Final answer:
In a carbinolamine formation reaction that's acid-catalyzed, sulfuric acid or phosphoric acid are likely the sources of protons, being commonly used strong acids in laboratory settings for similar reactions.
Step-by-step explanation:
The protonation reaction in carbinolamine formation is an acid-catalyzed process. Although no acid was added in the lab procedure described, it's possible that the reaction implicitly relies on an acid present within the reagents or the environment. Based on the information provided, the plausible sources of acid that could catalyze the reaction include the strong acids such as sulfuric acid or phosphoric acid as indicated in the synthesis of aspirin and in the conversion of carboxylic acids to their reactive derivatives. These acids are typically used in laboratory settings to catalyze similar reactions due to their ability to effectively donate protons. Although hydrochloric acid and acetic acid are also acids, sulfuric and phosphoric acid are more commonly used in such acid-catalyzed laboratory reactions.