Chapter 5 Section 4 Objectives • Describe how carbon atoms bond covalently to form organic compounds. • Identify the names and structures of groups of simple organic compounds and polymers. • Identify what makes up the polymers that are essential to life. Organic Compounds • In chemistry, the word organic is used to describe certain compounds. • An organic compound is a covalently bonded compound that contains carbon, excluding carbonates and oxides. • Many ingredients of familiar substances contain carbon. • Carbon atoms form four covalent bonds in organic compounds. • When a compound is made of only carbon and hydrogen atoms, it is called a hydrocarbon. • Alkanes are hydrocarbons that have only single covalent bonds. • • Examples: The carbon atoms in any alkane with more than three carbon atoms can have more than one possible arrangement. • Carbon atom chains may be branched or unbranched, and they can even form rings. • Except for cyclic alkanes, the chemical formulas for alkanes follow a special pattern. The number of hydrogen atoms is always two more than twice the number of carbon atoms. • Alkenes are hydrocarbons that contain double carbon-carbon bonds. • • Alcohols have hydroxyl, or –OH, groups. • • Example: polyethene (often known as polyethylene) is a long chain made from many molecules of ethene. Some polymers are natural; others are man-made. • • Alcohols, which have the suffix -ol in their names, are found in many household products. A polymer is large molecule that is formed by more than five monomers, or small units. • • Example: methanol, CH3OH Alcohol molecules behave similarly to water molecules. • • Example: ethene, Examples: rubber, starch, protein, and DNA are all natural polymers. Plastics and synthetic fibers are man-made polymers. The elasticity of a polymer is determined by its structure. • Examples: • A milk jug made of polyethene is not elastic: it can be crushed, but does not return to its original shape. • A rubber band is an elastic polymer: when it is stretched and released, it returns to its original shape. Biochemical Compounds • A carbohydate is any organic compound that is made of carbon, hydrogen, and oxygen and that provides nutrients to the cells of living things. • A protein is an organic compound that is a polymer of amino acids, and a principal component of all cells. • An amino acid is any one of 20 different organic molecules that contain a carboxyl and an amino group. • Your DNA determines your entire genetic makeup. • DNA is a polymer with a complex structure. It is in the form of paired strands, in the shape of a twisted ladder known as a double helix. • Each time a new cell is made in your body, a new copy of your DNA is made for the new cell. • The two strands in the helix are separated each time your DNA is copied.