CHAPTER 25 - CARBON AND ITS COMPOUNDS

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CHAPTER 25 - CARBON AND ITS COMPOUNDS
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• Organic - pertaining to life
• Living or was once living
• Organic Chemistry - The chemistry of carbon
  compounds
• Carbon is well suited for life because it is the
  most versatile element in terms of bonding.

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Carbon can form four bonds.

• They can be single, double or triple bonds.
• Carbon will not form diatomic molecules like
  other small atoms do.
• It can form long carbon chains containing strong,
  short, covalent bonds.

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Allotropes

• forms of the same element that differ in their
  bonding
• There are several allotropes of carbon
• Diamond tetrahedral network of carbon atoms
  (every atom is locked into place (hardness)
• Graphite sheets can slide over each other
  (lubricant)

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• Amorphous carbon charcoal, soot, coke
• Amorphous has not set arrangement of atoms. It
  has irregular patterns of high surface area, deep
  caves that can trap other molecules
• Fullerenes spherical molecules (60 atoms) see
  page 807, mostly experimental at this point.

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Hydrocarbons

• molecules that contain only hydrogen and carbon

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Fossil Fuels

• Natural gas - mostly methane
• Crude oil - mixture of hydrocarbon chains from
  propane to butane, octane and longer
  Components separated using fractional
  distillation (see page 823)
• Coal - mostly impure carbon (coke - pure carbon
  from coal, charcoal - pure carbon from wood)

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Types of Formulas (examples) Compound - hexane

• Empirical formula
• Molecular formula
• Structural formula
• Condensed structural formula

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CLASSIFICATION OF ORGANIC COMPOUNDS

• ALKANES - Compounds that contain only hydrogen
  and single bonded carbons. (carbon chains
  surrounded by hydrogens)
• Named with an ane ending that is preceded with a
  prefix which gives how many carbons that are in
  the carbon chain.
• Memorize the IUPAC prefixes on page 816

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BRANCHED ALKANES

• Give the name of the branch with a yl ending.
• Indicate the number of the branch (keep numbers
  as low as possible).
• Examples
• Problem assignment 1 (first side of sheet)

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ALKANES SUBSTITUDED WITH HALOGENS

• Give the position of the halogen (F, Cl, Br, or
  I) and then give the name of the halogen with an
  "o" ending.
• 3-chloro-2-methylpentane
• bromochloroiodomethane

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Conformational isomers - molecules with the same
structure but with different bond rotation.

• Molecules with single bonds can rotate about the
  single bond.
• These are the same compound. They have the same
  melting point, the same boiling points and the
  same chemistry.
• The higher the temperature the faster they
  change back and forth from one form to the
  other.
• Example cyclohexane (chair and boat
  conformation)

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• http//www.chem.ucalgary.ca/courses/351/Carey5th/C
  h03/ch3-06.html

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• Structural isomers - molecules that have the same
  molecular formula but have different structural
  formulas.
• These are different compounds with different
  melting points and different chemistry
• Examples C5H12 (pentane, 1 methyl butane, 2,2
  dimethyl propane)

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SUBSTITUTED ALKANES

• Fisher Projection - a way to show the
  3-dementional character of a molecule.
• Examples CHFClI
• A carbon that has 4 different groups bonded to
  it is called a chiral carbon.
• Enantiomers - (mirror image isomers) - two
  arrangements around a chiral carbon that cannot
  be rotated in such a way as to be superimposed on
  each other.

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• They are different molecules that have the
  same formula, same boiling points and much of
  the same chemistry.
• Their chemistry differs when they are
  reacting with molecules that also have chiral
  carbons. (biological systems)
• They also rotate polarized light in opposite
  directions.
• Vitamin C is an example of this type of
  molecule.

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UNSATURATED HYDROCARBONS

• If the molecule is filled to capacity with
  hydrogen the compound is saturated (alkanes).
• If the molecule is cyclic, contains a double
  bond or contains a triple bond it is
  unsaturated.
• Saturated fats are from animals and are not
  good for you.
• Unsaturated fats are from plants.

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• Alkenes - contains a double bond.
• Alkynes - contains a triple bond.
• Use the same prefixes along with a number to give
  the position of the double or triple bond.
• Example 1 propene, 1 propyne, 3
  chloro 1 butene, 3 chloro 1 butyne

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Hybridization and resonance

• A double bonded carbon has 3 groups around it
  (sp2 hybridization)
• Two of the p orbitals combine with the s orbital
  to form three sp2 hybrid orbitals.
• The remaining p orbital is left unchanged and
  lies perpendicular to the flat molecule.
• The overlap of the p orbitals forms a pi bond.
• Sigma bond is the direct overlap of hybrid
  orbitals

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• http//www.mhhe.com/physsci/chemistry/animations/c
  hang_7e_esp/bom5s2_6.swf
• Resonance is when several pi bonds lie in the
  same plane and all overlap
• A pattern of alternating single and double bonds
  results in resonance.
• Examples 1,3 pentadiene, benzene (1,3,5
  cyclohexatriene)