Derivatization is a technique used in chemistry

Chemistry

Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....

 which transforms a chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 into a product

Product (chemistry)

Product are formed during chemical reactions as reagents are consumed. Products have lower energy than the reagents and are produced during the reaction according to the second law of thermodynamics. The released energy comes from changes in chemical bonds between atoms in reagent molecules and...

 (the reaction's derivate) of similar chemical structure

Structure

Structure is a fundamental, tangible or intangible notion referring to the recognition, observation, nature, and permanence of patterns and relationships of entities. This notion may itself be an object, such as a built structure, or an attribute, such as the structure of society...

, called a derivative

Derivative (chemistry)

In chemistry, a derivative is a compound that is derived from a similar compound by some chemical or physical process. In the past it was also used to mean a compound that can be imagined to arise from another compound, if one atom is replaced with another atom or group of atoms, but modern...

.

Generally, a specific functional group

Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...

 of the compound participates in the derivatization reaction and transforms the educt to a derivate of deviating reactivity, solubility

Solubility

Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on...

, boiling point

Boiling point

The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....

, melting point

Melting point

The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...

, aggregate state, or chemical composition. Resulting new chemical properties can be used for quantification

Quantification

Quantification has several distinct senses. In mathematics and empirical science, it is the act of counting and measuring that maps human sense observations and experiences into members of some set of numbers. Quantification in this sense is fundamental to the scientific method.In logic,...

 or separation

Separation process

In chemistry and chemical engineering, a separation process, or simply a separation, is any mass transfer process used to convert a mixture of substances into two or more distinct product mixtures, at least one of which is enriched in one or more of the mixture's constituents. In some cases, a...

 of the educt.

Derivatization techniques are frequently employed in chemical analysis of mixtures and in surface analysis, e.g. in x-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy is a quantitative spectroscopic technique that measures the elemental composition, empirical formula, chemical state and electronic state of the elements that exist within a material...

 where newly-incorporated atoms label characteristic groups.

Derivatization reactions

Several characteristics are desirable for a derivatization reaction:

1. The reaction is reliable and proceeds to completion. Less unreacted starting material will simplify analysis. Also, this allows a small amount of analyte to be used.
2. The reaction is general, allowing a wide range of substrates, yet specific to a single functional group, reducing complicating interference.
3. The products are relatively stable, and form no degradation products within a reasonable period, facilitating analysis.

Some examples of good derivatization reactions are the formation of esters and amides via acyl chlorides.

Classical qualitative organic analysis

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 and 2,4-dinitrophenylhydrazine

2,4-Dinitrophenylhydrazine

2,4-Dinitrophenylhydrazine is the chemical compound C6H32NHNH2. Dinitrophenylhydrazine is relatively sensitive to shock and friction; it is a shock explosive so care must be taken with its use. It is a red to orange solid, usually supplied wet to reduce its explosive hazard...

.

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.

For gas chromatography

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 by gas chromatography. Bulky, nonpolar silyl groups are often used for this purpose.

Chiral derivatizing agent

Chiral derivatizing agents react with enantiomers to give diastereomers. Since diastereomers have different physical properties, they may be further analyzed by HPLC

High-performance liquid chromatography

High-performance liquid chromatography , HPLC, is a chromatographic technique that can separate a mixture of compounds and is used in biochemistry and analytical chemistry to identify, quantify and purify the individual components of the mixture.HPLC typically utilizes different types of stationary...

 and NMR spectroscopy

NMR spectroscopy

Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is a research technique that exploits the magnetic properties of certain atomic nuclei to determine physical and chemical properties of atoms or the molecules in which they are contained...

.