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1.1: Unbranched Alkanes

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    Learning Objective

    • Naming Unbranched Alkanes (Organic Chemistry)

    An alkane is a type of hydrocarbon (a compound consisting of only carbon and hydrogen atoms). When the carbon-carbon backbone consists only of single bonds, the hydrocarbon contains as many hydrogen atoms as possible, and is therefore saturated. Alkanes are saturated hydrocarbons.

    Figure \(\PageIndex{1}\). Hexane is an unbranched, saturated alkane containing six carbon atoms: Hexane

    Below is a table of the names of unbranched, saturated alkanes containing up to ten carbons, with their condensed structural formulas, molecular formulas, and boiling points.

    Alkane Condensed Structural Formula Molecular Formula Boiling Point (degrees C)
    Methane CH4 CH4 -161
    Ethane CH3CH3 C2H6 -89
    Propane CH3CH2CH3 C3H8 -42
    Butane CH3CH2CH2CH3 -0.5
    Pentane CH3(CH2)3CH3 36
    Hexane CH3(CH2)4CH3 69
    Heptane 98
    Octane 126
    Nonane 151
    Decane 174

    Table of names, condensed structural formulas, molecular formulas, and boiling points of unbranched saturated alkanes containing up to ten carbon atoms.

    Practice Questions

    1. Fill in the blank spaces in the table.
    2. Draw the structures of these ten unbranched alkanes, using Figure \(\PageIndex{1}\) (hexane) as a model.
    3. What do the names of these molecules have in common?
    4. What is the relationship between the number of carbon atoms and the number of hydrogen atoms in an unbranched alkane? Provide a general formula (use n for the number of carbon atoms).
    5. Draw a graph of boiling points versus number of carbon atoms in unbranched alkanes.
    6. How do the boiling points vary with the number of carbons? Propose an explanation for this observation.

    1.1: Unbranched Alkanes is shared under a CC BY license and was authored, remixed, and/or curated by Rebekah O'Donnell.

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