Nomenclature, representation of chemical structures and basic terminology

Chapter 5 Nomenclature, representation of chemical structures and basic terminology



Chapter contents


The functional groups 29

Naming compounds with a hydrocarbon backbone 30

Naming aromatic compounds 31

Naming isomers 31

Naming sugars 31

Naming lipids 32

Further shorthand 32

R groups 32

Two-dimensional representations of threedimensional shapes 33

Some general terminology 33

Naming orthodox medication 33

You now know how atoms join together to form larger, more complex molecules. The more complex the molecule the more difficult it becomes to draw. It is, however, possible to describe the structure of a compound no matter how big it is. So how are these diverse chemicals differentiated from one another?


The system of words used to name compounds is called nomenclature. The International Union of Pure and Applied Chemistry (IUPAC) has developed a standard approach to naming compounds.


You are unlikely ever to be called on to name a compound, but you might well see compounds named in scientific papers or pharmacology books. Although at first this might seem overwhelming, particularly if the compound is very complex, it is not as bad as it seems. The standardized naming system incorporates a logical numbering system, which, like shorthand, enables someone familiar with the system to visualize the precise structure of even the most complex compound.


On occasions, you might see the old-style nomenclature that was used before the IUPAC system. This is still generally understood by the scientific community, despite the IUPAC system being the favoured one. In the course of this chapter this older system will also be discussed.



The Functional Groups


Figure 5.1 demonstrates the different types of functional groups you are likely to see. Each of these functional groups has a characteristic chemical reaction. It is not necessary for you to know these in detail, but it is helpful to appreciate them with regards to a particular pharmacological activity.


image

Figure 5.1 Common functional groups encountered in pharmacology.


Shorthand can sometimes be used for the chemical formulae of short functional groups such as:


• CH3: the methyl group can be represented as Me.

• C2H5: the ethyl group is represented as Et

There can be quite a variety of these; with a little deduction they are fairly obvious.


Many of these functional groups will be attached to a hydrocarbon backbone, which is composed of carbon and hydrogen atoms (see Chapter 4 ‘Bonds: continued’, p. 24).

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Jul 22, 2016 | Posted by in PHARMACY | Comments Off on Nomenclature, representation of chemical structures and basic terminology

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