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Chapter 2: Problem 75

An ester on hydrolysis gave an acid which on Kolbe's electrolysis gave ethane. The ester is (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COO} \mathrm{CH}_{3}\) (b) (c) \(\mathrm{CH}_{3} \mathrm{COO} \mathrm{C}_{2} \mathrm{H}_{5}\) (d) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{COO} \mathrm{C}_{2} \mathrm{H}_{5}\)

Short Answer

Expert verified
Answer: The correct ester that produces ethane after hydrolysis and subsequent Kolbe's electrolysis is \(\mathrm{CH}_{3} \mathrm{COO} \mathrm{C}_{2} \mathrm{H}_{5}\).

Step by step solution

01

Ester Hydrolysis Reaction

The general equation for the hydrolysis of an ester is: \(\mathrm{R}_{1} \mathrm{COOR}_{2} + \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{R}_{1} \mathrm{COOH} + \mathrm{R}_{2} \mathrm{OH}\) Where R1 and R2 are alkyl groups or hydrogen atoms. Hydrolysis produces a carboxylic acid and an alcohol, given ester as input.
02

Kolbe's Electrolysis Reaction

Kolbe's electrolysis involves the electrolysis of a carboxylic acid salt to produce an alkane, carbon dioxide, and water. The general equation is given by: \(2 \mathrm{RCOO}^{-} + 2 \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{R-R} + 2 \mathrm{CO}_{2} + 4 \mathrm{H}^{+}\) The hydrolysis of ester will produce an acid, and Kolbe's electrolysis of that acid will result in ethane formation.
03

Identify the Correct Ester Option

We will now go through each ester option to see if the correct series of reactions yields ethane. 1. Option (a): \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COO} \mathrm{CH}_{3}\) Hydrolysis: \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COO} \mathrm{CH}_{3} + \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COOH} + \mathrm{CH}_{3} \mathrm{OH}\) Kolbe's electrolysis (produces ethene, not ethane): \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COO}^{-} \rightarrow \mathrm{CH}_{2} = \mathrm{CH}_{2} + 2 \mathrm{CO}_{2} + 4 \mathrm{H}^{+}\) So option (a) is not the correct answer. 2. Option (c): \(\mathrm{CH}_{3} \mathrm{COO} \mathrm{C}_{2} \mathrm{H}_{5}\) Hydrolysis: \(\mathrm{CH}_{3} \mathrm{COO} \mathrm{C}_{2} \mathrm{H}_{5} + \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{CH}_{3} \mathrm{COOH} + \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\) Kolbe's electrolysis (produces ethane): \(\mathrm{CH}_{3} \mathrm{COO}^{-} \rightarrow \mathrm{CH}_{3} - \mathrm{CH}_{3} + 2 \mathrm{CO}_{2} + 4 \mathrm{H}^{+}\) Thus option (c) is the correct answer. The other options are not presented.
04

