Nucleophilic Substitution

• What are alkyl halides also known as?

  Halogenoalkanes
• What defines alkyl halides in terms of structure?

  Alkyl group bound to a halogen atom
• What elements can the halogen atom (X) in alkyl halides be?

  F, Cl, Br, or I
• What are organic halogen compounds?

  Compounds with halogens combined with carbon
• What is an alkyl group?

  A functional group missing an H
• What is the structure of alkyl halides?

  • Contains sp3 carbon atom
  • Tetrahedral geometry
  • C-X bond formed by overlap of orbitals
• What is the example of a methyl group?

  CH3
• Why are R-F compounds very unreactive?

  They have very strong covalent R-X bonds
• How are organic halogen compounds made?

  Through hydrohalogenation and halogenation
• What are the three types of reactions with alkyl halides?

  1. Nucleophilic Substitution (SN1 & SN2)
  2. Elimination (E2)
  3. Addition reactions (not covered here)
• Why are alkyl halides considered reactive compounds?

  Due to the nature of the C-X bond
• What role do alkyl halides play in reactions?

  They can react with nucleophiles or bases
• What is an elimination reaction in the context of alkyl halides?

  • Uses a base
  • Both X and H are lost
  • Alkene is formed
• What is a nucleophilic substitution reaction?

  • Uses a nucleophile
  • Nucleophile substitutes a halogen
  • Not an addition reaction
• What is the leaving group in a nucleophilic substitution reaction?

  The halogen (X)
• Why do alkyl halides undergo nucleophilic substitution reactions?

  Due to the polar covalent bond
• What is the characteristic of a good nucleophile?

  It is electron-rich
• How does electronegativity affect nucleophilicity?

  • Increases from bottom to top in a group
  • Decreases from left to right in a period
• Which type of ions are better nucleophiles?

  Negative ions
• What happens to nucleophilicity as you move down a group in the periodic table?

  Nucleophilicity increases
• What happens to nucleophilicity as you move left to right in a period?

  Nucleophilicity decreases
• What is the effect of alkyl groups on nucleophilic substitution rates?

  • Methyl: fastest
  • Primary (1°): faster
  • Secondary (2°): slower
  • Tertiary (3°): slowest
• What do the differences in reaction rates suggest about SN reactions?

  There are two different reaction mechanisms
• What are the two mechanisms for nucleophilic substitution reactions?

  1. SN1
  2. SN2
• How are the rates of nucleophilic substitution reactions determined?

  Through experimental kinetic studies
• What does the overall order of the reaction indicate?

  It helps explain alkyl halide reaction processes
• What are the three types of alkyl halides?

  Primary, secondary, tertiary
• What is the leaving group in the SN reaction example?

  Bromide
• What does increasing steric hindrance affect in SN reactions?

  It affects the reaction rate
• What are the two mechanisms for SN reactions with alkyl halides?

  SN1 and SN2
• What does the rate equation for SN reactions indicate?

  It shows the relationship between reactants
• What is the general rate equation for SN reactions with alkyl halides?

  • Rate = k[RX][Nu]
  • k = reaction constant
  • [RX] = concentration of alkyl halide
  • [Nu] = concentration of nucleophile
• What is the order of reaction for SN2 mechanisms?

  Bimolecular, second order
• What is the order of reaction for SN1 mechanisms?

  Unimolecular, first order
• What is the significance of the transition state in SN2 reactions?

  It cannot be isolated and indicates reaction progress
• What happens during the "backside attack" in SN2 reactions?

  Nucleophile approaches opposite to leaving group
• How does the SN2 reaction mechanism differ from SN1?

  SN2 is concerted, while SN1 involves intermediates
• What is the role of hydroxide in the SN2 reaction example?

  It acts as a nucleophile
• What are the characteristics of a good leaving group in SN reactions?

  • Good leaving groups: Cl, Br, I
  • Poor leaving group: F
  • Leaving group ability affects reaction rate
• What is the effect of the nucleophile's charge in SN2 reactions?

  A negatively charged nucleophile is preferred