Answer :
a. Sabatier: Hydrogenate alkenes with nickel.
b. Decarboxylation: Remove COOH from carboxylic acids using soda lime.
c. Wurtz: Coupling of alkyl halides with sodium.
d. Grignard Hydrolysis: Convert RMgX to alkanes with water.
a. Sabatier and Senderens Reactions: The Sabatier and Senderens reactions involve the hydrogenation of alkenes over a nickel catalyst. In this reaction, alkenes react with hydrogen gas (H₂) in the presence of a nickel catalyst at high temperatures (around 150-200°C) to produce alkanes.
The process is effective for converting unsaturated hydrocarbons to saturated ones.
b. Decarboxylation Reaction: Decarboxylation involves the removal of a carboxyl group (COOH) from a carboxylic acid, typically using soda lime (a mixture of calcium oxide and sodium hydroxide).
For example, decarboxylation of sodium acetate with soda lime yields ethane (CH₃-CH₃) and sodium carbonate. This method is useful for synthesizing smaller alkanes from carboxylic acids.
c. Wurtz Reaction: The Wurtz reaction is a coupling reaction where two alkyl halides react with sodium metal in dry ether to form a higher alkane. For example, if ethyl bromide is used, the reaction with sodium produces butane (CH₃-CH₂-CH₂-CH₃). This reaction is useful for synthesizing symmetrical alkanes.
d. Hydrolysis of Grignard Reagents: Grignard reagents (RMgX) react with water (or dilute acid) to form alkanes. For instance, if a Grignard reagent like methylmagnesium bromide (CH₃MgBr) is hydrolyzed, it produces methane (CH₄).
The Grignard reagent reacts with water to yield the corresponding alkane and magnesium hydroxide or magnesium salt of the acid.
Note the complete question is:
Explain the following synthesis methods for alkanes:
a. Sabatier and Senderens reactions [5]
b. Decarboxylation reaction [5]
c. Wurtz reaction [5]
d. Hydrolysis of Grignard reagents [5]
