# Why doesn't EDTA have a double bond?

EDTA (Ethylenediaminetetraacetic acid) has a structure like this

But why, as the name 'Ethylene' suggests, doesn't it should have a double bond between carbons?

## 1 Answer

A lot of non-systematic chemical names don't describe the composition of the compound, they describe what the compound is synthesised from. That is the case here since EDTA is derived from ethylene by adding two units of the diamine.

It isn't that uncommon in chemical names. Polyethylene, for example, is (simplifying only slightly) a long chain of carbons connected by single bonds. But it is made by polymerising ethylene. Hence has a name that doesn't describe what its structure is but where it came from.

• As far as trivial names are concerned, this is one possibility to describe it. Another one is that ethylene is the name for the subunit $\ce{C2H4}$. Just like methylene $\ce{CH2}$ in methylene dichloride ($\ce{CH2Cl2}$) or propylene ($\ce{C3H6}$) in propylene glycol. So it actually describes the structure and not the origin. Names for polymers, however, are always derived from the monomer(s). Apr 28 '14 at 3:49
• @Martin-マーチン, as I understand the matter, your comment is more accurate in this context. Jun 29 '15 at 13:07