Chapter 21, Problem 21.39P

Interpretation Introduction

(a)

Interpretation:

The complete, detailed mechanism and the products are to be drawn for the given reaction.

Concept introduction:

Carboxylic acid derivatives undergo acyl group substitution reactions when treated with appropriate nucleophiles. The reaction occurs via nucleophilic addition-elimination involving a tetrahedral intermediate. It may also involve proton transfer step(s), particularly when the nucleophile being added in the first step is not a strong nucleophile. The reaction occurs if the possible product is more stable than the reactant. If the two are of comparable stability, the reaction will occur reversibly. The order of increasing stability of acid derivatives is

$\text{acid chloride < acid anhydride < ester }\approx \text{ carboxylic acid < amide < carboxylate anion}$

Answer to Problem 21.39P

The complete mechanism is

The product of the reaction is

Explanation of Solution

The given reaction is

Alcohol is a weak nucleophile and adds to one of the carbonyl carbons of acetic anhydride to produce a protonated ether linkage. The carbonyl oxygen becomes negatively charged as a result of the $\text{π}$ bond pair moving to it.

In the next step, the positively charged oxygen is deprotonated by another molecule of the alcohol.

The final step is nucleophilic elimination of acetate anion as a result of the lone pair of the negatively charged oxygen moving to reform the carbonyl group.

Thus, the complete mechanism of the reaction can be drawn as

The product of the reaction is

Conclusion

The product and mechanism of the given reaction are determined on the basis of nucleophilic addition-elimination mechanism.

Interpretation Introduction

(b)

Interpretation:

The complete, detailed mechanism and the products are to be drawn for the given reaction.

Concept introduction:

Carboxylic acid derivatives undergo acyl group substitution reactions when treated with appropriate nucleophiles. The reaction occurs via nucleophilic addition-elimination involving a tetrahedral intermediate. It may also involve proton transfer step(s), particularly when the nucleophile being added in the first step is not a strong nucleophile. The reaction occurs if the possible product is more stable than the reactant. If the two are of comparable stability, the reaction will occur reversibly. The order of increasing stability of acid derivatives is

$\text{acid chloride < acid anhydride < ester }\approx \text{ carboxylic acid < amide < carboxylate anion}$

Answer to Problem 21.39P

The complete mechanism is

The product of the reaction is

Explanation of Solution

The given reaction is

The amine can act as both a nucleophile and a base.

In the first step, it acts as a nucleophile and adds to the carbonyl carbon of the acid chloride to produce a protonated amine linkage. The $\text{π}$ bond pair of the carbonyl group moves to the oxygen, making it negatively charged.

The protonated amine is then deprotonated by a second molecule of the amine.

Finally, one lone pair on the negatively charged oxygen will move back to reform the carbonyl group, eliminating the chloride and forming the product.

Thus, the complete mechanism can be drawn as

And the product of the reaction will be

Conclusion

The product and mechanism of the given reaction are determined on the basis of nucleophilic addition-elimination mechanism.

Interpretation Introduction

(c)

Interpretation:

The complete, detailed mechanism and the products are to be drawn for the given reaction.

Concept introduction:

Carboxylic acid derivatives undergo acyl group substitution reactions when treated with appropriate nucleophiles. The reaction occurs via nucleophilic addition-elimination involving a tetrahedral intermediate. It may also involve proton transfer step(s), particularly when the nucleophile being added in the first step is not a strong nucleophile. The reaction occurs if the possible product is more stable than the reactant. If the two are of comparable stability, the reaction will occur reversibly. The order of increasing stability of acid derivatives is

$\text{acid chloride < acid anhydride < ester }\approx \text{ carboxylic acid < amide < carboxylate anion}$

Answer to Problem 21.39P

The complete mechanism of the reaction is

The product of the reaction is

Explanation of Solution

The given reaction is

The amine will act as a nucleophile and add to the carbonyl carbon of the acid chloride in the first step to form a protonated amine linkage. The $\text{π}$ bond pair of the carbonyl group moves to the oxygen to make it negatively charged.

The protonated amine is deprotonated in the second step by the added base, pyridine.

Finally, one lone pair on the negatively charged oxygen moves back to reform the carbonyl group, eliminating the leaving group chloride and forming the final product.

Thus, the complete mechanism can be drawn as

And the product of the reaction will be

Conclusion

The product and mechanism of the given reaction are determined on the basis of nucleophilic addition-elimination mechanism.

Interpretation Introduction

(d)

Interpretation:

The complete, detailed mechanism and the products are to be drawn for the given reaction.

Concept introduction:

Carboxylic acid derivatives undergo acyl group substitution reactions when treated with appropriate nucleophiles. The reaction occurs via nucleophilic addition-elimination involving a tetrahedral intermediate. It may also involve proton transfer step(s), particularly when the nucleophile being added in the first step is not a strong nucleophile. The reaction occurs if the possible product is more stable than the reactant. If the two are of comparable stability, the reaction will occur reversibly. The order of increasing stability of acid derivatives is

$\text{acid chloride < acid anhydride < ester }\approx \text{ carboxylic acid < amide < carboxylate anion}$

Answer to Problem 21.39P

The complete mechanism of the reaction is

The product of the reaction is

Explanation of Solution

The given reaction is

The alcohol is a weak nucleophile. It will add to one of the carbonyl carbons in the anhydride to produce a protonated intermediate.

In the seconds step, this intermediate will be deprotonated by a second molecule of the alcohol.

Finally, one lone pair from the negatively charged oxygen will move back to reform the carbonyl, eliminating the leaving group benzoate in the process and forming the product.

Thus, the complete mechanism can be drawn as

And the product of the reaction will be

Conclusion

The product and mechanism of the given reaction are determined on the basis of nucleophilic addition-elimination mechanism.