Carbon: Not Just Another Element

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Carbon Not Just Another Element

• Chapter 23

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Learning Objectives

• Students understand
• General principles of structure and bonding
  applied to organic compounds
• Why carbon forms a vast array of diverse chemical
  compounds
• Students will be able to
• Classify organic compounds based on formula and
  structure
• Recognize and draw structures of structural
  isomers and stereoisomers for carbon compounds
• Draw structures of molecules, given the name
  and/or the formula, and name organic compounds
  using standard nomenclature rules

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23.1 Why Carbon?

• Organic compounds contain the element carbon,
  which can bond with other carbon atoms to form
  straight chains and branched chains.
• Isomers
• identical composition but linked in different ways

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23.2 Hydrocarbons

• Carbon and hydrogen only
• Alkanes, cycloalkanes
• Alkenes
• Alkynes
• Aromatic compounds

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Alkanes

• Alkanes contain only single bonds between carbon
  atoms.
• Alkanes and other organic compounds are best
  represented by structural formulas and can be
  named using systematic rules determined by the
  International Union of Pure and Applied Chemistry
  (IUPAC).

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Alkanes

• Each alkane has the general formula CnH2n2 n is
  the number of carbon atoms.
• Straight-chain hydrocarbons, also called
  unbranched or normal, all carbon atoms are
  connected in a long chain.
• The name of each alkane ends in the suffix -ane.

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Alkanes

• The root of the name corresponds to the longest
  carbon chain in the compound
• Substituent groups are identified by a name and
  position in the carbon chain
• called alkyl group
• 2 or more of the same alkyl group (use
  di-,tri-tetra-) otherwise list in alphabetical

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Name Formula Name Formula
Methane CH4 Hexane C6H14
Ethane C2H6 Heptane C7H16
Propane C3H8 Octane C8H18
Butane C4H10 Nonane C9H20
Pentane C5H12 Decane C10H22
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Saturated Compounds

• Saturated hydrocarbons have all carbon-carbon
  single bonds.
• Unsaturated hydrocarbons contain carbon-carbon
  multiple bonds.

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Cyclic Alkanes and Alkane Properties

• Alkanes that contain hydrocarbon rings are called
  cyclic alkanes.
• Alkanes are nonpolar compounds that have low
  reactivity and lower melting points and boiling
  points (weak C-C bonds strained hydrocarbons)
  than polar molecules of similar size and mass.

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Alkenes and Alkynes

• Alkenes and alkynes are hydrocarbons that contain
  at least one double or triple bond, respectively.
• Alkenes and alkynes are nonpolar compounds with
  greater reactivity than alkanes but with other
  properties similar to alkanes.

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Alkenes and Alkynes

• Alkenes and alkynes can also be named using IUPAC
  rules.
• Look at the longest chain to figure out the
  parent name.
• Alkenes have the general formula of CnH2n.
• Root ending is -ene
• Alkynes have the general formula of CnH2n-2.
• Root ending is -yne

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Naming Isomers

• Look at the longest continuous chain that
  determines the root name. This is the last part
  of the name.
• Next name the alkyl group that substitutes on the
  parent chain.
• Specify the location of the groups by numbering
  longest chain sequentially.
• hexane vs. 2-methylpentane vs. 2,3
  dimethylbutane vs. 2,2 - dimethylbutane

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Naming Isomers

• Alkenes exhibit cis-trans isomerism because
  rotation around the double bond is restricted.
• In cis isomerism the heavier groups are on the
  same side of the double bond.
• In trans isomerism the heavier groups are on
  opposite sides of the double bond.

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• cis 2-pentene
• trans-2-pentene

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Aromatic Hydrocarbons and Petroleum

• Aromatic hydrocarbons contain benzene rings as
  part of their molecular structures. Nonaromatic
  hydrocarbons are called aliphatic hydrocarbons.
• Extra stability due to resonance stabilization

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Aromatic Hydrocarbons

• May contain two or more benzene rings fused
  together
• Some are carcinogenic
• Major sources are petroleum and natural gas
• Fractional distillation can separate petroleum
  into components

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23.3-23.4 Functional Groups

• Halide
• Alcohol R-OH
• Ether R-O-R
• Aldehyde R-(CO)-H
• Ketone R-(CO)-R
• Carboxylic acid R-(CO)-OH
• Ester R-(CO)-O-R
• Amide R-NH2, R-NHR, R-NRR
• Amine H-NH2, H-NHR, H-NRR