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12.1: Nomenclature and Physical Properties of Cycloalkanes

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    The nomenclature and physical properties of cycloalkanes covers the the IUPAC systems of naming cycloalkanes. The physical properties of cycloalkanes can explain each cycloalkane molecular structure and the relative size from simple propane to multiple carbon containing cycloakane like cyclononane.

    For a review, cycloalkanes contain rings of of carbon atoms linked together by a single bonds. The simple cycloalkanes of formula \(\ce{(CH_2)}_n\) make up a particularly homologous series in which the chemical properties change in a much more dramatic way with increasing \(n\) than do those of the acyclic hydrocarbons \(\ce{CH_3(CH_2)}_{n-1}\ce{H}\). The cycloalkanes with small rings (\(n=3\)-\(6\)) are of special interest in exhibiting chemical properties intermediate between those of alkanes and alkenes. In this chapter we will show how this behavior can be explained in terms of angle strain and steric hindrance, concepts that have been introduced previously and will be used with increasing frequency as we proceed further.

    The IUPAC system for naming cycloalkanes and cycloalkenes was presented in some detail in Sections 3-2 and 3-3, and you may wish to review that material before proceeding further. Additional procedures are required for naming polycyclic compounds, which have rings with common carbons, and these will be discussed later in this chapter. Furthermore, given below are the table of physical properties of cycloalkanes from propane to cyclononane.

    Table 12-1: Physical Properties of Alkanes and Cycloalkanes
    Compounds Boiling Point \(^oC\) Melting Point \(^oC\) Density (g/ml)
    propane -42 -187 0.580
    cyclopropane -33 -127 0.689
    butane -0.5 -135 0.579
    cyclobutane 13 -90 0.689
    pentane 36 -130 0.626
    cyclopentane 49 -94 0.746
    hexane 69 -95 0.659
    cyclohexane 81 7 0.778
    heptane 98 -91 0.684
    cycloheptane 119 -8 0.810
    octane 126 -57 0.703
    cyclooctane 151 15 0.830
    nonane 151 -54 0.718
    cyclononane 178 11 0.845

    The melting and boiling points of cycloalkanes (Table 12-1) are somewhat higher than those of the corresponding alkanes. In contrast to the more rigid cyclic compounds, the general “floppiness” of open-chain hydrocarbons makes them harder to fit into a crystal lattice (hence their lower melting points) and less hospitable toward neighboring molecules of the same type (hence their lower boiling points). The nomenclature and physical properties of cycloalkanes also includes conformation of cycloalkanes, especially cyclohexane in later discussion because of their importance to the chemistry of many kinds of naturally occurring organic compounds. The nomenclature and physical properties of cycloalkanes will also cover polycyclic compounds, substances with more than one ring, and to the cycloalkenes and cycloalkynes.

    Contributors and Attributions

    John D. Robert and Marjorie C. Caserio (1977) Basic Principles of Organic Chemistry, second edition. W. A. Benjamin, Inc. , Menlo Park, CA. ISBN 0-8053-8329-8. This content is copyrighted under the following conditions, "You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format."

    This page titled 12.1: Nomenclature and Physical Properties of Cycloalkanes is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by John D. Roberts and Marjorie C. Caserio.