organic chemistry

• Alkenes are organic compounds that contain a carbon-carbon double bond.
• Kossel and Lewis provided the explanation of valence based on the inertness of noble gases, which have a tendency to attain the noble gas configuration
• Valency is the combining capacity of an atom of an element. For example, H = 1, O = 2, etc.
• Lewis imagined the atom as having a positively charged "Kernel" (nucleus + inner shell electrons) and an outer shell with a maximum accommodation capacity of 8 electrons (octet)
• The octet of electrons in the outer shell represents a state of electronic arrangement
• Lewis postulated that atoms achieve a stable octet when they are linked by chemical bonds
• Noble gases like neon, argon, etc., with 8 electrons in their outermost shell, do not tend to take part in chemical combinations
• Chemical bonds are formed by either the transfer of electrons (as in the formation of NaCl) or the sharing of electrons between two atoms (as in the case of H2, F2, O2, etc.)
• During the formation of chemical bonds, each atom attains a stable octet configuration in their outermost shell (valence shell)
• Organic compounds are classified as either inorganic or organic based on their origin
• Organic chemistry is the branch of chemistry that studies carbon compounds
• Vital force theory proposed by Berzelius suggested that organic compounds could only be produced by a mysterious force in living matter
• Friedrich Wohler accidentally prepared urea in 1828, disproving the vital force theory
• Organic compounds may contain elements like nitrogen, oxygen, sulphur, phosphorus, and halogens in addition to carbon and hydrogen
• Catenation is the self-linking property of an atom to bond with the same atoms to form long chains, branches, or rings
• Carbon shows maximum catenation, allowing for the formation of numerous compounds
• Carbon atoms can form straight chains, branched chains, and ring structures due to catenation
• Hybridization is the mixing of orbitals of the same atom to form new orbitals of the same energy and shape
• Identifying hybridization in organic compounds:

  • If a C-atom forms only sigma bond, it is sp3 hybridized
  • If a C-atom forms one pi bond, it is sp2 hybridized
  • If a C-atom forms two pi bonds, it is sp hybridized
• Carbon compounds can be represented using Lewis electron dot structures, dash-line structures, condensed structures, and bond line structures
• Electronegativity is the capacity of an element to attract shared electrons towards itself
• Ethylethanoate (Ethyl acetate) - O O CH3(CH2)2COOH OH
• Propanitrile (Cyanoethane) - O CH3COOCH2CH3 O
• Three dimensional representation of organic molecules:

  • Solid wedge indicates a bond towards the observer
  • Dashed wedge represents a bond away from the observer
  • Bonds in the plane are represented by normal lines
• Orbital:

  • It is the three-dimensional region in space where the probability of finding an electron is maximum
  • Orbital shapes: Spherical, Dumbbell, Double Dumbbell
• Valency:

  • It is the combining capacity of an atom with other atoms
  • Indicates the number of covalent bonds formed by that atom
  • Valency values for elements: H-1, X-1, O-2, N-3, C-4
• Bonded pair electrons:

  • Electrons involved in bonding are called bonded pair of electrons
• Lone pair electrons:

  • Electrons not involved in bonding are called lone pair of electrons
• Covalent bond:

  • Formed by mutual sharing of electrons between two atoms
  • Single bond: 1 pair of shared electrons
  • Double bond: 2 pairs of shared electrons
  • Triple bond: 3 pairs of shared electrons
• Sigma bond (σ bond):

  • Formed by axial overlap of atomic orbitals
  • Types of σ bonds: (s-s), (s-p), (p-p)
• Pi bond (π bond):

  • Formed by sideways/lateral overlap of p- atomic orbitals
  • Pi bond is perpendicular to the σ-bond
• Classification of organic compounds:

  • Open chain compounds (Acyclic) and Closed chain compounds (Cyclic)
• Open chain compounds (Acyclic):

  • Aliphatic compounds with open chain of carbon atoms
  • Unbranched chain compounds and Branched chain compounds
• Saturated compounds:

  • Aliphatic compounds with only carbon-carbon single bonds (C-C)
  • Example: Alkanes
• Unsaturated compounds:

  • Aliphatic compounds with carbon-carbon multiple bonds (C=C, C≡C)
  • Example: Alkenes and Alkynes
• Aliphatic compounds containing carbon-carbon multiple bonds are Alkenes and Alkynes
• Alkenes are unsaturated aliphatic hydrocarbons with a carbon-carbon double bond (C=C) and have the general formula CnH2n
• Examples of Alkenes:

  • Ethene
  • Propene
  • But-2-ene
• Alkynes are unsaturated aliphatic hydrocarbons with a carbon-carbon triple bond (C≡C) and have the general formula CnH(2n-2)
• Examples of Alkynes:

  • Ethyne
  • Propyne
  • Butyne