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The most suitable reagent for the given conversion is:

Option: 1

B_{2}H_{6}
 


Option: 2

LiAIH_{4}


Option: 3

NaBH_{4}

 


Option: 4

H_{2}/Pd


Answers (1)

best_answer

As we have learnt,

 

Chemical Properties of Carboxylic Acids -

Formation of Anhydride
Carboxylic acid on heating with H2SO4 or P2O5 gives corresponding anhydride. The reaction occurs as follows:

Reaction with Ammonia
On heating with NH3, carboxylic acid gives ammonium salt which on further heating at high temperature gives amides. The reaction occurs as follows:

Reduction
Carboxylic acids are reduced to 1o alcohol by LiALH4 or better with B2H6. B2H6 does not easily reduce esters, nitro, and halo groups, and NaBH4 does not reduce (-COOH) group. 
 

Decarboxylation
When sodium salts of carboxylic acids are heated with soda lime (NaOH and CaO in 3:1 ratio), they form hydrocarbons by losing CO2. This is known as decarboxylation. 
 

Kolbe's electrolysis
The electrolysis of aqueous solution of sodium or potassium salts of carboxylic acid makes the carboxylic acid to undergo decarboxylation to form alkane. The reaction occurs as follows:

Halogenation
The method of preparing α-chloro or α-bromo acid is by Hell-Volhard-Zelinsky reaction, which is carried out by treating the acid with Cl2 or Br2 in the presence of a small amount of red phosphorous. The reaction occurs as follows:

Ring substitution
Aromatic carboxylic acid undergoes substitution electrophilic reactions in which the (-COOH) group acts as a deactivating and meta-directing group. It does not undergo Friedel-Crafts reaction because the (-COOH) group is deactivating and the catalyst AlCl3 gets bonded to the (COOH) group. The reactions occur as follows:

B2H6 is very selective and usually used to reduce acid to alcohol.

Therefore, Option(1) is correct.

Posted by

Suraj Bhandari

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