hydroxyl group of an alcohol is easily converted to most other functional groups.

Phenols are aromatic alcohols; that is, they have an aryl group instead of an alkyl group. Most of the properties of phenols are similar to those of aliphatic(nonaromatic) alcohols: they are strongly polar and relatively soluble in water, and they undergo most of the same reactions as alcohols. Phenols are more acidic than alcohols, however, and some of their reactions (especially oxidation) are different from those of aliphatic alcohols.

Ethers have two alkyl (or aryl) groups bonded to an oxygen atom. Although the structure of an ether is similar to that of an alcohol or phenol, an ether has no hydroxyl group and cannot engage in hydrogen bonding with other ether molecules. Diethyl ether (CH₃CH₂-O-CH₂CH₃, also called ethyl ether or simply ether) is the most common variety. It is widely used as a solvent and as a volatile, combustible starting fluid for engines.