Using metrics and sustainability considerations to evaluate the use of bio-based and
non-renewable Brønsted acidic ionic liquids to catalyse Fischer esterification reactions
James H. Clark,* Thomas J. Farmer, Duncan J. Macquarrie and James Sherwood
Additional data files
Metrics calculations: The following tables record examples the mass input and output of the reactions discussed in the
main article. These values were used to calculate the reaction metrics. Table 1a describes the use of [H-NMP][HSO4] and
the use of [H-NMP][OCym] in the synthesis of benzyl acetate in terms of mass utilisation. Table 2a describes the use of [HNMP][OCym] in the synthesis of ethyl levulinate acetate in terms of mass utilisation but also incorporating the synthesis
of the catalyst.
Table 1a Reaction mass input and output for the synthesis of benzyl acetate
Substance
[H-NMP][HSO4]
[H-NMP][OCym]
Mass /g
Contribution
Mass /g
Contribution
Acetic acid
0.721
27.6%
0.721
1.8%
Benzyl alcohol
1.30
49.7%
1.30
3.2%
Diethyl ether
0
0%
7.13
17.8%
Water
0
0%
30.0
74.8%
0.592
22.7%
0.940
2.3%
0.944
(52% yield)
0.697
(39% yield)
Reactants
Solvents
Catalysts
[NMP][HSO4] or [H-NMP][OCym]
Desired product
Benzyl acetate
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Table 2a Reaction mass input and output for the synthesis of ethyl levulinate with N-methyl pyrrolidinonium pcymene-2-sulphonate
Excluding [H-NMP][OCym] synthesis
Including [H-NMP][OCym] synthesis
Mass /g
Contribution
Mass /g
Contribution
Ethanol
0.553
11.3%
0.553
1.6%
Levulinic acid
0.464
9.5%
0.464
1.3%
3.57
72.8%
3.57
10.2%
Ammonium bromide
0.0167
0.05%
Glutamic acid
0.397
1.1%
Methanol
0.671
1.9%
Essential oil of orange
0.928
2.6%
Montmorillonite clay
0.132
0.38%
Oleum
0.500
1.4%
Palladium on carbon
0.0705
0.20%
Water
25.1
71.6%
2.66
7.6%
0.290
(50% yield)
Substance
Reactants
Solvents
Diethyl ether
Catalyst: NMP reactant
Catalyst: p-CSA reactant
Catalyst synthesis
Dichloromethane
[H-NMP][OCym]
0.313
6.4%
0.290
(50% yield)
Desired product
Ethyl levulinate
Regulatory issues surrounding NMP: With the introduction of the REACH legislation in Europe, some
traditional solvents are being subjected to restrictions on their use. Because of its reproductive toxicity, one of
the solvents now classified as a substance of very high concern (SVHC) is NMP [1]. It also causes serious eye
and respiratory irritation [2]. This has implications for the use of NMP directly as a solvent, but also the use of
NMP as an intermediate in the synthesis of Brønsted acidic ionic liquids now comes into question. The
relationship between chemical structure and toxicity is not a precise one, and is not necessarily systematic
across a family of related compounds in a predictable way. For example, the liquid 1-butyl-4carboxypyrrolidinone methyl ester has been recently described as “harmless to human health” and so future
generations of amide solvents, compliant with chemical legislation, may come to exist [3]. In turn, these
solvents may be used to produce novel Brønsted acidic ionic liquids.
References
1.
http://echa.europa.eu/candidate-list-table, accessed 8/11/2013.
2.
MSDS, 1-methylpyrrolidinone
3.
Moity L, Molinier V, Benazzouz A, Barone R, Marion P, Aubry JM: In silico design
of bio-based commodity chemicals: Application to itaconic acid based solvents.
Green Chem 2013, advanced article. DOI: 10.1039/c3gc41442f.
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