REACTION MECHANISM

• Reaction Mechanism

  • An overall description of how a reaction occurs.
• Reaction Mechanism

  Detailed:

  • Sequence of stepsDetails of electron movement
  • Bond-breaking and bond making
• TYPES OF BOND CLEAVAGE

  1. HOMOLYTIC CLEAVAGE
  2. HETEROCYCLIC CLEAVAGE
• HOMOLYTIC CLEAVAGE

  • Breaking of a bond in an electronically symmetrical way so that one electron remains with each product fragment.
• HETEROCYCLIC CLEAVAGE

  • Breaking of a bond in an electronically unsymmetrical way so both bonding electrons remain with one product fragment, leaving the other with a vacant orbital.
• TYPES OF REAGENT - NUCLEOPHILE, ELECTROPHILE
• NUCLEOPHILE

  • has a negatively polarized, electron-rich atom
• NUCLEOPHILE

  • can form a bond by donating a pair of electrons to a positively polarized, electron-poor atom.can be either neutral or negatively charged;
• ELECTROPHILE

  has a positively polarized, electron-poor atom
• ELECTROPHILE

  • can form a bond by accepting a pair of electrons from a nucleophile.
  • can be either neutral or positively charged.
• TYPES OF INTERMEDIATE PRODUCTS

  • Carbocation
  • Carbanion
  • Carbon radical
• Carbocation

  • substance that contains a Trivalent, Positively charged carbon having six electrons in outer shell
• Carbanion - substance that contains a trivalent, negatively charge carbon atom
• Carbon Radical - A carbon with an odd number of electrons in its outer shell
• Stereochemistry

  Chemistry of Space; 3D Chemistry
• Stereochemistry

  deals with the spatial arrangements of atoms and groups in a molecule.
• stereoisomers

  • chemical compounds with the same chemical formula but a different spatial arrangement in three dimensions
• TYPES OF ISOMERS

  • CONSTITUTIONAL ISOMER/STRUCTURAL ISOMER
  • STEREOISOMERS
• CONSTITUTIONAL ISOMER/STRUCTURAL ISOMER

  isomer with different order of arrangement of atoms or bonds
• types of CONSTITUTIONAL ISOMER/STRUCTURAL ISOMER

  • Chain Isomer
  • Position Isomer
  • Functional Isomer (includes Tautomers)
• Chain Isomer

  • Isomer with a different arrangement of molecule’s carbon skeleton
  • Eg. Straight-chain & Branched-chain
• Position Isomer

  Isomer with different positions of the substituent of the same functional group
• Functional Isomer

  Isomer with a different functional group
• TAUTOMERS

  Special type of functional Isomer which occurs between Keto form (Aldehyde or Ketone) to Enol form (ene + ol)
• Keto to Enol

  • Base-Catalyzed Tautomerization
• Tautomerization

  shift of the hydroxyl to carbon 2 of the alkene, and vice versa
• Enol to Keto

  • Acid-Catalyzed
• Tautomers

  are isomers that differ in the position of protons and electrons, usually involving the relocation of a hydrogen atom and a double bond.
• Keto-enol tautomerism

  involves the interconversion between a keto form (C=O) and an enol form (C=C-OH).
• Base-catalyzed tautomerization

  involves the abstraction of a proton from the alpha-carbon, forming an enolate ion, which is then protonated to form the enol.
• Acid-catalyzed tautomerization

  involves protonation of the carbonyl oxygen, followed by deprotonation of the alpha-carbon to form the enol.
• STEREOISOMERS

  • isomer with same connections between atoms but different three-dimensional arrangements
• Conformational Isomer

  1. Acyclic Conformers
  2. Staggered Conformation
  3. Eclipsed Conformation
  4. Gauche Conformation
  5. Anti-Conformation
• Acyclic Conformers

  exist on open-chain compounds
• Staggered Conformation

  stable conformation of ethane
• Eclipsed Conformation

  • overlapping
• Gauche Conformation

  • 60 degrees rotation
• Anti-Conformation

  stable conformation of butane (180 degrees rotation)
• Cyclic Conformers

  exist in ring structure compound
• Chair conformation

  most stable conformation of cyclohexanes