Again developed by GSK,iv the reaction mass efficiency takes into account atom economy, chemical yield and stoichiometry. The formula can take one of the two forms shown below:
From a generic reaction where A + B → C Reaction mass efficiency = molecular weight of product C × yield m.w. A + (m.w. B × molar ratio B/A)
Or more simply Reaction mass efficiency = mass of product C × 100 / mass of A + mass of B
Like carbon efficiency, this measure shows the “clean-ness” of a reaction but not of a process, for example, neither metric takes into account waste produced. For example, these metrics could present a rearrangement as “very green” but they would fail to address any solvent, work-up and energy issues arising.
Read more about this topic: Green Chemistry Metrics
Famous quotes containing the words reaction, mass and/or efficiency:
“The excessive increase of anything often causes a reaction in the opposite direction.”
—Plato (c. 427–347 B.C.)
“Life is a series of diminishments. Each cessation of an activity either from choice or some other variety of infirmity is a death, a putting to final rest. Each loss, of friend or precious enemy, can be equated with the closing off of a room containing blocks of nerves ... and soon after the closing off the nerves atrophy and that part of oneself, in essence, drops away. The self is lightened, is held on earth by a gram less of mass and will.”
—Coleman Dowell (1925–1985)
“Nothing comes to pass in nature, which can be set down to a flaw therein; for nature is always the same and everywhere one and the same in her efficiency and power of action; that is, nature’s laws and ordinances whereby all things come to pass and change from one form to another, are everywhere and always; so that there should be one and the same method of understanding the nature of all things whatsoever, namely, through nature’s universal laws and rules.”
—Baruch (Benedict)