Hydrogen, oxygen, nitrogen, and a number of other elements also bond strongly to carbon, and a tremendous variety of compounds can result. In the early days of chemistry such compounds were obtained from plants or animals rather than being synthesized by chemists, and so they came to be known as organic compounds. This distinguished them from the inorganic compounds available from nonliving portions of the earth’s surface. Today literally millions of carbon compounds can be synthesized in laboratories, and so this historical distinction is no longer valid. Nevertheless, the study of carbon compounds is still referred to as organic chemistry. 8.1: Prelude to Organic Compounds Hydrogen, oxygen, nitrogen, and a number of other elements also bond strongly to carbon, and a tremendous variety of compounds can result. In the early days of chemistry such compounds were obtained from plants or animals rather than being synthesized by chemists, and so they came to be known as organic compounds. This distinguished them from the inorganic compounds available from nonliving portions of the earth’s surface. Earth's Oldest Fossils Mars Meteor and Extraterrestrial Life 8.2: Covalent Compounds and Intermolecular Forces The ionic compounds are almost all solids with melting temperatures above 600°C. By contrast, most substances which contain simple molecules are either gases or liquids at room temperature. They can only be persuaded to solidify at rather low temperatures. The reason for this contrasting behavior is easily explained on the microscopic level. 8.3: Dipole Forces Polar molecules attract each other when the charges which are closest together are opposite in sign. Forces between polar molecules which arise in this way are called dipole forces. 8.4: London Forces An explanation of these attractive forces was first given in 1930 by the Austrian physicist Fritz London (1900 to 1954). According to his theory, when two molecules approach each other very closely, the motion of the electrons in one of the molecules interferes with the motion of the electrons in the other, and the net result is an attractive force. <pic>Chapter 8 page 3.jpg Atomic Radii Atomic sizes on periodic table.jpg Ionization Energies <pic> IonizationEnergyAtomicWeight.PNG Ionization Energies and Electron Affinities Electron Affinities <pic> Ionization Energies and Electron Affinities.jpg Polarizability on London Forces.jpg 8.5: Organic Compounds: Hydrocarbons The hydrocarbons contain only hydrogen and carbon. They provide the simplest examples of how catenation, combined with carbon’s valence of 4, gives rise to a tremendous variety of molecular structures, even with only two elements involved Crude Oil Distillation.jpg 8.6: Alkanes Most of the hydrocarbons in petroleum belong to a family of compounds called the alkanes, in which all carbon atoms are linked by single bonds. Boiling Points of Some Organic Compounds Whose Molecules Contain 32 or 34 Electrons Rockets Titan 8.7: Cycloalkanes Cycloalkanes are characterized by a ring of carbon atoms. 8.8: Properties of Alkanes <pic> boiling points.jpg Table of Electronegativities Table of Straight Chain Alkanes 8.9: Aromatic Hydrocarbons Aromatic hydrocarbons are one of the three classes of compounds found in petroleum. They are less abundant than the alkanes and cycloalkanes, amounting to only a few percent of the total, but they are quite important commercially. 8.10: Unsaturated Hydrocarbons Chapter 7 page 19-2.jpg 8.11: Hydrogen Bonding: Water Atomic Radii and Ionic Radii H-Bonding Between 2 HF Molecules.jpg Nonmetal hydride bp.jpg 8.12: Ice and Water The most important example of hydrogen bonding is that which occurs in \(H_2O\). <pic> Ice; a hexagonal crystal.jpg Boiling Points of Hydrides 8.13: Organic Compounds-Some Additional Classes 8.14: Alcohols 8.15: Ethers 8.16: Aldehydes and Ketones Ketosis The Cinnamon Trade 8.17: Carboxylic Acids Entomology 8.18: Esters 8.19: Organic Nitrogen Compounds 8.20: Macromolecular Substances 8.21: Diamond and Graphite 8.22: Silicon Dioxide 8.23: Synthetic Macromolecules: Some Applied Organic Chemistry 8.24: Addition Polymers Addition polymers are usually made from a monomer containing a double bond. 8.25: Condensation Polymers Formation of a condensation polymer produces \(H_2O\), \(HCl\), or some other simple molecule, which escapes as a gas. A familiar example of a condensation polymer is nylon, which is obtained from the reaction of two monomers. 8.26: Cross-Linking The formation of covalent bonds which hold portions of several polymer chains together is called cross-linking. Extensive cross-linking results in a random three-dimensional network of interconnected chains. Contributors Ed Vitz (Kutztown University), John W. Moore (UW-Madison), Justin Shorb (Hope College), Xavier Prat-Resina (University of Minnesota Rochester), Tim Wendorff, and Adam Hahn.