C11 introduction to organic chemistry

• organic molecules can be represented by different types of formulae
• empirical formula is the simplest integer ratio of the atoms of each element in a molecule
• when empirical formula is multiplied by a factor it is equal to the molecular formula
• molecular formula is the actual number of atoms of each element in a molecule
• molecular formula is a multiple of empirical formula
• displayed formula shows every bond and atom in a molecule, using single/double/triple lines to represent single/double/triple bonds, and the chemical symbol of each element to show atoms
• structural formula shows the arrangement of atoms in a molecule, without showing all of the bonds, chemical symbols of elements are used to show atoms, branches are shown using brackets
• skeletal formula shows all of the bonds and atoms except hydrogen atoms, carbon atoms, and C-H bonds, every carbon is assumed to make 4 bonds so any missing bonds mean a C-H bond, lines represent C-C bonds
• 3D structural formula shows the 3D shape of a molecule, bonds coming out of the paper are shown by wedges, bonds going into the paper are shown by dotted lines, other bonds are shown with solid lines
• general formula is the pattern of atoms in the same homologous series
• curly arrows are used in mechanisms to show the movement of electrons
• curly arrows typically go from a lone pair or covalent bond to a positively charged area, because electrons are negatively charged so attracted to positive charges
• free radicals are fragments of a molecule when a covalent bond is broken which have an unpaired electron
• free radicals are shown by a dot and are typically very reactive
• to name organic compounds, use IUPAC rules
• a IUPAC name has a root which represents the longest unbranched hydrocarbon chain or ring

  1 = meth- 2 = eth- 3 = prop- 4 = but- 5 = pent- 6 = hex-
• in a IUPAC name, the syllable after the root represents whether there are any double bonds

  -ane = no double bonds -ene = double bonds
• in a IUPAC name, side chains are shown by a prefix

  CH3 = methyl- C2H5 = ethyl- C3H7 = propyl- C4H9 = butyl-
• in a IUPAC name, hydrocarbon rings have the additional prefix cyclo-
• in a IUPAC name, functional groups are represented by a suffix or prefix

  alkane = -ane

  alkene = -ene

  alcohol = -ol

  ketone = -one

  halogenoalkane = bromo-/chloro-/fluoro-/iodo-

  aldehyde = -al

  carboxylic acid = oic acid
• a homologous series is a family of organic compounds with the same functional group, but different carbon chain lengths
• members of a homologous series have a general formula
• each member of the series differs from the next by CH2 but the length of the carbon chain has little effect on the reactivity of the compounds, however it does affect the physical properties of the compounds such as melting point, boiling point and solubility
• isomers are molecules which have the same molecular formula but their atoms are arranged differently
• the two basic types of isomerism are structural isomerism and stereoisomerism
• structural isomerism is when molecules have the same molecular formula but different structural formulae
• the three types of structural isomerism are positional isomerism, functional group isomerism, and chain isomerism
• in positional isomerism, the same functional group is attached to the chain at different points
• in functional group isomerism, the functional group changes but is at the same point
• in chain isomerism, the hydrocarbon chain is arranged differently, such as different branches
• stereoisomerism is when molecules have the same structural formula but a different arrangement of atoms in space
• the two types of stereoisomerism are E-Z isomerism and optical isomerism
• E-Z isomerism is when substituents are either together, Z, or on opposite side, E, of the double bond, as there is no rotation around the double bond
• cahn-ingold-prelog rules state that for E-Z isomerism, the atom or group with the greater Mr or Ar is given priority, and is used to determine whether it is the E or Z isomer