Nomenclature of alcohols. Alcohols are aliphatic compounds that contain the hydroxyl functional group (-OH). Several alcohols are well known by common names. In the IUPAC system, the suffix -ol or the prefix hydroxy- is used to designate alcohols. Aromatic compounds with an -OH group attached to the ring are called phenols.
Classification of Alcohols. Alcohols are classified on the basis of the number of carbon atoms which are bonded directly to the carbon which is attached to the OH group. In. primary (1oalcohols the OH- bonded carbon is bonded to one other carbon. In secondary alcohols (2othe OH-bonded carbon is bonded to two other carbons. In tertiary (3oalcohols the OH-bonded carbon Is bonded to three other carbons.
Physical properties of Alcohols. Hydrogen bonding can occur between alcohol molecules, and between alcohol molecules and water. As a result, alcohols have higher boiling points than hydrocarbons of similar molecular weight, and low molecular weight alcohols are soluble in water.
Reactions of Alcohols.
Common Alcohols.
| methanol | solvent and fuel (wood alcohol) | b.p. 66 oC |
| ethanol | alcoholic beverages | b.p. 78 oC |
| isopropyl alcohol | rubbing alcohol | b.p. 82 oC |
| ethylene glycol | antifreeze | b.p. 198 oC |
| glycerol | a moistening agent | b.p. 290 oC |
Denatured alcohol is ethanol intended for industrial or research uses is made unfit for internal consumption by addition of small quanitites of a poison.
Characteristics and Uses of phenols. Phenols are named as derivatives of the parent compound phenol. Phenols are weak acids which are widely used for their antiseptic and disinfectant properties. Some phenols are used as antioxidants in foods and a variety of other materials.
Ethers. Ethers contain an oxygen attached to two carbons as the characteristic functional group. In the lUPAC system, ethers are named as alkoxy derivatives of alkanes. The -O-R group is the alkoxy group which may have names such as methoxy (-O-CH3) or ethoxy (-O-CH2CH3). The simplest and most important compound of this class is ethyIene oxide.
Properties of Ethers. Like the alkanes, ethers are very unreactive substances. Pure ethers cannot form hydrogen bonds. As a result, their boiling points are comparable to those of hydrocarbons and lower than those of alcohols of similar molecular weight. Ethers are much less polar than alcohols but are still slightly soluble in water due to the limited formation of hydrogen bonds.
| Compound | Mol. Wt. | B.P., oC | Solubility in water |
| butane | 58 | 0 | insoluble |
| ethyl methyl ether | 60 | 11 | soluble |
| 1-propanol | 60 | 97 | soluble |
| ethylene glycol | 62 | 198 | soluble |
Thiols. Thiols contain an -SH group which often imparts a very strong, often pungent odor to the compound. Two reactions of thiols that are important in protein chemistry are their oxidation to produce a disulfide and their reaction with heavy metals, such as mercury. Disulfides may be converted back to thiols by a reducing agent.