Guides and metrics: Solvent selection guides

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 (colour 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 colour code (green, yellow, red). It was thus easy to compare the colour code of each solvent in the different guides (Table 1).

 

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.

Table 1: Ranking comparison (extract)

Family

Solvent

AZ

GCI-PR

GSK

Pfizer

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

This colour 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 is reproduced 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.

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.

  1. D. Prat, J. Hayler and A. Wells, A survey of solvent selection guides, Green Chem., 2014, 16, 4546–4551.