As mentioned in the previous post, the experiment editor for the Green Lab Notebook app is fleshing out. At this point, the quantity blocks are now fully operational, and they are followed up by a block describing the green chemistry metrics that are pertinent to the reaction.
First up, editing any of the measured values for experimental quantities such as mass, volume, moles, etc., triggers a cascade of interdependent calculations which fill out any available theoretical amounts for other properties within the component, or other components that are related by ratio of stoichiometry. This is very similar to the functionality offered by the Yield101 app, although the user interface is different.
Once there is enough information provided to gain information about enough of the components, three green chemistry metrics are calculated:
- process mass intensity (PMI): total mass of input materials (including reactants, solvents, catalysts, etc.) divided by the total mass of the desired products as-isolated; all other things being equal, lower PMI values are better and 1 is perfect
- E-factor: total mass of waste products divided by the total mass of isolated products; all other things being equal, lower is better and 0 means that there is no waste at all
- atom efficiency: total molecular weight of products divided by total molecular weight of reactants (adjusted for stoichiometry); this is an intrinsic property of the balanced reaction equation, and a value of 100% means that all of the atoms in the reactants were also incorporated into the product, which is a good thing
These handy metrics are an always-on feature, so that as scientists fill in the data for their chemical reactions, the green chemistry properties are displayed as soon as there is enough information to calculate them:
While these are incredibly trivial calculations, they are only possible when the information is actually available. This in turn requires each reaction component to be identified, classified, and quantified in a way that allows mass (in standard units) to be calculated, and also get the molecular weight right (which most cheminformatics software cannot guarantee).
The green chemistry summary block is intended to be followed up by some other useful readouts, too, for example automatically retrieved green solvent information, quick reference information about sustainability of input feedstocks, and hazard/toxicity/other environmental malignancy issues for any of the compounds involved. Some of these will take a bit more infrastructure to be built out first.