Survey of Solvent Selection Guides

In the previous lesson differences in structure and weighting of HSE criteria in published solvent selection guides were discussed. Initial work carried out by the CHEM21 project included building a methodology to compare the 5 guides available (AZ, GCI-PR, GSK, Pfizer, Sanofi). This methodology, explained in the video, consists of a comparison of the rankings (color codes) of the 51 more represented solvents in these guides. For guides which did not offer a clear ranking (AZ, GSK, GCI-PR), the number of criteria was reduced to three: one for Safety, one for Health, one for Environment. For each guide, three solvent groups of similar size were built around the arithmetical mean, with a classical color code (green, yellow, red). It was thus easy to compare the color code of each solvent in the different guides (Table 1).

Table 1: Ranking comparison (extract)
Family Solvent AZ GCI-PR GSK Pfize Sanofi Overall*
Alcohols MeOH 19 14 14 Preferred Recommended TBC
EtOH 16 13 17 Preferred Recommended Recommended
i -PrOH 16 16 17 Preferred Recommended Recommended
n -BuOH 17 13 18 Preferred Recommended Recommended
t -BuOH 20 15 15 Preferred Subst. advisable TBC
Benzyl alcohol 11 20 Subst. advisable TBC
Ethylene glycol 13 21 Usable Subst. advisable TBC
Ketones Acetone 21 15 15 Preferred Recommended TBC
MEK 21 16 15 Preferred Recommended TBC
MIBK 22 17 15 Recommended TBC
Cyclohexanone 14 20 Subst. advisable TBC
Ethers Diethyl ether 27 21 3 Undesirable Banned Highly Hazardous
Diisopropyl ether 4 Undesirable Subst. advisable Hazardous
MTBE 24 21 4 Usable Subst. advisable TBC
THF 23 16 4 Usable Subst. advisable TBC
Me-THF 24 15 11 Usable Recommended Problematic
1,4-dioxane 28 21 11 Undesirable Subst. requested Hazardous
Anisole 18 13 18 Recommended Recommended
DME 21 23 2 Undesirable Subst. requested Hazardous

Table 1 is extracted from D. Prat, J. Hayler and A. Wells, A survey of solvent selection guides, Green Chem., 2014, 16, 4546-4551.It is copyright to the Royal Society of Chemistry (RSC) and is reproduced here with their express permission. If you wish to reproduce it elsewhere you must obtain similar permission from the RSC.

This color code comparison gave a clear agreement (large majority) for 34 of the 51 solvents (two thirds of solvents overall). Further discussion permitted the identification of the most hazardous solvents. One third of solvents could not be ranked (named “to be confirmed” in Table 1), thus reflecting the different weighting of criteria in the solvent guides [1] . The overall list is given in Table 2.

Table 2: Overall ranking of solvents
Combined rankingSolvent
Recommended Water, EtOH, i -PrOH, n -BuOH, EtOAc, i -PrOAc, n -BuOAc, anisole, sulfolane.
Recommended or problematic? MeOH, t -BuOH, benzyl alcohol, ethylene glycol, acetone, MEK, MIBK, cyclohexanone, MeOAc, AcOH, Ac 2 O.
Problematic Me-THF, heptane, Me-cyclohexane, toluene, xylenes, chlorobenzene, acetonitrile, DMPU, DMSO.
Problematic or hazardous? MTBE, THF, cyclohexane, DCM, formic acid, pyridine.
Hazardous Diisopropyl ether, 1,4-dioxane, DME, pentane, hexane, DMF, DMAc, NMP, methoxy-ethanol, TEA.
Highly hazardous Diethyl ether, benzene, chloroform, CCl 4 , DCE, nitromethane.