Ch. 2 - Acids and Bases; Functional Groups

Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook

Wade 9th Edition

Ch. 2 - Acids and Bases; Functional Groups

Problem 13j

Chapter 2, Problem 13j

Write equations for the following acid–base reactions. Label the conjugate acids and bases, and show any inductive stabilization. Predict whether the equilibrium favors the reactants or products. Try to do this without using a table of pKa values, but if you need a hint, you can consult Appendix 4.
j. CF₃CH₂O^– + FCH₂CH₂OH

Verified step by step guidance

Identify the acid and base in the reaction. In this case, CF3CH2O- is the base and FCH2CH2OH is the acid. The base will accept a proton from the acid.

Write the chemical equation for the acid-base reaction:

{CF 3 CH 2 O}_{-} + F CH 2 CH 2 OH \to CF 3 CH 2 OH + {F CH 2 CH 2 O}_{-}

Label the conjugate acid and base. After the reaction, CF3CH2OH is the conjugate acid and FCH2CH2O- is the conjugate base.

Consider inductive effects for stabilization. The CF3 group is highly electronegative and can stabilize the negative charge on CF3CH2O- through inductive effects, making it a weaker base compared to FCH2CH2O-. This suggests that the equilibrium may favor the formation of CF3CH2OH and FCH2CH2O-.

Predict the direction of equilibrium. Without using pKa values, consider the stability of the conjugate base and acid. The inductive effect of the CF3 group suggests that the equilibrium will favor the products, as CF3CH2OH is a weaker acid compared to FCH2CH2OH.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Acid-Base Reaction Mechanism

Acid-base reactions involve the transfer of protons (H+) between molecules. The acid donates a proton, becoming its conjugate base, while the base accepts a proton, forming its conjugate acid. Understanding the mechanism helps in identifying the reactants and products in the reaction, as well as labeling the conjugate acids and bases.

Inductive Effect

The inductive effect refers to the electron-withdrawing or electron-donating influence exerted by substituents through sigma bonds. In organic chemistry, electronegative groups like CF3 can stabilize or destabilize ions by affecting electron density, which can influence the acidity or basicity of molecules and the direction of equilibrium in acid-base reactions.

Equilibrium Prediction in Acid-Base Reactions

Predicting the direction of equilibrium in acid-base reactions involves assessing the relative stability of reactants and products. Factors such as inductive effects and resonance stabilization play a role. Generally, equilibrium favors the side with the more stable conjugate acid-base pair, which can be inferred without pKa values by considering molecular structure and stabilization effects.

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Determining Acid/Base Equilibrium

Related Practice

Textbook Question

Consider the type of orbitals involved, and rank the following nitrogen compounds in order of decreasing basicity. 2. Rank the conjugate acids in order of increasing acidity. (Hint: These two orders should be the same!)

Textbook Question

Like nitrogen and carbon, oxygen also shows this same hybridization effect on acidity. Both of the following compounds can lose a proton from a positively charged oxygen with three bonds to give a conjugate base containing a neutral oxygen with two bonds. One of these structures has pK_a= −2.4, while the other has pK_a= −8.0.

a. Show the reaction of each compound with water.

b. Match each structure with its pK_a, and explain your choice.

Textbook Question

Rank the following acids in decreasing order of their acid strength. In each case, explain why the previous compound should be a stronger acid than the one that follows it.

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Textbook Question

Write equations for the following acid–base reactions. Label the conjugate acids and bases, and show any inductive stabilization. Predict whether the equilibrium favors the reactants or products. Try to do this without using a table of pK_a values, but if you need a hint, you can consult Appendix 4.

g. NaOCH₂CH₃ + Cl₂CHCH₂OH

h. H₂Se + NaNH₂

i. CH₃CHFCOOH + FCH₂CH₂COO^–

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Textbook Question

Write equations for the following acid–base reactions. Label the conjugate acids and bases, and show any inductive stabilization. Predict whether the equilibrium favors the reactants or products. Try to do this without using a table of pKa values, but if you need a hint, you can consult Appendix 4.

a. CH₃CH₂OH + CH₃NH⁻

b. F₃CCOONa + Br₃C—COOH

c. CH₃OH + H₂SO₄

Textbook Question

For each of the following reactions, suggest which solvent(s) would be compatible with the acids and bases involved. (We will ignore any other possible reactions for now.) Your choices of solvents are pentane, diethyl ether, ethanol, water, and ammonia. Refer to Appendix 4 for any needed values of pK_a, or estimate them.

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