In which of the following reactions,we will get new C-C bond?
Cannizzaro reaction and Aldol condensation reaction
Cannizzaro reaction and Sandmeyer's reaction
Friedel-Crafts reaction and Gattermann-Koch reaction
Cannizzaro reaction and Reimer-Tiemann reaction
Sandmeyer's reaction and Aldol condensation reaction
The Correct Option is C
Solution and Explanation
Cannizzaro Reaction: This reaction involves the disproportionation of aldehydes lacking alpha-hydrogens in the presence of a strong base. One aldehyde is reduced to an alcohol, and the other is oxidized to a carboxylic acid. No new C-C bond is formed.
Aldol Condensation: This reaction involves the nucleophilic addition of an enolate ion to a carbonyl group (aldehyde or ketone), forming a beta-hydroxyaldehyde or beta-hydroxyketone (aldol). This is followed by dehydration to form an alpha, beta-unsaturated carbonyl compound. A new C-C bond is formed between the alpha carbon of one molecule and the carbonyl carbon of the other.
Sandmeyer's Reaction: This is a method for synthesizing aryl halides from aryl diazonium salts, which are obtained from aromatic amines. The diazonium salt is replaced by a halide (Cl, Br) or other group (CN) in the presence of a copper(I) salt. No new C-C bond is formed directly in this step.
Friedel-Crafts Reaction: This reaction involves the alkylation or acylation of aromatic compounds. An alkyl or acyl group is attached to the aromatic ring. A new C-C bond is formed between the aromatic ring and the alkyl/acyl group.
Gattermann-Koch Reaction: This is a variation of the Friedel-Crafts acylation, used to form aromatic aldehydes using CO and HCl in the presence of a Lewis acid catalyst (e.g., AlCl3). A new C-C bond is formed (although it is converted to a C=O bond in the aldehyde).
Reimer-Tiemann Reaction: This reaction is used to form ortho-hydroxybenzaldehydes from phenols, using chloroform, base, and heat. A new C-C bond is formed in adding the -CHO group to the ring.
Thus, the correct option is (C): Friedel-Crafts reaction and Gattermann-Koch reaction
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Concepts Used:
Chemical Bonding and Molecular Structure
Such a group of atoms is called a molecule. Obviously, there must be some force that holds these constituent atoms together in the molecules. The attractive force which holds various constituents (atoms, ions, etc.) together in different chemical species is called a chemical bond.
Types of Chemical Bonds:
There are 4 types of chemical bonds which are formed by atoms or molecules to yield compounds.
- Ionic Bonds - Ionic bonding is a type of chemical bonding which involves a transfer of electrons from one atom or molecule to another.
- Covalent Bonds - Compounds that contain carbon commonly exhibit this type of chemical bonding.
- Hydrogen Bonds - It is a type of polar covalent bonding between oxygen and hydrogen wherein the hydrogen develops a partial positive charge
- Polar Bonds - In Polar Covalent chemical bonding, electrons are shared unequally since the more electronegative atom pulls the electron pair closer to itself and away from the less electronegative atom.
Factors Affecting Bond Enthalpy in Chemical Bonding:
- Size of the Atom
- Multiplicity of Bonds
- Number of Lone Pair of Electrons Present
- Bond Angle