haloalkane and haloarene notes 12th chemistry

Haloalkanes:

• Haloalkanes are organic compounds that contain at least one halogen atom (F, Cl, Br, or I) attached to a carbon atom in a hydrocarbon chain.
• They are also known as alkyl halides.
• They are classified as primary, secondary, or tertiary based on the number of carbon atoms directly attached to the carbon with the halogen.
• Haloalkanes are generally polar due to the electronegativity of the halogen atom, which makes them good solvents for polar molecules.
• They can undergo nucleophilic substitution reactions, in which a nucleophile replaces the halogen atom.
• The most common nucleophiles are OH-, CN-, and NH3.

Haloarenes:

• Haloarenes are organic compounds that contain a halogen atom (F, Cl, Br, or I) attached to a carbon atom in an aromatic ring.
• They are also known as aryl halides.
• They are generally less reactive than haloalkanes due to the stability of the aromatic ring.
• They can undergo nucleophilic aromatic substitution reactions, in which a nucleophile replaces a halogen atom on the aromatic ring.
• The most common nucleophiles in these reactions are NH3 and OH-.

Some common reactions of haloalkanes and haloarenes:

• Nucleophilic substitution reactions: In these reactions, a nucleophile replaces the halogen atom. These reactions are commonly used to prepare alcohols, amines, and other organic compounds.
• Elimination reactions: In these reactions, a halogen atom and a hydrogen atom are removed from adjacent carbon atoms, forming a double bond. These reactions are commonly used to prepare alkenes and alkynes.
• Nucleophilic aromatic substitution reactions: In these reactions, a nucleophile replaces a halogen atom on an aromatic ring. These reactions are used to prepare a variety of organic compounds, including drugs and dyes.

1. Nucleophilic substitution reactions: Haloalkanes can undergo nucleophilic substitution reactions with a variety of nucleophiles, such as water, ammonia, and alkoxides. These reactions are typically classified into two types: SN1 and SN2. In an SN1 reaction, the halogen atom is first displaced by a nucleophile, forming a carbocation intermediate. In an SN2 reaction, the nucleophile attacks the carbon atom bearing the halogen atom at the same time that the leaving group (halogen) departs.

2. Elimination reactions: Haloalkanes can undergo elimination reactions, in which a halogen atom and a hydrogen atom are removed from adjacent carbon atoms, forming a double bond. These reactions are typically classified into two types: E1 and E2. In an E1 reaction, the halogen atom leaves first, forming a carbocation intermediate, which then loses a proton to form the double bond. In an E2 reaction, the halogen atom leaves at the same time that the hydrogen atom is removed by a base, forming the double bond.

3. Formation of Grignard reagents: Haloalkanes can react with magnesium metal to form Grignard reagents, which are highly reactive organometallic compounds. These reagents can be used in a variety of organic synthesis reactions.

Some important reactions of haloarenes include:

1. Nucleophilic aromatic substitution reactions: Haloarenes can undergo nucleophilic aromatic substitution reactions, in which a nucleophile replaces a halogen atom on the aromatic ring. These reactions are typically classified into two types: SNAr and Benzyne mechanisms. In an SNAr reaction, the nucleophile attacks the aromatic ring, displacing the halogen atom. In a Benzyne mechanism, the halogen atom is first removed to form a highly reactive benzyne intermediate, which then reacts with a nucleophile.

2. Formation of organometallic compounds: Haloarenes can react with metals, such as magnesium or lithium, to form organometallic compounds. These compounds can be used in a variety of organic synthesis reactions.

3. Coupling reactions: Haloarenes can undergo coupling reactions, in which two aromatic rings are joined together through a carbon-carbon bond. The most common type of coupling reaction is the Suzuki-Miyaura coupling, which uses a palladium catalyst to form the carbon-carbon bond.

1. Reaction with metals: Haloalkanes can react with metals like sodium, lithium, or magnesium to form alkyl metal compounds. These reactions are important for the synthesis of various organic compounds.

Reactions of Haloarenes:

1. Nucleophilic aromatic substitution reactions: In these reactions, a nucleophile replaces a halogen atom on an aromatic ring. The reaction mechanism involves the attack of the nucleophile on the electrophilic carbon atom of the aromatic ring, followed by the expulsion of the halide ion.

2. Sandmeyer reaction: This reaction involves the conversion of a diazonium salt of an aromatic amine to a haloarene by replacing the -N2+ group with a halogen. The reaction can be used to introduce a variety of halogens onto an aromatic ring.

3. Gattermann reaction: This reaction involves the substitution of a hydrogen atom on an aromatic ring with a halogen atom in the presence of a Lewis acid catalyst like AlCl3. The reaction can be used to introduce a variety of halogens onto an aromatic ring.