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3: Organic Compounds- Alkanes and Their Stereochemistry

  • Page ID
    31396
  • This chapter begins with an introduction to the concept of the functional group, a concept that facilitates the systematic study of organic chemistry. Next, we introduce the fundamentals of organic nomenclature (i.e., the naming of organic chemicals) through examination of the alkane family of compounds. We then discuss, briefly, the occurrence and properties of alkanes, and end with a description of cis-trans isomerism in cycloalkanes.

    • 3.1: Chapter Objectives
    • 3.2: Functional Groups
      Functional groups are atoms or small groups of atoms (two to four) that exhibit a characteristic reactivity. A particular functional group will almost always display its characteristic chemical behavior when it is present in a compound. Because of their importance in understanding organic chemistry, functional groups have characteristic names that often carry over in the naming of individual compounds incorporating specific groups
    • 3.3: Alkanes and Alkane Isomers
      Alkanes are organic compounds that consist entirely of single-bonded carbon and hydrogen atoms and lack any other functional groups. Alkanes have the general formula CnH2n+2 and can be subdivided into the following three groups: the linear straight-chain alkanes, branched alkanes, and cycloalkanes. Alkanes are also saturated hydrocarbons. Cycloalkanes are cyclic hydrocarbons, meaning that the carbons of the molecule are arranged in the form of a ring.
    • 3.4: Alkyl Groups
      The IUPAC system requires first that we have names for simple unbranched chains, as noted above, and second that we have names for simple alkyl groups that may be attached to the chains. Examples of some common alkyl groups are given in the following table. Note that the "ane" suffix is replaced by "yl" in naming groups. The symbol R is used to designate a generic (unspecified) alkyl group.
    • 3.5: Naming Alkanes
      There are too many organic molecules to memorize a name for each one.  The IUPAC nomenclature system provides an unique name for each different molecule based on functional groups, the longest carbon chain and other attached substituents.
    • 3.6: Properties of Alkanes
      Alkanes are not very reactive and have little biological activity; all alkanes are colorless and odorless.
    • 3.7: Conformations of Ethane
      Conformational isomerism involves rotation about sigma bonds, and does not involve any differences in the connectivity or geometry of bonding. Two or more structures that are categorized as conformational isomers, or conformers, are really just two of the exact same molecule that differ only in terms of the angle about one or more sigma bonds.
    • 3.8: Conformations of Other Alkanes
      Ethane has only two conformers of note - staggered and eclipsed.  Alkanes that are more complex than ethane, like propane and butane have a greater variety in possible conformers and their relative energies.
    • 3.9: Gasoline - A Deeper Look
      The petroleum that is pumped out of the ground at locations around the world is a complex mixture of several thousand organic compounds, including straight-chain alkanes, cycloalkanes, alkenes, and aromatic hydrocarbons with four to several hundred carbon atoms. The identities and relative abundances of the components vary depending on the source.
    • 3.S: Organic Compounds- Alkanes and Their Stereochemistry (Summary)