In alkaline solutions, amino acids act as acids, donating a proton (H+) from their carboxyl group (-COOH).
Detailed Explanation
Amino acids possess both an acidic carboxyl group (-COOH) and a basic amino group (-NH2). This amphoteric nature allows them to behave as either acids or bases depending on the pH of the solution.
Behavior in Alkaline Conditions
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Deprotonation of the Carboxyl Group: In an alkaline (high pH) environment, the concentration of hydroxide ions (OH-) is high. These hydroxide ions react with the carboxyl group of the amino acid, leading to the removal (deprotonation) of a proton (H+).
- -COOH + OH- --> -COO- + H2O
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Formation of a Negatively Charged Ion: The deprotonation of the carboxyl group results in the formation of a negatively charged carboxylate ion (-COO-).
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Amino Group Remains Mostly Unchanged: While the amino group could theoretically be deprotonated at extremely high pH levels, under typical alkaline conditions, it remains largely protonated (-NH3+).
Summary of Changes
| Feature | Before (Neutral/Acidic) | After (Alkaline) |
|---|---|---|
| Carboxyl Group | -COOH | -COO- |
| Amino Group | -NH3+ | -NH3+ (mostly) |
| Overall Charge | Depends on pH | Negative |
Acting as an Acid
The ability of the amino acid to donate a proton from its carboxyl group in the presence of a base (like hydroxide ions in an alkaline solution) demonstrates its acidic behavior. The amino acid is effectively neutralizing the base by providing a proton.
