# Is Nitroglycerine a Nitro Compound or an Ester?

I looked up nitroglycerine in a science dictionary (Oxford Dictionary of Science, 2003), and it explicitly mentions that nitroglycerine is an ester and not a nitro compound.

However my teacher told us in class, that nitroglycerine is a nitro compound (She didn't say it wasn't an ester though …).

The definition for a nitro compound (courtesy Wikipedia) is:

Nitro compounds are organic compounds that contain one or more nitro functional groups ($\ce{−NO2}$).

Assuming that definition is correct, as well and looking at the structure of nitroglycerine, it appears (to me) that nitroglycerine is both an ester and a nitro compound.

So who's right here?

## 1 Answer

The Oxford dictionary is correct.

A nitro compound is defined by the $\ce{-NO2}$ functional group, but only if that group is attached to a carbon atom. Once an additional oxygen is added, the molecule is basically inorganic nitrate and thus belongs to a wildly different compound class.

You think that is confusing? Well, an alcohol is defined by a hydroxy group — but only if that hydroxy group is attached to a carbon, which in turn is not attached to a different oxygen, nitrogen or sulphur atom, and which is not part of an aromatic system. Even more constraints in there.

• According to the Blue Book and the Glossary of class names, nitro compounds contain a $\ce{-NO2}$ group that can be attached to any atom. Thus, nitrates are nitro compounds. However, it is correct that, without further specifications, carbon-nitro compounds are usually implied. Furthermore, nitro compounds are not necessarily named by means of the prefix ‘nitro’. In particular, it is correct that nitroglycerine is systematically named as ester of nitric acid (i.e. nitrate). – Loong Aug 30 '16 at 20:52