Chemistry of Alcohols

Alcohols

• Alcohols are organic compounds containing a hydroxyl (-OH) group bonded to a carbon atom.
• They are classified based on the number of carbon atoms bonded to the carbon atom bearing the hydroxyl group (primary, secondary, tertiary).
• General formula: R-OH, where R is an alkyl group.
• Nomenclature: The -e ending of the corresponding alkane is replaced by -ol. For example, methane becomes methanol.
• Properties: Alcohols are generally polar due to the presence of the hydroxyl group. They can form hydrogen bonds with each other and with water, which leads to higher boiling points compared to alkanes of similar molecular weight.
• Physical properties: Lower molecular weight alcohols are miscible with water, but solubility decreases with increasing molecular weight.
• Chemical properties: Alcohols can undergo various reactions, including oxidation, esterification, and dehydration. Oxidation reactions can convert primary alcohols to aldehydes and then to carboxylic acids; secondary alcohols are oxidized to ketones; tertiary alcohols are resistant to oxidation.
• Uses: Alcohols exhibit a wide variety of uses including solvents, fuel, and in the production of other chemicals. Ethanol is commonly used as a beverage and in various industrial applications.

Phenols

• Phenols are aromatic compounds containing a hydroxyl (-OH) group directly bonded to an aromatic ring.
• Chemical properties: Phenols are more acidic than alcohols due to the resonance stabilization of the phenoxide ion. This acidity is crucial for many of their reactions. Unlike alcohols, they readily react with sodium hydroxide.
• Nomenclature: The -e ending of the corresponding benzene derivative is replaced by -ol. For example, benzene becomes phenol.
• Physical properties: Phenols are generally less soluble in water than alcohols. They tend to be more reactive than alcohols due to resonance effects.
• Uses: Phenols are used in the production of various materials, including plastics, resins, and other industrial chemicals. Phenols also have antiseptic applications.
• Note: Their acidity and reactivity are significantly different from that of alcohols, due primarily to the interaction between the aromatic ring and the -OH.

Esters

• Esters are organic compounds derived from the reaction between an acid (typically a carboxylic acid) and an alcohol.
• General formula: RCOOR', where R and R' are alkyl or aryl groups.
• Formation: This reaction, called esterification, involves the loss of a water molecule between the carboxylic acid and alcohol.
• Nomenclature: The name is derived from the alcohol and acid parts of the molecule. The -oic acid part of the acid name changes to -ate. For example, methanol and ethanoic acid react to form methyl ethanoate.
• Physical properties: Esters typically have lower boiling points than the corresponding carboxylic acids. They are generally less polar than alcohols or carboxylic acids. Many are volatile liquids with pleasant odors – a feature harnessed in fragrances and food flavorings.
• Chemical properties: Esters can undergo various reactions with bases, such as hydrolysis, which regenerates the acid and alcohol.
• Uses: Esters are widely used in flavors, fragrances, plasticizers, and in the synthesis of other compounds. Methyl salicylate (aspirin), for example, is an ester.