Question

please give me exact details of how Semicarbazone derivatization works and how exactly you determine what product you have. Please write it clearly too

Answer 1

Semicarbazone is a derived product. The precursor for this product is aldehydes or ketones. The IUPAC name of this compound is  2,4-dinitrophenylhydrazone.

What is Derivatization?

We know that in qualitative analysis, we use different reagents to react them with the initial unknown compound. Based on the result of one test we go onto subsequent tests possible. This was usually a bit difficult and unreliable when the test compound used was available in small quantities only because the same compound cannot be reused for different tests. There came the idea of derivatization. In this complex petrochemical, samples are converted to other compounds by a simple and efficient reaction (As in our case precursor aldehydes or ketones are converted to semicarbazone.).These derivated compounds give better results when compared to the initial sample.

How does Semicarbazone derivatization work?

This derivated compound is generally used to check the product formed upon hydration. During this condensation, reaction water is eliminated as the side product. Based on the melting point of the products formed, the initial compound is predicted.

This prediction is based on the comparison known values of melting points of known semicarbazone products with the observed melting points. If the range of these melting points differences is narrow then it is considered to be purer. This melting point differences also enable us to predict the type of addition occurred. (whether Markovnikov or Anti-Markovnikov addition).

Note: All of this is possible because semicarbazide undergoes a condensation reaction with aldehydes and ketones.

Why is Semicarbazone derivatization preferred?

While there are other types of derivatizations like derivatizations of phenols or alcohols to esters, Semicarbazone derivatization generally enables us to faster analysis than the other.