Conclusion

The correct ester that produces ethane after hydrolysis and subsequent Kolbe's electrolysis is option (c) \(\mathrm{CH}_{3} \mathrm{COO} \mathrm{C}_{2} \mathrm{H}_{5}\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Kolbe's Electrolysis
Kolbe鈥檚 Electrolysis is a fascinating electrochemical reaction where the salts of carboxylic acids are subjected to electrolysis in an aqueous solution. This technique was named after the pioneering chemist, Hermann Kolbe. The process is notable for its ability to produce alkanes by the decarboxylation of these acids鈥� salts. During electrolysis, carboxylate ions (\(\mathrm{RCOO}^{-}\)) are deprotonated, leading to the formation of free radicals. These radicals quickly pair up to form alkanes.Here's a quick rundown:
  • The procedure starts with the carboxylate ions losing a carbon dioxide molecule.
  • Free radicals are generated which are unstable and tend to form bonds with each other.
  • This reaction mechanism effectively results in the formation of an alkane gas.
What makes Kolbe鈥檚 Electrolysis particularly interesting is its industrial application, as it provides a direct method to transform renewable resources into valuable hydrocarbons like ethane.
Carboxylic Acid Production
Carboxylic acid production is an integral chemical process often initiated by the hydrolysis of esters. This transformations allows for a plethora of organic reactions, most prominently featuring Kolbe's Electrolysis.In the process of hydrolysis:
  • Esters react with water.
  • They break down into carboxylic acids and alcohols.
  • This takes place under acidic or basic conditions, using either an acid or base as a catalyst.
For instance, the ester \(\mathrm{CH}_{3} \mathrm{COO} \mathrm{C}_{2} \mathrm{H}_{5}\) when hydrolyzed produces acetic acid \(\mathrm{CH}_{3} \mathrm{COOH}\) and ethanol. This acetic acid can further participate in other reactions such as Kolbe鈥檚 Electrolysis to produce useful hydrocarbons.
Chemical Reaction Analysis
Analyzing chemical reactions typically involves understanding the transformation pathways and end products. In organic chemistry, especially with reactions involving esters and carboxylic acids, analysis focuses on reaction mechanisms, balance of equations, and product identification.For analyzing the ester hydrolysis and Kolbe鈥檚 Electrolysis, we consider:
  • The initial structure of the ester and its breakdown products.
  • Balancing of chemical equations to ensure matter conservation.
  • Tracking specific products formed in each reaction stage.
For example, identify the ester \(\mathrm{CH}_{3} \mathrm{COO} \mathrm{C}_{2} \mathrm{H}_{5}\) as a precursor that upon hydrolysis divides into acetic acid and ethanol. Recognizing acetic acid as capable of forming ethane through Kolbe鈥檚 Electrolysis allows us to predict the final outcome accurately. Each step in these reactions needs careful balancing to maintain consistent chemical integrity, ensuring insights into the reaction's efficacy and product yield.

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Most popular questions from this chapter

\(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{C}=\mathrm{CH}_{2}+\mathrm{ICl} \rightarrow\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CClCH}_{2} \mathrm{I}\) is an example of (a) anti Markovnikov addition to the double bond (b) a regioselective reaction (c) an electrophilic substitution reaction (d) a stereospecific reaction

Which of the following compounds can exhibit geometrical isomerism? (a) \(\mathrm{IBrC}=\mathrm{CFCI}\) (b) Cinnamic acid (c) Benzophenone oxime (d)

Identify the name of reactions (A) - (D) given below (A) \(2 \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{I} \stackrel{\text { Na /ether }}{\longrightarrow} \mathrm{C}_{4} \mathrm{H}_{10}+2 \mathrm{NaI}\) (B) (C) \(\mathrm{R}_{2} \mathrm{CuLi} \stackrel{\mathrm{R}^{\prime} \mathrm{X}}{\longrightarrow} \mathrm{R}-\mathrm{R}\) (D) \(\mathrm{CH}_{3}-\mathrm{CO}-\mathrm{CH}_{3} \stackrel{\mathrm{Zn}-\mathrm{Hg} / \mathrm{HCl}}{\longrightarrow} \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{3}\) (a) (A) Ulmann reaction (B) Electrolytic cleavage (C) Grignard reaction (D) Wolff-kishner reduction (b) (A) Wurtz reaction (B) Kolbe's electrolysis (C) Corey-House synthesis (D) Clemmensen reaction (c) (A) Wurtz reaction (B) Decarboxylation (C) Frankland reaction (D) Clemmensen reduction (d) (A) Wurtz-Fittig reaction (B) Decarboxylative coupling (C) Corey-House synthesis (D) Clemmensen reduction

When 3-methyl-2-butanol reacts with HBr, the expected product is 2-bromo-3-methyl-butane. But the actual product formed is 2 -bromo-2-methylbutane. Account for this.

Directions: Each question contains Statement-1 and Statement-2 and has the following choices (a), (b), (c) and (d), out of which ONLY ONE is correct. (a) Statement- 1 is True, Statement- 2 is True; Statement- 2 is a correct explanation for Statement-1 (b) Statement- 1 is True, Statement- 2 is True; Statement- 2 is NOT a correct explanation for Statement-1 (c) Statement-1 is True, Statement- 2 is False (d) Statement- 1 is False, Statement- 2 is True Statement 1 Oxymercuration reduction of an alkene gives an alcohol in which the -OH group is added to a more branched carbon of the double bond, while hydroboration- oxidation of an alkene gives an alcohol in which the -OH group is added to a less branched carbon of the alkene. and Statement 2 Hydration of an alkene in the presence of an acid is one of the standard methods of preparation of an alcohol form alkenes.
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