For each of the following compounds, draw the form that predominates at pH = 3, pH = 6, pH = 10, and pH = 14:
c. CF₃CH₂OH (pK_a= 12.4)

검증된 단계별 안내

Step 1: Understand the relationship between pH and pKa. The pKa of a compound is the pH at which half of the compound exists in its protonated form and half in its deprotonated form. When pH < pKa, the protonated form predominates. When pH > pKa, the deprotonated form predominates.

Step 2: Identify the functional group in CF3CH2OH. The compound contains an alcohol (-OH) group, which can lose a proton to form an alkoxide ion (-O⁻). The pKa of the alcohol group is given as 12.4.

Step 3: Analyze the compound at pH=3. Since pH=3 is much lower than the pKa (12.4), the protonated form (CF3CH2OH) will predominate because the environment is highly acidic.

Step 4: Analyze the compound at pH=6 and pH=10. Both pH values are still below the pKa (12.4), so the protonated form (CF3CH2OH) will continue to predominate, though at pH=10, a small fraction of the compound may start to deprotonate.

Step 5: Analyze the compound at pH=14. Since pH=14 is much higher than the pKa (12.4), the deprotonated form (CF3CH2O⁻) will predominate because the environment is highly basic.

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주요 개념

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Acid-Base Chemistry

Acid-base chemistry involves the study of proton transfer reactions, where acids donate protons (H+) and bases accept them. The pH scale measures the acidity or basicity of a solution, with lower values indicating higher acidity. Understanding how compounds behave as acids or bases at different pH levels is crucial for predicting their predominant forms in solution.

pKa and its Significance

The pKa value is a quantitative measure of the strength of an acid in solution, representing the pH at which half of the acid is dissociated. A lower pKa indicates a stronger acid. In this context, the pKa of 12.4 for CF3CH2OH suggests that at pH values below this, the compound will predominantly exist in its protonated form, while at higher pH values, it will be deprotonated.

Protonation and Deprotonation

Protonation refers to the addition of a proton to a molecule, while deprotonation is the removal of a proton. The predominant form of a compound at a given pH depends on its pKa relative to the pH. For CF3CH2OH, at pH 3 and 6, it will be mostly protonated, while at pH 10 and 14, it will be predominantly deprotonated, reflecting its behavior as a weak acid.

For each of the following compounds, draw the form that predominates at pH = 3, pH = 6, pH = 10, and pH = 14:c. CF3CH2OH (pKa = 12.4)