Lead Tetraacetate (LTA)
Very Important for B.Sc., M.Sc., CSIR, GATE, JAM, SLET, and Other Entrance Exams. Preparation
Lead Tetraacetate may be prepared by gradually adding red lead with stirring to a mixture of acetic acid and acetic anhydride at 55° to 88°C temperature.
Uses
1. As Oxidizing Agent
With Monohydric Alcohols
Primary and Secondary alcohols converted into Aldehydes and Ketones respectively.
With Dihydric Alcohols
Alcohols having δ-hydrogen may be cyclized.
Lead Tetraacetate also oxidize compounds having nitrogen and oxygen -nitrogen on adjacent carbon atoms.
Lead Tetraacetate also oxidize hydroxyquinone to quinone.
Oxidation of α-hydroxy acids and α-keto acids to ketones and acids respectively.
-COOH with LTA generally gives decarboxylated product but when double bond present nearby, lactone is formed and when β-H is present then alkene is formed.
Succinic acid derivatives undergoes bisdecarboxylation with Lead Tetraacetate and gives alkenes.
Malonic acid derivatives undergoes bisdecarboxylation with Lead Tetraacetate and gives Ketones.
Oxidation of Aromatic primary amines with lead tetraacetate gives Azo compounds.
2. As Methylating and Acetoxylating Agent
As Methylating Agent
Direct methylation takes place when boiled with LTA and glacial AcOH.
Benzene gives Taulene and TNB gives TNT
As Acetoxylation Agent
Molecules having enolizable keto group undergoes acetoxylation with lead tetraacetate.
In cyclo alkenes, both the double bond and allylic positions are actoxylated.
Summary
1. It is a strong Oxidizing agent
2. It ia a source of Acetyloxy and Methyl group
3. It convert Alkenes to γ Lactones
4. It oxidize alcohols carrying a δ proton to cyclic ethers
5. It make oxidative cleavage of certain allyl alcohols in conjugation with ozone
6. It converts 1,2-diol to corresponding aldehydes or ketones
7. It also convert Acetophenone to Pheylacetic acid
8. Decarboxylation of Carboxylic acids to Alkyl halide with LiCl or other Li-salts (Kochi Reaction)
Important Reactions with Lead Tetraacetate1. It is a strong Oxidizing agent
2. It ia a source of Acetyloxy and Methyl group
3. It convert Alkenes to γ Lactones
4. It oxidize alcohols carrying a δ proton to cyclic ethers
5. It make oxidative cleavage of certain allyl alcohols in conjugation with ozone
6. It converts 1,2-diol to corresponding aldehydes or ketones
7. It also convert Acetophenone to Pheylacetic acid
8. Decarboxylation of Carboxylic acids to Alkyl halide with LiCl or other Li-salts (Kochi Reaction)
