Short Summary

Chapter 4, Carbon and its Compounds, explains the unique bonding nature of carbon and the vast variety of organic compounds it forms. Carbon achieves stability by sharing its four valence electrons to form strong covalent bonds, a property known as tetravalency. Its unique ability to bond with other carbon atoms to form long chains, branches, or rings, known as catenation, allows it to form an immense number of compounds. Carbon also exists in different physical forms called allotropes, including diamond, graphite, and fullerenes. Compounds made entirely of carbon and hydrogen are called hydrocarbons and are classified as saturated, containing only single bonds such as alkanes, or unsaturated, containing double or triple bonds such as alkenes and alkynes. Compounds containing the same functional group belong to a homologous series, in which each consecutive member differs by a CH₂ unit and 14 u in mass. Carbon compounds commonly undergo combustion, producing carbon dioxide, water, heat, and light; oxidation reactions, such as the conversion of ethanol into ethanoic acid; addition reactions, which are used in the hydrogenation of vegetable oils; and substitution reactions. Ethanol and ethanoic acid are important carbon compounds that react together in the presence of an acid catalyst to form sweet-smelling esters. When an ester reacts with a strong base, it produces the sodium salt of a carboxylic acid and an alcohol in a process called saponification, which is widely used in soap making. Soaps cleanse by forming structures called micelles, in which the hydrophobic hydrocarbon tail traps dirt and oil while the hydrophilic ionic head interacts with water. Synthetic detergents are often more effective than soaps in hard water because they do not form insoluble precipitates, commonly known as scum, with calcium and magnesium ions.