12'1 Alkanes

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Chapter 12 Alkanes

• 12.1 Alkanes

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Alkanes

• Alkanes
• Contain only C and H.
• Have only single CC bonds.
• Have a general formula of CnH2n 2.
• C Atoms H Atoms Formula
• 1 2(1) 2 4 CH4
• 3 2(3) 2 8 C3H8
• 6 2(6) 2 14 C6H14

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Structural Formulas

• Structural formulas show the arrangement of
• atoms in an organic compound.
• In expanded structural formulas, all the
  individual bonds are drawn.
• In condensed structural formulas, each carbon is
  written with the H atoms connected to it.
• H H
• HC CH3 C CH2
• H H

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Line-Bond Formulas

• Because each C atom has a tetrahedral
  arrangement, the geometrical arrangement of
  carbon atoms is not a straight line.
• A line-bond formula abbreviates the carbon chain
  and shows only the zigzag pattern of bonds from
  carbon atom to carbon atom.

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Summary of Formulas

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IUPAC System of Naming Alkanes

• The IUPAC (International Union of Pure and
  Applied Chemistry) establishes the rules for
  naming organic compounds.
• Alkanes are named with ane endings.
• The first four alkanes are methane, ethane,
  propane, and butane.
• The names of longer carbon chains use Greek
  prefixes such as pent- for 5 C atoms and hex- for
  6 C atoms.

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Names of Continuous-Chain Alkanes
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Conformations

• As the groups attached to a C-C single bond
  rotate around the bond, their relative
  arrangements has different conformations.

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Conformations of Butane

• Rotation of the end CH3- provides different
  conformations for butane.

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Drawing Structures for Butane