Aprendiendo a Distancia

With autumn looming on the horizon, the leaves on some trees have already begun the transition towards the vibrant hues of autumn. Whilst this change may outwardly seem like a simple one, the many vivid colours are a result of a range of chemical compounds, a selection of which are detailed here.


Before discussing the different compounds that lead to the colours of autumn leaves, it’s worth discussing how the colours of these compounds originate in the first place. To do this we need to examine the chemical bonds they contain – these can be either single bonds, which consist of one shared pair of electrons between adjacent atoms, or double bonds, which consist of two shared pairs of electrons between adjacent atoms. The colour causing molecules in autumn leaves contain systems of alternating double and single bonds – this is referred to as conjugation. A large amount of conjugation in a molecule can lead to them being able to absorb wavelengths of light in the visible spectrum. This leads to the appearance of colour.

Bartosz Grzybowski of Northwestern University in Illinois, US – who has already established himself as one of our most inventive chemists – has unveiled a ‘chemo-informatic’ scheme, Chematica, that can stake a reasonable claim to being paradigm-changing. Grzybowski and his colleagues have spent years assembling the transformations that link chemical species into a vast network that codifies and organises the known pathways through chemical space. The nodes of the network – molecules, elements and chemical reactions – are linked together by connecting reactants to products via the nexus of a known reaction. The full network contains around 7 million compound nodes and about the same number of reaction nodes. Grzybowski calls it a ‘collective chemical brain’.

The automatic chemist
Philip Ball

Chemistry World 22 August 2012

http://www.rsc.org/chemistryworld/2012/08/automatic-chemist