Neucleophilic Acyl substitution of unsymmetrical Acid Anhydrides

In summary, the reaction between an acid anhydride and an alcohol results in the formation of an ester and carboxylic acid. In the case of a symmetrical acid anhydride with only one alkyl group (R), the ester formed will have R as the alkyl group. If the acid anhydride is unsymmetrical (R1COO-COR2), the ester formed will have the more reactive carbonyl carbon (R1) as the alkyl group.
  • #1
sodaboy7
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Consider the following reaction:

RCOO-COR + R'-OH → RCOO-R' + RCOOH (where -R is an alkyl group)

In above reaction the acid anhydride and an alcohol forms ester and carboxylic acid.
The acid anhydride used in this case is a symmetrical on that is containing only one alkyl group (R). My question is that if it is unsymmetrical (say R1COO-COR2), which alkyl group will form ester and which alkyl group will form carboxylic acid. That is will ester formed will have R1 or R2 ?
 
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  • #2
sodaboy7 said:
Consider the following reaction:

RCOO-COR + R'-OH → RCOO-R' + RCOOH (where -R is an alkyl group)

In above reaction the acid anhydride and an alcohol forms ester and carboxylic acid.
The acid anhydride used in this case is a symmetrical on that is containing only one alkyl group (R). My question is that if it is unsymmetrical (say R1COO-COR2), which alkyl group will form ester and which alkyl group will form carboxylic acid. That is will ester formed will have R1 or R2 ?
Alcohol attack to more reactive carbonyl carbon which produced ester, reactivity of carbonyl carbon towards electron withdrawing group attached or less steric alkyl group. If R= CH3 and R'= CH3CH2 , ester formation preferred R carbonyl...
 

1. What is a nucleophilic acyl substitution reaction?

A nucleophilic acyl substitution reaction is a type of organic reaction where a nucleophile (an electron-rich species) replaces a leaving group in an acyl group (a carbonyl group attached to an alkyl or aryl group). It is a common mechanism for the synthesis of carboxylic acid derivatives, such as esters, amides, and carboxylic acids.

2. What is an unsymmetrical acid anhydride?

An unsymmetrical acid anhydride is a type of compound that contains two different acyl groups attached to the same oxygen atom. This means that the two acyl groups have different reactivities, making the reaction potentially more complex than with a symmetrical acid anhydride.

3. What are the key steps in a nucleophilic acyl substitution of unsymmetrical acid anhydrides?

The key steps in this reaction are: (1) nucleophilic attack on the carbonyl carbon, (2) formation of a tetrahedral intermediate, (3) loss of the leaving group, and (4) proton transfer to form the final product. These steps may occur in a different order depending on the specific reaction conditions and reactants.

4. What factors affect the rate of nucleophilic acyl substitution of unsymmetrical acid anhydrides?

The rate of this reaction can be influenced by several factors, including the nature of the nucleophile, the electronic and steric effects of the acyl groups, the solvent, and the reaction temperature. The more stable the intermediate formed, the faster the reaction will proceed.

5. What are some common applications of nucleophilic acyl substitution of unsymmetrical acid anhydrides?

This reaction is commonly used in the synthesis of various carboxylic acid derivatives, such as esters, amides, and carboxylic acids. It is also utilized in the production of pharmaceuticals, fragrances, and other organic compounds. Additionally, this reaction can be used to introduce functional groups onto a molecule or to create new carbon-carbon bonds.

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