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How can naphthalene, salicylic acid, and salicylaldehyde be identified chemically?

We often encounter these compounds in separation or synthesis byproduct analyses. While spectroscopic methods are definitive, I need bench-level, wet-chemical tests for a quick preliminary confirmation. Understanding the logic behind the tests for phenolic, acidic, and aldehyde groups in this context is crucial for my students and my own procedural validation.

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By Akshatha Patel Answered 1 year ago

From my experience in teaching organic qualitative analysis, you need a strategic sequence targeting distinct functional groups. First, test solubility in sodium bicarbonate; only salicylic acid (a carboxylic acid) will bubble due to CO?. Next, with the remaining two, perform a Tollens’ or Fehling’s test; salicylaldehyde (an aldehyde) will give a silver mirror or red precipitate, while naphthalene, an inert hydrocarbon, will not react in either. I always recommend this order to avoid false positives from the aldehyde’s slight acidity. It’s a classic and reliable bench method.

 

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