Organic chemistry

• Alkanes are saturated hydrocarbons lacking any double or triple bonds.
• Reasons for tetravalence of carbon and shapes of organic molecules
• Structures of organic molecules can be written in various ways
• Organic compounds can be classified
• Compounds can be named according to IUPAC system of nomenclature and structures derived from names
• Understanding of organic reaction mechanism
• Influence of electronic displacements on structure and reactivity of organic compounds
• Recognition of types of organic reactions
• Techniques of purification of organic compounds
• Chemical reactions involved in qualitative analysis of organic compounds
• Principles involved in quantitative analysis of organic compounds
• Element carbon exhibits catenation forming covalent bonds with other carbon atoms and atoms of other elements
• Organic compounds studied under a separate branch of chemistry called organic chemistry
• Organic compounds are vital for sustaining life and have various applications in materials like clothing, fuels, polymers, dyes, and medicines
• Organic chemistry is about two hundred years old and distinguishes between organic and inorganic compounds
• Synthesis of organic compounds from inorganic sources in a laboratory by chemists like Wohler, Kolbe, and Berthelot
• Development of electronic theory of covalent bonding influenced modern organic chemistry
• Tetravalence of carbon and formation of covalent bonds explained by electronic configuration and hybridisation of s and p orbitals
• Hybridisation influences bond length and bond enthalpy in organic compounds
• Shapes of molecules like methane, ethene, and ethyne explained by the use of sp3, sp2, and sp hybrid orbitals by carbon atoms
• π bonds provide reactive centers in molecules containing multiple bonds
• Representation of organic compound structures in Lewis, condensed, and bond-line formulas
• Three-dimensional representation of organic molecules using solid and dashed wedge formulas
• Molecular models like framework model, ball-and-stick model, and space filling model used for visualisation of organic molecules
• Classification of organic compounds into acyclic or open chain compounds (aliphatic compounds) and cyclic compounds
• Organic compounds are broadly classified as:

  • Acyclic or open chain compounds (aliphatic compounds)
  • Consist of straight or branched chain compounds
  • Sometimes atoms other than carbon are present in the ring (heterocyclic)
  • Examples include: Cyclopropane, Cyclohexane, Cyclohexene, Tetrahydrofuran
  • Exhibit properties similar to those of aliphatic compounds
• Aromatic compounds are special types of compounds

  • Include benzene and other related ring compounds (benzenoid)
  • Aromatic compounds may also have hetero atom in the ring, called heterocyclic aromatic compounds
  • Examples of aromatic compounds include: Benzene, Aniline, Naphthalene, Tropolone, Isobutane, Acetaldehyde, Acetic acid
• Alicyclic or closed chain or ring compounds contain carbon atoms joined in the form of a ring

  • Examples include: Furan, Thiophene, Pyridine
• Organic compounds can be classified on the basis of functional groups into families or homologous series

  • Functional group: responsible for characteristic chemical properties of organic compounds
  • Examples of functional groups: hydroxyl group (–OH), aldehyde group (–CHO), carboxylic acid group (–COOH)
  • Homologous series: group of organic compounds containing a characteristic functional group
  • Members of a homologous series differ from each other in molecular formula by a –CH2 unit
• • Examples of homologous series: alkanes, alkenes, alkynes, haloalkanes, alkanols, alkanals, alkanones, alkanoic acids, amines
• IUPAC (International Union of Pure and Applied Chemistry) system of nomenclature is used to name organic compounds systematically

  • Names are correlated with the structure for clear identification
  • Organic compounds were traditionally named based on origin or properties, known as trivial or common names
  • Common names are still used when systematic names are lengthy or complicated
• Hydrocarbons are compounds containing carbon and hydrogen only

  • Saturated hydrocarbons contain only carbon-carbon single bonds
  • IUPAC name for a homologous series of saturated hydrocarbons is alkane
  • Unsaturated hydrocarbons contain at least one carbon-carbon double or triple bond
• IUPAC Nomenclature of Alkanes:

  • Straight chain hydrocarbons end with suffix ‘-ane’
  • Names based on chain structure and number of carbon atoms in the chain
  • Branched chain hydrocarbons have small chains of carbon atoms attached to the parent chain
  • Alkyl groups are derived from saturated hydrocarbons by removing a hydrogen atom from carbon
  • Alkyl groups are named by substituting ‘yl’ for ‘ane’ in the corresponding alkane
• Nomenclature of Branched Chain Alkanes:

  • Longest carbon chain in the molecule is identified as the parent chain
  • Carbon atoms of the parent chain are numbered to identify the parent alkane and locate positions of branching
  • Names of alkyl groups attached as a branch are prefixed to the name of the parent alkane
  • Position of substituents is indicated by appropriate numbers
• Cyclic Compounds:

  • Saturated monocyclic compound named by prefixing ‘cyclo’ to the corresponding straight chain alkane
  • If side chains are present, rules for naming branched chain compounds are applied
• Functional group: atom or group of atoms responsible for chemical reactivity in an organic molecule

  • Compounds having the same functional group undergo similar reactions
  • Enables systematisation of organic compounds into different classes
• Functional groups determine the choice of appropriate suffix in compound names
• Longest chain of carbon atoms containing the functional group is numbered so that it is attached at the carbon atom with the lowest possible number
• In polyfunctional compounds, one functional group is chosen as the principal functional group for naming purposes
• Order of decreasing priority for some functional groups: -COOH, –SO3H, -COOR (R=alkyl group), COCl, -CONH2, -CN,-HC=O, >C=O, -OH, -NH2, >C=C<, -C ≡ ≡ ≡ ≡ ≡ C-