Organic chemistry: a beginning

The tutor knew that eventually, he would discuss organic chemistry.  While it might be mentioned only briefly in high school, it is important at university.

Organic chemistry is a bit different from the chemistry most students are first taught. Yet, in real life, organic chemistry is a much bigger field.  Plastics, drugs, insecticides – they’re all organic.

Here, we need to clarify a definition.  “Organic” now has two meanings.  The grocers and naturalists define it as “natural.”

To a chemist, however, “organic” means “carbon-based.”  Hence, from a chemist’s point of view, DDT is organic.

Recently the two definitions came into direct conflict when one of my students said her water was “organic.”  What she meant, of course, was that the water was “from a natural source.”  From a chemistry point of view, though, you can’t have organic water.  Being H2O, water is not carbon based.

Organic chemistry is a huge topic. In the beginning, nomenclature (how to name the compounds) is the focus. We’ll start today with some of that.

An alkane is an organic compound with only single bonds between the carbons. If it’s an alkane, but nothing more besides, then it just contains carbons and hydrogens. An example is propane:

This compound is propane because it has three carbons. Each joining line is a bond. Carbon makes four bonds and hydrogen makes only one, which dictates the structure of an alkane once you know how many carbons it has. You can tell an alkane because it ends in “ane”.

As the number of carbons grows, different arrangements become possible. For example, here are two possibilites for pentane:

Both structues are pentane since both have five carbons. Alkanes are named by how many carbons they contain as follows:

number of carbons name of alkane
1 methane
2 ethane
3 propane
4 butane
5 pentane
6 hexane
7 heptane
8 octane
9 nonane
10 decane

There is much more to say about organic chemistry, even at the high school level. For further discussion, see future posts:)

Source: Solomons, T.W. Graham. Organic Chemistry, 4th edition. 1988: John Wiley & Sons, Inc.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

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