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Syllabus of Unit 5 :-

Reactions of synthetic importance
  1. Metal hydride reduction (NaBH4 and LiAlH4)
  2. Clemmensen reduction, Birch reduction, Wolff Kishner reduction.
  3. Oppenauer-oxidation and Dakin reaction.
  4. Beckmann's rearrangement and Schmidt rearrangement.
  5. Claisen-Schmidt condensation

1. Metal hydride reduction

Aldehydes and ketones are converted to primary and secondary alcohols by metallic hydrides like lithium aluminum hydride (LiAlH4) and sodium borohydride (NaBH4). Such a reaction is termed metal hydride reduction reaction. The hydride ion (H–) acts as a nucleophile during this case. By hydride transfer, these metallic hydrides also are accustomed reduce acid halides, carboxylic acids, esters, amides, and other compounds.

Typically, these metallic hydrides don't reduce carbon-carbon double or triple bonds. However, LiAlH4 reduces carbon-carbon multiple bonds in conjugation with an aromatic system on one side of a chemical group on the opposite side.

2. Clemmensen Reduction

The Clemmensen Reduction allows the deoxygenation of aldehydes or ketones, to provide the corresponding hydrocarbon. The substrate must be stable to strong acid. The Clemmensen Reduction is complementary to the Wolff-Kishner Reduction, which is run under strongly basic conditions. Acid-labile molecules should be reduced by the Wolff-Kishner protocol.

3. Beckmann Rearrangement

The Beckmann rearrangement may be a reaction employed in many sectors to convert oximes to amides. The reaction has greatly been improved since its discovery within the sense of safety and viability. This work focuses on the history of the Beckmann rearrangement and enhancements applied to current syntheses of mass-produced, widely available compounds that previously utilized expensive, toxic, and difficult to synthesize or hard to get reagents.

4. Claisen Schmidt Condensation

In chemistry, the Claisen–Schmidt condensation is that the reaction between an aldehyde or ketone having an α-hydrogen with an aromatic carbonyl compound lacking an α-hydrogen. This reaction is known as after two of its pioneering investigators Rainer Ludwig Claisen and J. G. Schmidt, who independently published on this topic in 1880 and 1881. An example is that the synthesis of dibenzylideneacetone