Formulae, functional groups and isomers

This page contains relevant information for both Level 2 and 3 Carbon chemistry

Structural formulae

In chemistry different formulae are used including empirical and molecular formulae, and in Carbon chemistry: structural formula , and their abbreviated version: condensed structural formulae.

Scan the QR coder above for information on empirical and molecular formulae or click here

In carbon chemistry we are concerned with the structures of the organic compound - we use structural formulae. To save space, condensed structural formulae are used. Further shorthand versions called skeleton / line structures can be drawn.

Kekulé, in 1856, linked the number of valence electrons to the number of bonds an atom can form. Here are some important atoms that you will come across in organic chemistry indicating the number of bonds they form.

carbon chemistry formulae differences

functional groups

naming organic molecules

At this stage you should know the rules for naming hydrocarbon chains with regards to the number of carbons in a chain, but here is a quick recap.

Naming rules and steps

This table is applicable to both L2 and L3 Chemistry.

Some of the functional groups do not need to be known at L2 chemistry. The following are the functional group compounds that need to be known at L2 chemistry:

alkanes, alkenes, alkynes, haloalkanes, primary amines, alcohols, and carboxylic acids.

This means, in addition to the above, the following need to known at L3:

alkene, haloalkane, amine, alcohol, aldehyde, ketone, carboxylic acid, ester (including triglycerides), acyl chloride, and amide.

functional groups and introduction to naming compounds

naming carbon compounds

GUIDE TO NAMING COMPOUNDS

isomers

There are 2 types of isomers you need to know about at this level:

Structural isomers

Stereoisomers

structural isomers

stereoisomers

RECAP WITH REGARDS TO STEREO-ISOMERS:

* at Level 2 chemistry you need to be able to identify geometric (cis and trans) isomers

* at level 3 chemistry you need to be able to identify optical isomers (enantiomers).

Geometric (cis and trans) isomers have two requirements:

1) a carbon carbon double bond (C = C), which cannot rotate

2) different atoms / groups of atoms attached to each of the carbon atoms either side of the double covalent bond.

If both these requirements are met then cis and trans isomerism will be exhibited

Optical isomers can be identified by the presence of a chiral, or asymmetric, carbon in a molecule. They are mirror images of each other; they are non superimposable.

*Chirality (having a chiral carbon) means that there are four different atoms / groups of atoms bonded to a carbon atom

For further information on optical isomers, applicable for L3 chemistry, click here,

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