Derivatization is a technique used in
chemistry which converts a
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
into a
product
Product may refer to:
Business
* Product (business), an item that serves as a solution to a specific consumer problem.
* Product (project management), a deliverable or set of deliverables that contribute to a business solution
Mathematics
* Produ ...
(the reaction's derivate) of similar chemical
structure, called a
derivative
In mathematics, the derivative of a function of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. ...
.
Generally, a specific
functional group
In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the re ...
of the compound participates in the derivatization reaction and transforms the
educt to a derivate of deviating
reactivity,
solubility
In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution.
The extent of the solub ...
,
boiling point,
melting point
The melting point (or, rarely, liquefaction point) of a substance 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 depen ...
,
aggregate state
Aggregate or aggregates may refer to:
Computing and mathematics
* collection of objects that are bound together by a root entity, otherwise known as an aggregate root. The aggregate root guarantees the consistency of changes being made within the ...
, or chemical composition. Resulting new chemical properties can be used for
quantification or
separation of the
educt.
Derivatization techniques are frequently employed in
chemical analysis
Analytical chemistry studies and uses instruments and methods to separate, identify, and quantify matter. In practice, separation, identification or quantification may constitute the entire analysis or be combined with another method. Separati ...
of mixtures and in
surface analysis
A surface, as the term is most generally used, is the outermost or uppermost layer of a physical object or space. It is the portion or region of the object that can first be perceived by an observer using the senses of sight and touch, and is ...
, e.g. in
X-ray photoelectron spectroscopy
X-ray photoelectron spectroscopy (XPS) is a surface-sensitive quantitative spectroscopic technique based on the photoelectric effect that can identify the elements that exist within a material (elemental composition) or are covering its surface, ...
where newly incorporated atoms label characteristic groups.
Derivatization reactions
Several characteristics are desirable for a derivatization reaction:
# 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.
# The reaction is general, allowing a wide range of substrates, yet specific to a single functional group, reducing complicating interference.
# 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-DNPH or DNPH) is the organic compound C6H3(NO2)2NHNH2. DNPH is a red to orange solid. It is a substituted hydrazine. The solid is relatively sensitive to shock and friction. For this reason DNPH is usually handle ...
.
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 and
NMR spectroscopy
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic fie ...
.
References
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Chemical processes