Alcohol Physical Properties and Uses

• Alcohols are a class of organic compounds with a hydroxyl (-OH) functional group.

Physical Properties of Alcohols

• Alcohols form hydrogen bonds due to the electronegativity of oxygen in the hydroxyl group.
• Greater electronegativity of oxygen compared to carbon and hydrogen
• C-O and O-H bonds are polar.
• Boiling points increase with hydrogen bonds and the number of carbon atoms.
• Boiling points increase if containing more than one hydroxyl group.
• Boiling points decrease with branching between isomers.
• Density of alcohols increases with the molecular weight of the alcohol.
• Alcohols are soluble in water due to hydrogen bonds.

Uses of Alcohols

• Methanol is used as a solvent and as a raw material for the production of formaldehyde.
• Ethanol is a main component of alcoholic beverages.
• Ethanol is also used as antifreeze, with a freezing point of -114°.
• Ethanol is found in perfumes, lubricants and sweeteners.
• Ethanol is used as fuel when mixed with gasoline, producing gasohol.
• The world's top ethanol fuel producers in 2011 were the United States and Brazil, accounting for 87.1% of world production.
• Glycerol is used in cosmetic creams, liquid medicines and suppositories due to its moisturizing properties.
• Glycol is used as antifreeze in car radiators due to its low freezing temperature.
• Glycol is also used to make coolant, a 50:50 mixture of antifreeze and water.
• Isopropyl alcohol is used as rubbing alcohol because it is an antiseptic.
• Cetyl Alcohol includes 16 carbons used as a solid substance in cosmetics and creams to lubricate and soften the skin.

Sources and Obtaining Alcohols

• Alcohols can be obtained through alcoholic fermentation.
• Industrial production of ethanol involves fermentation of carbohydrates from sugarcane, barley, or corn with yeast.
• Whiskey is made from fermented grains like rye, wheat, corn, or barley.
• Beer results from the fermentation of malted barley.
• In the laboratory, alcohols can be synthesized through the addition of water to an alkene, using an acid medium as a catalyst.

Chemical Properties of Alcohols

• Alcohols undergo dehydration.
• Alcohols can react as acids and bases (amphoteric).
• Alcohols undergo oxidation of different types.
• Alcohols undergo combustion.

Chemical Properties of Alcohols: Acidity and Basicity

• Alcohols are amphoteric substances that can react as either an acid or a base.
• Alcohols react as acids against metallic sodium, forming an alkoxide.
• An alkoxide is an organic functional group formed when a hydrogen atom is removed from the -OH group and is substituted by a metal; alkoxides are strong bases.
• The general formula of alkoxides is R-O(-) Na(+).
• Alcohols react as bases against a hydracid (HX) forming an alkyl halide.
• Alkyl halides are organic functions that have hydrocarbons with halogen atoms.
• The gernal formula for alkyl halides is RX, where X represents the halogen.

Chemical Properties of Alcohols: Oxidation

• Common oxidizing agents of alcohols are potassium permanganate (KMnO4), chromic acid (H2CrO4), and potassium dichromate (K2Cr2O7).
• Either one can be represented with the symbol [O].
• Primary alcohols are first oxidized to aldehydes; if oxidation continues, it forms a carboxylic acid.
• Secondary alcohols are oxidized into ketones.
• Tertiary alcohols are resistant to oxidation.

Chemical Properties of Alcohols: Combustion

• Combustion of methanol is an exothermic reaction.
• 2CH3OH(g) + 3O2(g) → 2CO2(g) + 4H2O(l)

Alcohols are organic compounds containing a hydroxyl group. Their boiling points increase with hydrogen bonds and the number of carbon atoms. They are widely used as solvents, in beverages, antifreeze, perfumes, lubricants and as fuel.