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Chapter 5: Problem 197

Which of the following statements relating to the derivatives of carboxylic acids are correct? (a) An amide \(\mathrm{R}-\mathrm{C}\), answers all the tests for a primary amine. (b) Esters undergo hydrolysis more readily than acid amides.. (c) Carboxylic acid can be converted to an ester by reacting with alcohol in the presence of a base (d) Benzoic acid can be converted to methyl benzoate by using diazomethane.

Short Answer

Expert verified
a. An amide shows similar properties and reactivity as a primary amine. b. An ester is more prone to undergo hydrolysis than an amide. c. Carboxylic acids can be converted to esters in the presence of bases. d. Benzoic acid can be converted to methyl benzoate using diazomethane. Answer: b, d

Step by step solution

01

Statement (a)

An amide \(\mathrm{R}-\mathrm{C}\) refers to a structure where \(\mathrm{R}\) is the organic group and \(\mathrm{C}\) is the carbonyl group. An amide has a general structure \(\mathrm{RCONR_2}\), where \(\mathrm{R_2}\) can be either hydrogen or another organic group. A primary amine, which has the general structure \(\mathrm{RNH_2}\), can show different properties and reactivity compared to an amide. Since amides have a carbonyl group, they are less basic and less nucleophilic than primary amines. Therefore, the statement (a) is incorrect.
02

Statement (b)

Esters have the general structure \(\mathrm{RCOOR'}\), while acid amides (also known as amides) have the general structure \(\mathrm{RCONR_2}\). Due to the presence of the electron-donating oxygen atom in esters, they are more reactive to nucleophiles than amides, and thus, undergo hydrolysis more readily. This occurs because the carbonyl group of an ester is more electrophilic than that of an amide, causing it to be more prone to nucleophilic attack. Therefore, statement (b) is correct.
03

Statement (c)

Carboxylic acids have the general structure \(\mathrm{RCOOH}\), and they can be converted into esters \(\mathrm{RCOOR'}\) by reacting with alcohols in the presence of an acid catalyst, not a base. The reaction requires protonation of the carbonyl oxygen atom in the carboxylic acid moiety, which cannot occur in the presence of a base. Instead, in the presence of a base, the carboxylate ion is formed due to deprotonation of the carboxylic acid, and esterification does not occur. Thus, statement (c) is incorrect.
04

Statement (d)

Benzoic acid is a carboxylic acid having the structure \(\mathrm{C_6H_5COOH}\). Methyl benzoate has the structure \(\mathrm{C_6H_5COOCH_3}\). Diazomethane (\(\mathrm{CH_2N_2}\)) is a highly reactive compound that can act as a methylation agent. It can be used to convert benzoic acid into methyl benzoate by reacting with the carboxylic acid group. The mechanism involves the nucleophilic attack of diazomethane on the carbonyl carbon of benzoic acid, followed by the elimination of nitrogen gas, ultimately forming methyl benzoate. Therefore, statement (d) is correct. In conclusion, statements (b) and (d) are correct, while statements (a) and (c) are incorrect.

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Most popular questions from this chapter

Which of the following pairs will give effervescence with aqueous sodium hydrogen carbonate solution? (a) \(\mathrm{CH}_{3} \mathrm{COCl}\) and \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CO}\) (b) \(\mathrm{CH}_{3} \mathrm{CONH}_{2}\) and \(\left(\mathrm{CH}_{3} \mathrm{CO}\right)_{2} \mathrm{O}\) (c) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH}\) and \(\mathrm{CH}_{3} \mathrm{COOCH}_{3}\) (d) \(\mathrm{CH}_{3} \mathrm{COCl}\) and \(\left(\mathrm{CH}_{3} \mathrm{CO}\right)_{2} \mathrm{O}\)

\(\mathrm{C}_{6} \mathrm{H}_{5}-\mathrm{CH}_{2}-\mathrm{CN} \stackrel{\mathrm{R}}{\longrightarrow} \mathrm{C}_{6} \mathrm{H}_{5}-\mathrm{CH}_{2}-\mathrm{CHO}\) The reagent R used for the above conversion is (a) \(\mathrm{NaBH}_{4}\) (b) \(\mathrm{H}_{2} / \mathrm{Pd}-\mathrm{BaSO}_{4}\) (c) \(\mathrm{Na} / \mathrm{liq} \mathrm{NH}_{3}\) (d) \(\mathrm{SnCl}_{2} / \mathrm{HCl}\)

The IUPAC name of product (B) is (a) Heptane-2, 6 -dione (b) 6 -oxoheptanoic acid (c) 5 -oxohexanal (d) 6 -oxoheptanal

The reagent that can be used for the conversion of \(\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCHO}\) to \(\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCOOH}\) is (a) Alkaline \(\mathrm{KMnO}_{4}\) (b) \(\mathrm{Zn}(\mathrm{Hg}) / \mathrm{HCl}\) (c) \(\mathrm{PCC} / \mathrm{CH}_{2} \mathrm{Cl}_{2}\) (d) Tollens' reagent

p-cresol \(\stackrel{\mathrm{CHCl}_{3} \mathrm{NaOH}}{\longrightarrow} \mathrm{A} \stackrel{\mathrm{HCN}}{\longrightarrow} \mathrm{B} \stackrel{\mathrm{H}, \mathrm{O}^{+}}{\longrightarrow} \mathrm{C}\) Which of the following statements is not true about the product (C) in the above sequence of reactions? (a) It gives violet colour with neutral ferric chloride solution. (b) It is optically active. (c) There are six \(\mathrm{sp}^{2}\) hybridised carbon atoms in one molecule of it. (d) It liberates \(\mathrm{CO}_{2}\) when treated with \(\mathrm{NaHCO}_{3}\) solution.
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