Organic Molecules

• Define organic molecules as molecules containing carbon atoms.

Organic molecular structures – functional groups, saturated and unsaturated structures, isomers

• Write down condensed structural formulae, structural formulae and molecular formulae (up to 8 carbon atoms, one functional group per molecule) for:
  • Alkanes (no ring structures)
  • Alkenes (no ring structures)
  • Alkynes
  • Halo-alkanes (primary, secondary and tertiary haloalkanes; no ring structures)
  • Alcohols (primary, secondary and tertiary alcohols)
  • Carboxylic acids
  • Esters
  • Aldehydes
  • Ketones
• Know the following definitions/terms:
  • Molecular formula:
    A chemical formula that indicates the type of atoms and the correct number of each in a molecule.
    Example: C₄H₈O
    
  • Structural formula:
    A structural formula of a compound shows which atoms are attached to which within the molecule. Atoms are represented by their chemical symbols and lines are used to represent ALL the bonds that hold the atoms together.
    Example:
    
  • Condensed structural formula:
    This notation shows the way in which atoms are bonded together in the molecule, but DOES NOT SHOW ALL bond lines.
    Example:
    
    
    OR
    
    
  • Hydrocarbon:
    Organic compounds that consist of hydrogen and carbon only.
  • Homologous series:
    A series of organic compounds that can be described by the same general formula OR in which one member differs from the next with a CH 2 group.
  • Saturated compounds:
    Compounds in which there are no multiple bonds between C atoms in their hydrocarbon chains.
  • Unsaturated compounds:
    Compounds with one or more multiple bonds between C atoms in their hydrocarbon chains.
  • Functional group:
    A bond or an atom or a group of atoms that determine(s) the physical and chemical properties of a group of organic compounds.
    
  • Structural isomer:
    Organic molecules with the same molecular formula, but different structural formulae.
• Identify compounds (up to 8 carbon atoms) that are saturated, unsaturated and are structural isomers.
• Restrict structural isomers to chain isomers, positional isomers and functional isomers.
• Chain isomers:
  Same molecular formula, but different types of chains, e.g. butane and 2-methylpropane.
  
  
  and
  
  


• Positional isomers:
  Same molecular formula, but different positions of the side chain, substituents or functional groups on the parent chain,
  Example 1
  1-choropropane and 2-chloropropane
  
  
  
  and
  
  
  
  Example 2
  but-2-ene and but-1-ene
  
  
  
  and
  
  


• Functional isomers:
  Same molecular formula, but different functional groups, e.g. methyl methanoate and ethanoic acid.
  
  
  
  and
  
  

IUPAC naming and formulae

• Write down the IUPAC name when given the structural formula or condensed structural formula for compounds from the homologous series above, restricted to one functional group per compound, except for haloalkanes. For haloalkanes, maximum two functional groups per molecule.
• Write down the structural formula when given the IUPAC name for the above homologous series.
• Identify alkyl substituents (methyl- and ethyl-) in a chain to a maximum of THREE alkyl substituents on the parent chain.
• When naming haloalkanes, the halogen atoms do not get preference over alkyl groups – numbering should start from the end nearest to the first substituent, either the alkyl group or the halogen. In haloalkanes, where e.g. a Br and a Cℓ have the same number when numbered from different ends of chain, Br gets alphabetical preference.
• When writing IUPAC names, substituents appear as prefixes written alphabetically (bromo, chloro, ethyl, methyl), ignoring the prefixes di- and tri.

Structure and physical properties (boiling point, melting point, vapour pressure) relationships

• For a given example (from the above functional groups), explain the relationship between physical properties and:
  
  • Strength of intermolecular forces (Van der Waal's forces), i.e. hydrogen bonds, dipole-dipole forces, induced dipole forces
  • Type of functional groups
  • Chain length
  • Branched chains

Oxidation of alkanes

• State the use of alkanes as fuels.
• Write down an equation for the combustion of an alkane in excess oxygen.

Esterification

• Write down an equation, using structural formulae, for the formation of an ester.
• Name the alcohol and carboxylic acid used and the ester formed.
• Write down reaction conditions for esterification.

Substitution, addition and elimination reactions

• Identify reactions as elimination, substitution or addition.
• Write down, using structural formulae, equations and reaction conditions for the following addition reactions of alkenes:
  • Hydrohalogenation:
    The addition of a hydrogen halide to an alkene
  • Halogenation:
    The reaction of a halogen (Br₂ , Cℓ₂) with a compound
  • Hydration:
    The addition of water to a compound
  • Hydrogenation:
    The addition of hydrogen to an alkene
• Write down, using structural formulae, equations and reaction conditions for the following elimination reactions:
  • Dehydrohalogenation of haloalkanes:
    The elimination of hydrogen and a halogen from a haloalkane
  • Dehydration of alcohols:
    Elimination of water from an alcohol
  • Cracking of alkanes:
    The chemical process in which longer chain hydrocarbon molecules are broken down to shorter more useful molecules.
• Write down, using structural formulae, equations and reaction conditions for the following substitution reactions:
  • Hydrolysis of haloalkanes
    Hydrolysis: The reaction of a compound with water
  • Reactions of HX (X = Cℓ, Br) with alcohols to produce haloalkanes
  • Halogenation of alkanes
    The reaction of a halogen (Br₂ , Cℓ₂) with a compound
• Distinguish between saturated and unsaturated hydrocarbons using bromine water.

Plastics and polymers (ONLY BASIC POLYMERISATION as application of organic chemistry)

• Describe the following terms:
  • Macromolecule: A molecule that consists of a large number of atoms
  • Polymer: A large molecule composed of smaller monomer units covalently bonded to each other in a repeating pattern
  • Monomer: Small organic molecules that can be covalently bonded to each other in a repeating pattern
  • Polymerisation: A chemical reaction in which monomer molecules join to form a polymer
• Distinguish between addition polymerisation and condensation polymerisation:
  • Addition polymerisation: A reaction in which small molecules join to form very large molecules by adding on double bonds
  • Addition polymer: A polymer formed when monomers (usually containing a double bond) combine through an addition reaction
  • Condensation polymerisation: Molecules of two monomers with different functional groups undergo condensation reactions with the loss of small molecules, usually water
  • Condensation polymer: A polymer formed by two monomers with different functional groups that are linked together in a condensation reaction in which a small molecule, usually water, is lost
• Identify monomers from given addition polymers.
• Write down an equation for the polymerisation of ethene to produce polythene.
• State the industrial uses of polythene.