Chapter 24: Organic Compounds

Section 1: Simple Organic Compounds

• Organic Compounds

  • Most compounds containing the element carbon
  • A carbon atom has four electrons in its outer energy level
  • Another reason carbon can form so many compounds is that carbon can link together with other carbon atoms in many different arrangements—chains, branched chains, and even rings.
  • Hydrocarbon: A compound made up of only carbon and hydrogen atoms

• Carbon forms an enormous number of compounds with hydrogen alone.

• The structural formula uses lines to show that four hydrogen atoms are bonded to one carbon atom in a methane molecule.

• The space-filling model, shows a more realistic picture of the relative size and arrangement of the atoms in the molecule.

• Methane and other hydrocarbons produce more than 90 percent of the energy humans use.

• Single Bonds

  • In some hydrocarbons, the carbon atoms are joined by single covalent bonds.
  • Saturated Hydrocarbons: Hydrocarbons containing only single-bonded carbon atoms.
  • The chemical formula of butane is C4H10. Another hydrocarbon called isobutane has exactly the same chemical formula.
  • Boiling points of hydrocarbons increase as the

  number of carbon atoms in the chain increases.

  • Isomers: compounds that have identical chemical formulas but different molecular structures and shapes.
  • Thousands of isomers exist among the hydrocarbons.
  • Some isomers differ only slightly in how their atoms are arranged in space.

• Multiple Bonds

  • Ethylene is another name for the hydrocarbon ethene, C2H4. This contains one double bond in which two carbon atoms share two pairs of electrons.
  • Unsaturated Hydrocarbons: Hydrocarbons, such as ethene and ethyne, that contain at least one double or triple bond.

Section 2: Other Organic Compounds

• Aromatic Compounds
  • Many chemical compounds produce pleasant odors but others have less pleasant flavors and smells.
  • Aromatic Compound: one that contains a benzene structure having a ring with six carbons.
  • Many known compounds contain three or more rings fused together.
• Substituted Hydrocarbons: changed compounds
  • Chemists change hydrocarbons into other compounds having different physical and chemical properties.
  • A substituted hydrocarbon has one or more of its hydrogen atoms replaced by atoms or groups of other elements.
  • Alcohol: formed when –OH groups replace one or more hydrogen atoms in a hydrocarbon.
  • Organic acids form when a carboxyl group, –COOH, is substituted for one of the hydrogen atoms attached to a carbon atom.
  • Other atoms besides hydrogen and oxygen can be added to hydrocarbons. One is chlorine.
  • When sulfur replaces oxygen in the –OH group of an alcohol, the resulting compound is called a thiol, or more commonly a mercaptan.

Section 3: Petroleum—A Source of Carbon Compounds

• What is petroleum?

  • Petroleum—a dark, flammable liquid, often called crude oil, that is found deep within Earth.
  • Like coal and natural gas, this dark, foul-smelling substance is formed from the remains of

  fossilized material.

  • The separation process is known as fractional distillation.
  • The tower separates crude oil into fractions containing compounds having a range of boiling points.
  • The higher boiling fractions reach only the lower plates before they condense, forming shallow pools that drain off through pipes on the sides of the tower and are collected.
  • The separation of the fractions is improved by the inter- action of rising vapors with condensed liquid. The processes involved vary.

• Uses for Petroleum Compounds

  • The fractions that condense on the upper plates and contain from five to ten carbons are used for gasoline and solvents.
  • Some fractions are used directly for fuel—the lightest fractions from the top of the tower include butane and propane.

• Polymers: Extremely large molecules

  • Monomer: small molecule, which forms a link in the polymer chain
  • One common polymer or plastic is made from the monomer ethene or ethylene.
  • Polyethylene: ethylene combines with itself repeatedly.
  • Polymers can be made light and flexible or so strong that they can be used to make plastic pipes, boats, and even some auto bodies.
  • The properties of polymers depend mostly on which monomers are used to make them.
  • Polymer materials can be shaped in many ways.
  • Sometimes the same polymer can take two completely different forms.
  • Other polymers can be spun into threads, which are used to make clothing or items such as suitcases and backpacks.
  • The first synthetic dye was a bright purple called mauve that was discovered accidentally in coal tar compounds.
  • Polymers have been used so widely that disposal has caused problems, because many polymers do not decompose.
  • Depolymerization: uses heat or chemicals to break the long polymer chain into its monomer fragments.

Section 4: Biological Compounds

• Biological Polymers
  • Like the polymers that are used to make the plastics and fibers, biological polymers are huge molecules.
  • Many of the important biological compounds in your body are polymers. Among them are the proteins, which often contain hundreds of units.
• Proteins: large organic polymers formed from organic monomers called amino acids.
  • Amino acids are the monomers that combine to form proteins.
  • Amine groups of one amino acid can combine with the carboxylic acid group of another amino acid, linking them together to form a compound called a peptide.
  • Long protein molecules tend to twist and coil in a manner unique to each protein.
  • When you eat foods that contain proteins, such as meat, dairy products, and some vegetables, your body breaks down the proteins into their amino acid monomers.
• Nucleic Acids: another important group of organic polymers that are essential for life.
• Deoxyribonucleic Acid: or DNA, is found in cells where it codes and stores genetic information. This is known as the genetic code.
  • The monomers that make up DNA are called nucleotides. A nucleotide is a complex molecule that contains one of four organic bases, a sugar, and a phosphate unit.
  • Human DNA contains more than 5-billion base pairs.
  • The DNA of each person differs in some way from that of everyone else, except for identical twins, who share the same DNA sequence.
• Carbohydrates: compounds containing carbon, hydrogen, and oxygen, that have twice as many hydrogen atoms as oxygen atoms.
  • Sugars are a major group of carbohydrates.
  • The sugar glucose is found in your blood and also in many sweet foods such as grapes and honey. Starch is a carbohydrate that is also a polymer.
  • It is made of units or monomers of the sugar glucose.
• Lipids: Fats, oils, and related compounds make up a group of organic compounds
  • Lipids include animal fats such as butter, and vegetable oils such as corn oil.
  • Saturated fats contain only single bonds between carbon atoms.
• Unsaturated fats having one double bond are called monounsaturated, and those having two or more double bonds are called polyunsaturated.
  • Plant lipids called oils are unsaturated and are usually liquids.
  • It appears that saturated fats are more likely to be converted to substances that can block the arteries leading to the heart.
  • Cholesterol is another lipid that is often in the news. It is found in meats, eggs, butter, cheese, and fish.