 | This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Derivatization" – news ·newspapers ·books ·scholar ·JSTOR(December 2015) (Learn how and when to remove this message) |
Derivatization is a technique used inchemistry which converts achemical compound into aproduct (the reaction'sderivate) of similar chemicalstructure, called aderivative.
Generally, a specificfunctional group of the compound participates in the derivatization reaction and transforms theeduct to a derivate of deviatingreactivity,solubility,boiling point,melting point,aggregate state, or chemical composition. Resulting new chemical properties can be used forquantification orseparation of the educt.
Derivatization techniques are frequently employed inchemical analysis of mixtures and insurface analysis, e.g. inX-ray photoelectron spectroscopy where newly incorporated atoms label characteristic groups.
Several characteristics are desirable for a derivatization reaction:
Some examples of good derivatization reactions are the formation of esters and amides via acyl chlorides.
Classical qualitative organic analysis usually involves reacting an unknown sample with various reagents; a positive test usually involves a change in appearance — color, precipitation, etc.
These tests may be extended to give sub-gram scale products. These products may be purified by recrystallization, and their melting points taken. An example is the formation of 2,4-dinitrophenylhydrazones from ketones and2,4-dinitrophenylhydrazine.
By consulting an appropriate reference table such as in Vogel's, the identity of the starting material may be deduced. The use of derivatives has traditionally been used to determine or confirm the identity of an unknown substance. However, due to the wide range of chemical compounds now known, it is unrealistic for these tables to be exhaustive. Modern spectroscopic and spectrometric techniques have made this technique obsolete for all but pedagogical purposes.
Colorimetric detection after separation by liquidchromatography is an established method e.g. in amino acid analysis. So-called post-column derivatisation withNinhydrin as the active reagent can be used in HPLC systems directly after the separation column. Secondary amines react with ninhydrin to a blue iminium salt, while primary amines form a yellow product with ninhydrin. This principle is especially common in amino acid analysators[1], specialized HPLC-systems for the detection of free amino acids, also because in feed industry the use of post-column derivatisation is mandatory.[2]
Polar N-H and O-H groups on which give hydrogen bonding may be converted to relatively nonpolar groups on a relatively nonvolatile compound. The resultant product may be less polar, thus more volatile, allowing analysis bygas chromatography. Bulky, nonpolar silyl groups are often used for this purpose.[3]
Chiral derivatizing agents react with enantiomers to give diastereomers. Since diastereomers have different physical properties, they may be further analyzed byHPLC andNMR spectroscopy.