Blogging a crystal structure a day in 2014


Contributed by

Helen Maynard-Casely

Vinegar – acetic acid

What does it look like?

Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software

Image generated by the VESTA (Visualisation for Electronic and STructural analysis) software

What is it?

170px-AceticAcid012This is the molecule that gives the tang on your tongue when you add vinegar to your chips. Most vinegars have about 4-5 % acetic acid molecules in the mix. In pure form, acetic acid is known as 'glacial' acetic acid because of the snow-like white crystals it grows.

The image we've shown would seem a very over-simplified image of the crystal structure as it is missing the all-important four hydrogen atoms. However, as we've mentioned on the blog a few times before, finding hydrogen positions from X-ray diffraction is extremely challenging as they don't scatter very well. It would take a later neutron diffraction study to place where the hydrogen positions are in this material.

Where did the structure come from?

This arrangement of molecules came from a paper by Jones and Templeton, published in 1958. This is a very early determination of a molecular crystal structure, and the work built on information from other experimental methods, including spectroscopy.

Tags: acid   mineral   food