Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry

Bruice8th EditionOrganic ChemistryISBN: 9780135213711Non è quello che usi tu?Cambia libro di testo

Bruice 8th Edition

Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry

Problema 34a,b

Capitolo 2, Problema 34a,b

For each of the following compounds, indicate the atom that is protonated when an acid is added to a solution of the compound.
a.
b.

Guida verificata passo dopo passo

Step 1: Analyze the structure of compound A. It contains a carbonyl group (C=O) and an ether group (-O-). The oxygen atoms in these functional groups are potential sites for protonation because they have lone pairs of electrons that can interact with a proton (H⁺).

Step 2: Determine which oxygen atom in compound A is more likely to be protonated. The carbonyl oxygen is more electronegative and has a higher electron density compared to the ether oxygen. Additionally, protonation of the carbonyl oxygen leads to resonance stabilization, making it the preferred site for protonation.

Step 3: Analyze the structure of compound B. It contains a carbonyl group (C=O) and an amine group (-NH). Both the oxygen in the carbonyl group and the nitrogen in the amine group are potential sites for protonation due to their lone pairs of electrons.

Step 4: Compare the likelihood of protonation for the oxygen and nitrogen atoms in compound B. The nitrogen atom in the amine group is more basic than the oxygen atom in the carbonyl group, meaning it is more likely to accept a proton. Protonation of the nitrogen atom does not disrupt resonance, making it the preferred site for protonation.

Step 5: Summarize the findings. In compound A, the carbonyl oxygen is protonated when an acid is added. In compound B, the nitrogen in the amine group is protonated when an acid is added.

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Protonation

Protonation is the addition of a proton (H⁺) to a molecule, which can significantly alter its chemical properties. In organic chemistry, understanding which atom is protonated helps predict the behavior of the compound in acidic conditions. Typically, protonation occurs at sites with high electron density, such as lone pairs on nitrogen or oxygen atoms.

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Proton Splitting

Acidity and Basicity

Acidity refers to the ability of a compound to donate protons, while basicity is the ability to accept protons. The strength of an acid is often determined by the stability of its conjugate base after proton donation. In the context of the given compounds, identifying the most basic site will indicate where protonation is likely to occur when an acid is added.

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Understanding the difference between basicity and nucleophilicity.

Resonance Stabilization

Resonance stabilization occurs when a molecule can be represented by multiple valid Lewis structures, leading to increased stability. In the context of protonation, resonance can influence which atom is more favorable for protonation, as the resulting cation may be stabilized by delocalization of charge. This concept is crucial for predicting the outcome of acid-base reactions in organic compounds.

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The radical stability trend.

Pratica correlata

Domanda del libro di testo

Fosamax (shown on the previous page) has six acidic groups. The active form of the drug, which has lost two of its acidic protons, is shown in the box.

(Notice that the phosphorus atom in Fosamax and the sulfur atom in [Problem 36] can be surrounded by more than eight electrons because P and S are below the second row of the periodic table.)

a. Why are the OH groups bonded to phosphorus the strongest acids of the six groups?

b. Which of the remaining four groups is the weakest acid?

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Domanda del libro di testo

For each of the following compounds, indicate the atom that is protonated when an acid is added to a solution of the compound.

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Domanda del libro di testo

Using the table of pK_a values given in [Appendix I], answer the following:

a. Which is the most acidic organic compound in the table?