Chemistry 29: Classes of Organic Compounds

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Chemistry 29 Classes of Organic Compounds

• Christopher Chui

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Classification of Hydrocarbons

• Hydrocarbons contain hydrogen and carbon atoms
• Hydrocarbons are classified as aromatic or
  aliphatic
• Alkane is a chain compound with single bond C-C
• A saturated H-C is an alkane with single bond C-C
• Each alkane differs from the next by CH2 group
• Alkanes are also called the paraffin series
• Each member of a homologous series differs from
  each other member by a specific structural unit
• The general formula for alkanes CnH2n2
• CH4 methane, C2H6 ethane, C3H8 propane
• A HC radical is a HC molecule from which a H atom
  removed
• Radicals are named by substituting the yl from
  the -ane

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Naming Branched Alkanes

• CH3- methyl, C2H5- ethyl, C3H7- propyl, C4H9-
  butyl, C5H11- pentyl, C6H13- hexyl, C7H15-
  heptyl, C8H17- octyl, C9H19- nonyl, C10H21- decyl
• Carbon atoms in a structural formula are given
  position numbers, 1, 2, 3, 4, etc
• Alkanes are named on the basis of the longest
  continuous chain of carbon atoms (parent chain)
• Parent chain does not need to be straight
• Substituents or branch chains are attached to the
  main chain of carbon atoms
• Carbons are numbered so as to give the lowest
  position numbers to the branches

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Alkanes Isomers Cycloalkanes

• Isomers have the same formula but different
  molecular structures
• Butane and 2-methylpropane are isomers
• Pentane, 2-methybutane, and 2,2-dimethylpropane
• Cycloalkanes are single-bond ring compounds with
  the general formula CnH2n
• A strained bond results when the molecular
  geometry shows the bonding electrons to be closer
  than the normal 109.5 degrees

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Alkenes and its Naming

• Alkenes are unsaturated hydrocarbon that contain
  double bonds
• General formula for alkenes CnH2n
• A double bond is stronger than a single bond
• Alkene isomers differ in the location of their
  double bonds
• Compounds are named according to the longest
  chain that includes a double bond
• Number the chain so the lowest possible position
  number is assigned to the first double-bonded
  carbon atom
• Geometric isomerism may result from double bonds
• Double bonds are also found in cyclic compounds
• A molecule whose name ends in diene contains 2
  double bonds

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Alkynes Aromatic Hydrocarbons

• Alkynes contain triple bonds and have the general
  formula CnH 2n2
• Alkynes are very reactive
• Number the chain so the lowest possible number is
  assigned to the first triple-bonded carbon atom
• The benzene ring contains a conjugated system of
  bonds
• Aromatic compounds are generally derived from
  benzene
• Naphthalene, C10H8, has a fused ring structure
• The phenyl radical is formed by removing a
  hydrogen atom from a benzene
• Aromatic compounds are economically important to
  many chemical industries such as rubber,
  plastics, fibers, explosives, paint, and
  petroleum

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Halogen Derivatives

• Substitutions in a hydrocarbon generally increase
  the reactivity
• A halogen derivative has a halogen atom
  substituted for a hydrogen atom
• Substituted hydrocarbons are named with the
  lowest possible position numbers for substituents
• Note that the double bond has precedence over the
  halogen when numbering the parent chain
• The halogen-substituted hydrocarbon ethyl
  chloride is often used as a local anesthetic.
  Iodoform is used as an antiseptic

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Organic Oxygen Compounds

• Class alcohol, formula ROH, ending ol
• Class ether, formula ROR, ending oxy-
• Class aldehyde, formula RCOH, ending al
• Class ketone, formula RCOR, ending one
• Class acid, formula RCOOH, -oic acid
• Class ester, formula RCOOR, -yl oate
• Alcohols contain the hydroxyl group, --OH
• Phenol is formed when a hydroxyl group attaches
  to a benzene ring
• Cranberriesbenzoic acid, grapestartaric acid,
  citrus fruitscitric acid, sour milklactic acid,
  rhubarboxalic acid, green applesmalic acid

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Organic Acids

• Organic acids contain the carboxylic acid group
  RCOOH
• Many esters have pleasant odors ethyl
  butyratepineapple, ethyl formaterum, methyl
  butyrateapple, methyl salicylatewintergreen,
  octyl acetateorange, pentyl acetatebanana,
  pentyl butyrateapricot
• Hexanedioic acid (adipic acid) is synthesized
  from cyclohexane in making nylon
• Vinyle acetate is an ester produced from ethyne
  and ethanoic acid to make adhesives and paints

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Organic Nitrogen Compounds

• An amine contains nitrogen bonded to alkyl groups
  and hydrogen atoms
• Amines are Lewis bases since the N atom has an
  unshared pair of electrons
• 3 amines have bad odors putrescine C4H12N2, and
  cadaverine, C5H14N2?bad breath, trimethylamine,
  C3H9N?rotting fish odor
• Amides are characterized by a carbonyl group and
  an amine group
• Nitriles contain a carbon-nitrogen triple bond

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Organic Compounds with Nitrogen

• Class amines, formula RNH2, ethanamine
• Class amides, formula RCONH2, ethanamide
• Class amino acids, formula GCHNH2COOH, alanine
  (2-aminopropanoic acid)
• Class nitriles, formula RCN, butanenitrile
• Class nitro compounds, formula RNO2,
  nitrobenzene
• One important nitrile is propenenitrile,
  manufactured from propene, ammonia, and oxygen to
  make fibers, plastics, and synthetic rubber