Question

What is the criterion of purity with respect to organic compounds?

Answer 1

`"Explain the criterion of purity with respect to organic compounds?"`

Explanation:

Well an organic molecule is the product of a chemical reaction, and the main product may be contaminated by other products from competing side reactions, or if the sample has not been appropriately worked up and dried, the organic molecule may contain some inorganic salt, or waters of hydration. The presence of water molecules is especially common.

And how to assess purity? Still the best means is by melting point determination. If you make a compound, you compare it to the literature value, which is (usually) taken from an extremely pure sample. If the melting points agree you gots a pure sample. The melting points will usually not agree, and you have to further purify and dry your sample. The standard phrase in this process, is `"recrystallized to constant melting point...."`

And note that sometimes you can have a sample of organic compound that is analytically pure, and when you take its NMR spectrum, you see traces of water or of the recrystallizing solvent.