Chapter 20, Problem 20.36P

Interpretation Introduction

(a)

Interpretation:

The product of the reaction between actic anhydride and the given reactant is to be predicted. A complete, detailed mechanism is to be drawn if the reaction occurs.

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). 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 20.36P

The product of the given reaction is

The complete mechanism of the reaction is

Explanation of Solution

The given reactant is NaOH followed by ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$. The product of the reaction will be a carboxylic acid, more stable than the reactant. Therefore, the reaction will occur. The hydroxide ion from NaOH will replace the chlorine in the acid chloride, producing the corresponding carboxylic acid.

Thus, the product of the reaction will be

The reaction will start with the nucleophilic addition of hydroxide ion from NaOH, producing a tetrahedral intermediate.

In the second step, one lone pair from negatively charged oxygen will move back to the carbon to reform the carbonyl group and eliminate an acetate ion. This step will produce one acetate ion and one acetic acid molecule, but under the strongly basic conditions, the acid will be irreversibly deprotonated to produce two carboxylate anions.

The addition of the acid (${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$) at the end of this reaction will convert the carboxylate back to the acid.

Thus, the complete mechanism can be drawn as

Conclusion

The product of the reaction and its mechanism were determined based on the relative stability of the produc, and the nucleophilic addition-elimination mechanism.

Interpretation Introduction

(b)

Interpretation:

The product of the reaction between acetic anhydride and the given reactant is to be predicted. A complete, detailed mechanism is to be drawn if the reaction occurs.

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). 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 20.36P

The products of the given reaction are

The complete mechanism of the reaction is

Explanation of Solution

The given reactant is ${\text{CH}}_{\text{3}}\text{NHLi}$ that acts as the nucleophile ${\text{CH}}_{\text{3}}{\text{HN}}^{-}\text{:}$. Nucleophilic addition-elimination of the incoming nucleophile will produce an amide which is more stable than the reactant acid anhydride. Therefore, the nucleophile will add to the carbonyl carbon to produce a tetrahedral intermediate in the first step.

One lone pair on negatively charged oxygen will move back toward the carbon to reform the carbnyl group and eliminate an acetate ion to form the final product.

Thus, the product of the reaction will be

And the complete mechanism can be drawn as

Conclusion

The product of the reaction and its mechanism were dsetermined based on the relative stability of the product and the nucleophilic addition-elimination mechanism.

Interpretation Introduction

(c)

Interpretation:

The product of the reaction between acetic anhydride and the given reactant is to be predicted. A complete, detailed mechanism is to be drawn if the reaction occurs.

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). 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 20.36P

The product of the given reaction is

The complete mechanism of the reaction is

Explanation of Solution

The given reactant is ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{OK}$, containing the nucleophile ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{O}}^{-}$. Nucleophilic addition-elimination will produce an ester, a derivative that is more stable than the reactant acid anhydride.

Therefore, the product of the reaction will be

In the first step, the incoming nucleophile will add to the carbonyl carbon, producing a tetrahedral intermediate.

The lone pair on negativey charged ocygen will move back toward the carbon to reform the carbonyl group and eliminate acetate anion to form the final product, an ester.

Thus, the complete mechanism can be drawn as

Conclusion

The product of the reaction and its mechanism were dsetermined based on the relative stability of the product and the nucleophilic addition-elimination mechanism.

Interpretation Introduction

(d)

Interpretation:

The product of the reaction between aceetic anhydride and the given reactant is to be predicted. A complete, detailed mechanism is to be drawn if the reaction occurs.

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). 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 20.36P

The product of the given reaction is

The complete mechanism of the reaction is

Explanation of Solution

The given reactant is ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}{\text{CO}}_{\text{2}}\text{K}$, containing the nucleophile ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}{\text{COO}}^{-}$. Nucleophilic addition-elimination will produce annother acid anhydride, of comparable stability. Since the reactant and product have comparable stability, the reaction will be reversible.

Therefore, the product of the reaction will be

In the first step, the nucleophile will add to the carbonyl carbon to produce a tetrahedral intermediate.

In the second step, one lone pair of negatively charged oxygen will move back to the carbon to reform the carbonyl group and eliminate acetate anion to form the final product.

Thus, the complete mechanism can be drawn as

Conclusion

The product of the reaction and its mechanism were dsetermined based on the relative stability of the product and the nucleophilic addition-elimination mechanism.

Interpretation Introduction

(e)

Interpretation:

The product of the reaction between acetic anhydride and the given reactant is to be predicted. A complete, detailed mechanism is to be drawn if the reaction occurs.

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). 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 20.36P

There will be no reaction.

Explanation of Solution

The given reactant is NaBr, a source of the nucelophile ${\text{Br}}^{-}$. The potential product of a reaction is an acid bromide, lower in stability than the reactant.

Therefore, the reaction will not occur.

Conclusion

Nucleophilic addition-elimination cannot occur since the possible product is of lower stability than the reactant.

Interpretation Introduction

(f)

Interpretation:

The product of the reaction between acetic anhydride and the given reactant is to be predicted. A complete, detailed mechanism is to be drawn if the reaction occurs.

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). 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 20.36P

The reaction will not occur.

Explanation of Solution

The given reactant is ${\text{CH}}_{\text{3}}{\text{CH}}_2{\text{COCH}}_2{\text{CH}}_{\text{3}}$ an ether. Ethers are weak nucleophiles, and do not add to carbonyl carbon. The potential product is also not a derivative that is more stable than an acid anhydride.

Therefore, there will be no reaction.

Conclusion

Nucleophilic addition-elimination is not possible in this case as the nucleophile is weak and does not add to a carbonyl carbon.

Interpretation Introduction

(g)

Interpretation:

The product of the reaction between acetic anhydride and the given reactant is to be predicted. A complete, detailed mechanism is to be drawn if the reaction occurs.

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). 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 20.36P

The reaction will not occur.

Explanation of Solution

The given reactant is $\text{3-chloropetane}$, a source of electrophilic carbon which cannot participate in a nucleophilic addition-elimination reaction.

Therefore, there will be no reaction.

Conclusion

Nucleophilic addition-elimination is not possible in this case as the given reactant is an electrophile.

Interpretation Introduction

(h)

Interpretation:

The product of the reaction between acetic anhydride and the given reactant is to be predicted. A complete, detailed mechanism is to be drawn if the reaction occurs.

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). 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 20.36P

The reaction will not occur.

Explanation of Solution

The given reactant is hexanal with an electrophilic carbon.

Therefore, there will be no reaction.

Conclusion

Nucleophilic addition-elimination is not possible in this case as the reactant is an electrophile.