Org chem

• Topics to discuss


  • Nomenclature
  • Physical properties
  • Sources
  • Uses
  • Preparation
  • Analysis
  • Reactions
  • Mechanisms
  • Simple multi-step synthesis
• Functional groups


  Specific atoms bonded in a certain arrangement that give a compound certain physical and chemical properties
• Role of functional groups in organic chemistry

  • Responsible for the characteristic chemical reactions of a compound
  • The same functional group will behave in a similar fashion, by undergoing similar reactions, regardless of the compound of which it is a part
  • Play an important part in organic compound nomenclature
• Alpha carbon


  The first carbon atom that attaches to the functional group
• Beta carbon


  The second carbon atom that attaches to the functional group
• Gamma carbon


  The third carbon atom that attaches to the functional group
• Primary, secondary, tertiary functional group

  Depending on if it is attached to one, two, or three carbon atoms
• Common functional groups


  • Carbonyls (C=O)
  • Alcohols (-OH)
  • Carboxylic acids (CO2H)
  • Esters (CO2R)
  • Amines (NH2)
• It is important to be able to recognize the functional groups and the physical and chemical properties that they afford compounds
• Hydrocarbons are the simplest organic compounds, containing only carbon and hydrogen
• Hydrocarbons provide the scaffolding on which more reactive functional groups are attached
• There is a wide variety of hydrocarbons because they may consist of varying lengths of chains, branched chains, and rings of carbon atoms, or combinations of these structures
• Many hydrocarbons are found in plants, animals, and their fossils; other hydrocarbons are used everyday, mainly as fuels
• Familiar plastics like polyethylene, polypropylene, and polystyrene are also hydrocarbons
• The system used throughout the world for naming organic compounds is based on a set of rules for naming hydrocarbons, then extending the rules to include compounds that contain functional groups
• Today polymers have influenced our lifestyle to the extent that it would not be wrong to say that we are in polymer age
• Polymers find wide range of uses starting from common household utensils, automobiles, clothes, furniture, etc., to space-aircraft and biomedical and surgical components
• Boiling points of alkanes


  • Increase smoothly with increasing molecular mass
  • Similar to those of the corresponding alkenes and alkynes because of similarities in molecular mass between analogous structures
• Melting points of alkanes, alkenes, and alkynes

  • Show a much wider variation because the melting point strongly depends on how the molecules stack in the solid state
  • Sensitive to relatively small differences in structure, such as the location of a double bond and whether the molecule is cis or trans
• Alkanes


  • Contain only C-C and C-H bonds, which are strong and not very polar
  • Not easily attacked by nucleophiles or electrophiles
  • Their reactivity is limited, and often their reactions occur only under extreme conditions
• Catalytic cracking


  1. Can be used to convert straight-chain alkanes to highly branched alkanes, which are better fuels for internal combustion engines

  2. An example of a pyrolysis reaction, in which alkanes are heated to a sufficiently high temperatures to induce cleavage of the weakest bonds: the C-C single bonds
• Alkanes


  Saturated hydrocarbons containing only single covalent bonds between carbon atoms
• Properties of alkanes


  • Colourless and odourless
  • Possess weak Van Der Waals forces of attraction
  • Alkanes with 1-4 carbon atoms are gases, 5-17 carbon atoms are liquids, and 18 or more carbon atoms are solids at 298 K
  • All carbon atoms are sp3 hybridized, forming four sigma bonds with either carbon or hydrogen atoms
  • Bond angle between them is 109.5° and they exhibit tetrahedral geometry
• Boiling point of alkanes


  • Increases with increasing molecular weight as the Van Der Waals force increases
  • Straight chain alkanes have a higher boiling point than their structural isomers
• Melting point of alkanes

  • Increases with increasing molecular weight because it is difficult to break the intermolecular forces of attraction between higher alkanes
  • Even-numbered alkanes have a better packing in the solid phase than odd ones, so even-numbered alkanes have higher melting point than odd-numbered
• Solubility of alkanes


  • Generally non-polar molecules due to the covalent bonds between C-C and C-H and the small difference between electronegativities of carbon and hydrogen
  • Insoluble in water or hydrophobic in nature
  • Soluble in organic solvents because the energy required to overcome existing Van Der Waals forces and to generate new Van Der Waals forces is quite comparable
• Density of alkanes


  • Lower than water, so they float on water
  • Increases with an increase in molecular mass
• Apart from weak Van Der Waals forces, London forces, and dipole-dipole interactions, alkanes have no other significant intermolecular forces
• Alkanes


  Saturated hydrocarbons
• Alkanes


  • Non-polar molecules due to covalent C-C and C-H bonds and small electronegativity difference between C and H
  • Insoluble in water/hydrophobic due to non-polarity
  • Soluble in non-polar organic solvents due to comparable energy required to overcome and generate Van der Waals forces
• Density of alkanes


  Lower than water, increases with increase in molecular mass
• Intermolecular forces in alkanes


  • Weak Van der Waals, London, and dispersion forces
• Isomers


  Hydrocarbons with the same formula can have different structures
• Isomers of C4H10


  • n-butane
  • 2-methylpropane (isobutane)
• Organic nomenclature


  • Base name reflects number of carbons in parent chain
  • Suffix reflects type of functional group
  • Substituents are other groups attached to parent chain
• Names of straight-chain alkanes up to 12 carbons

  • methane
  • ethane
  • propane
  • butane
  • pentane
  • hexane
  • heptane
  • octane
  • nonane
  • decane
  • undecane
  • dodecane
• Substituent names


  Formed by changing -ane suffix to -yl
• Common branched substituents


  • methyl
  • ethyl
  • propyl
  • butyl
  • pentyl
  • hexyl
  • heptyl
  • octyl
  • nonyl
  • decyl
  • isopropyl
  • isobutyl
  • sec-butyl
  • tert-butyl
• IUPAC rules for naming alkanes

  1. Identify longest carbon chain as parent chain

  2. Identify all substituents

  3. Number carbons from end giving substituents lowest numbers

  4. Indicate multiple occurrences of same substituent

  5. List substituents in alphabetical order

  6. If chains are equal length, choose based on most/lowest substituents, most C atoms in smaller side chain, least branching
• Cyclic hydrocarbons are designated with prefix "cyclo-"