Haloalkanes Nucleophilic Substitution Reactions

Haloalkanes

Nucleophilic Substitution

• Haloalkanes undergo nucleophilic substitution reactions, where a nucleophile (a species with an electron pair) replaces the halogen atom.
• Types of nucleophilic substitution reactions:
  1. S_N_1 (Unimolecular Nucleophilic Substitution):
     • Rate-determining step: Formation of a carbocation intermediate.
     • Fast step: Nucleophile attacks the carbocation.
     • Stereospecific: Racemic mixture formed.
  2. S_N_2 (Bimolecular Nucleophilic Substitution):
     • Concerted mechanism: Nucleophile attacks the carbon atom simultaneously with the departure of the leaving group.
     • Stereospecific: Inversion of stereochemistry.

Chemical Reactions

• Haloalkanes can undergo various chemical reactions, including:
  • Hydrolysis: Reaction with water to form an alcohol.
  • Alkaline hydrolysis: Reaction with hydroxide ions to form an alcohol.
  • Grignard reaction: Reaction with Grignard reagents to form a carbon-carbon bond.

Haloarenes

Electrophilic Aromatic Substitution

• Haloarenes undergo electrophilic aromatic substitution reactions, where an electrophile (a species that accepts an electron pair) replaces the halogen atom.
• Types of electrophilic aromatic substitution reactions:
  • Halogenation: Replacement of a halogen atom with another halogen atom.
  • Nitration: Replacement of a halogen atom with a nitro group (-NO2).
  • Sulfonation: Replacement of a halogen atom with a sulfo group (-SO3H).
• Mechanism:
  1. Formation of an electrophile (e.g., bromine or chlorine molecule).
  2. Electrophile attacks the aromatic ring, forming a carbocation intermediate.
  3. Loss of a proton to form the product.

Chemical Reactions

• Haloarenes can undergo various chemical reactions, including:
  • Nucleophilic aromatic substitution: Reaction with a nucleophile to replace the halogen atom.
  • Reductive dehalogenation: Reaction with a reducing agent to remove the halogen atom.

Haloalkanes

Nucleophilic Substitution

• Haloalkanes undergo nucleophilic substitution reactions, where a nucleophile replaces the halogen atom.
• There are two types of nucleophilic substitution reactions:

S_N_1 (Unimolecular Nucleophilic Substitution)

• Rate-determining step is the formation of a carbocation intermediate.
• Fast step is the nucleophile attacking the carbocation.
• Reaction is stereospecific, resulting in a racemic mixture.

S_N_2 (Bimolecular Nucleophilic Substitution)

• Reaction occurs through a concerted mechanism, where the nucleophile attacks the carbon atom simultaneously with the departure of the leaving group.
• Reaction is stereospecific, resulting in an inversion of stereochemistry.

Chemical Reactions

• Haloalkanes can undergo various chemical reactions, including:
• Hydrolysis: reaction with water to form an alcohol.
• Alkaline hydrolysis: reaction with hydroxide ions to form an alcohol.
• Grignard reaction: reaction with Grignard reagents to form a carbon-carbon bond.

Haloarenes

Electrophilic Aromatic Substitution

• Haloarenes undergo electrophilic aromatic substitution reactions, where an electrophile replaces the halogen atom.
• There are three types of electrophilic aromatic substitution reactions:
• Halogenation: replacement of a halogen atom with another halogen atom.
• Nitration: replacement of a halogen atom with a nitro group (-NO2).
• Sulfonation: replacement of a halogen atom with a sulfo group (-SO3H).
• The mechanism involves:
• Formation of an electrophile (e.g., bromine or chlorine molecule).
• Electrophile attacking the aromatic ring, forming a carbocation intermediate.
• Loss of a proton to form the product.

Chemical Reactions

• Haloarenes can undergo various chemical reactions, including:
• Nucleophilic aromatic substitution: reaction with a nucleophile to replace the halogen atom.
• Reductive dehalogenation: reaction with a reducing agent to remove the halogen atom.