PFAS Environmental Reaction Library S

The PFAS Environmental Reaction Library has been developed as a component of the Chemical Transformation Simulator (CTS), a web-based software tool under development in EPA’s Office of Research and Development.  The library is implemented in CTS to predict the likely environmental transformation products of per- and polyfluoroalkyl substances (PFAS). 

Version 1.1 of the PFAS Environmental Reaction Library contains 59 reaction schemes:

Decarboxylation Schemes

Decarboxylation: Alpha carboxy ether to ether

Decarboxylation: Alpha hydroxy fluorotelomer carboxylic acid to fluorotelomer aldehyde

Decarboxylation: Beta carboxy ketone to methyl ketone

 

Desulfonation Scheme

Desulfonation: Fluorotelomer sulfonate to fluorotelomer alcohol

 

Epoxidation Scheme

Epoxidation: Alkene to epoxide_PTP

 

Hydrolysis Schemes

Hydrolysis: Acid fluoride to carboxylic acid

Hydrolysis: Alpha difluoro alcohol to acid fluoride

Hydrolysis: Alpha fluoro secondary alcohol to ketone

Hydrolysis: Amide to carboxylic acid

Hydrolysis: Beta hydroxy fluorotelomer iodide to diol_PTP

Hydrolysis: Carboxylic acid ester to carboxylic acid

Hydrolysis: Diperfluorophosphinate to perfluorophosphonate

Hydrolysis: Diphosphate ester to monophosphate ester

Hydrolysis: Epoxide to diol_PTP

Hydrolysis: Fluorotelomer acid to unsaturated telomer acid

Hydrolysis: Fluorotelomer iodide to fluorotelomer alcohol

Hydrolysis: Fluorotelomer urethane to fluorotelomer alcohol

Hydrolysis: Hydrodefluorination of PFC chain

Hydrolysis: Monophosphate ester to alcohol

Hydrolysis: Perfluorinated epoxide to beta keto carboxylic acid

Hydrolysis: Sulfonamide to sulfonic acid

Hydrolysis: Sulfonyl fluoride to sulfonic acid

Hydrolysis: Unsaturated fluorotelomer iodide to beta hydroxy fluorotelomer iodide-PTP

 

Hydroxylation Schemes

Hydroxylation: N-Alkyl sulfonamide to N-alkyl sulfonamide alcohol_PTP

Hydroxylation: Unsaturated fluorotelomer 2,4-dienoic acid to beta-hydroxy fluorotelomer acid

Hydroxylation: Unsaturated fluorotelomer acid to alpha hydroxy fluorotelomer acid

Hydroxylation: Unsaturated fluorotelomer acid to beta hydroxy fluorotelomer acid

 

 

N-Deacetylation/N-Dealkylation Schemes

N-Deacetylation: N-acetyl sulfonamide to sulfonamide  

N-Deacetylation: N-acetyl, N-alkyl sulfonamide to N-alkyl sulfonamide

N-Dealkylation: N-alkyl sulfonamide to sulfonamide

 

Oxidation Schemes

Oxidation: Alcohol to ketone

Oxidation: Alpha fluoro diol to acid fluoride and aldehyde with C-C bond cleavage_PTP

Oxidation: Alpha hydroxy fluorotelomer aldehyde to alpha hydroxy fluorotelomer carboxylic acid_PTP

Oxidation: Beta hydroxy fluorotelomer acid to beta keto fluorotelomer acid_PTP

Oxidation: Beta hydroxy gamma-delta unsaturated fluorotelomer acid to beta keto fluorotelomer acid_PTP

Oxidation: Beta oxidation of beta keto fluorotelomer acid_PTP

Oxidation: Beta oxidation of beta keto gamma-delta unsaturated fluorotelomer acid_PTP

Oxidation: Fluorotelomer alcohol to fluorotelomer aldehyde

Oxidation: Fluorotelomer alcohol to fluorotelomer carboxylic acid with loss of CF2 and methyl group

Oxidation: Fluorotelomer alcohol to fluorotelomer carboxylic acid with loss of methyl group

Oxidation: Fluorotelomer aldehyde to fluorotelomer carboxylic acid

Oxidation: Fluorotelomer carboxylic acid to 2,3-unsaturated fluorotelomer carboxylic acid

Oxidation: Fluorotelomer diol to alpha hydroxy fluorotelomer aldehyde_PTP

Oxidation: Fluorotelomer iodide to alpha beta unsaturated fluorotelomer iodide_PTP

Oxidation: Fluorotelomer polyethoxylate carboxylic acid to shortened fluorotelomer polyethoxylate_PTP

Oxidation: Fluorotelomer polyethoxylate to fluorotelomer polyethoxylate carboxylic acid_PTP

Oxidation: Fluorotelomer sulfone to fluorotelomer sulfonic acid and alkyl chain

Oxidation: Fluorotelomer sulfoxide to fluorotelomer sulfone

Oxidation: Fluorotelomer thioether to fluorotelomer sulfoxide

Oxidation: Hydrodefluorination with alpha oxidation

Oxidation: Hydrodefluorination with beta oxidation

Oxidation: N-Alkyl sulfonamide alcohol to N-alkyl sulfonamide carboxylic acid

Oxidation: Sulfinic acid to sulfonic acid

 

Reduction Schemes

Reduction: 2,3-Unsaturated fluorotelomer carboxylic acid to fluorotelomer carboxylic acid

Reduction: Beta fluoro unsaturated telomer acid to beta H unsaturated telomer acid

Reduction: Hydrogenolysis of chlorinated perfluorinated ether_PTP

Reduction: Methyl ketone to alcohol

Reduction: Sulfonamide to sulfinic acid

Reduction: Vicinal bis-defluorination of unsaturated carboxylic acid_PTP

 

Rank Assignment

 

Version History

 

The reaction schemes are written as generic reaction equations defining how a particular structural fragment will be modified by the transformation reaction.  These schemes are not balanced reactions showing all reactants and products (e.g., H2O, OH- and/or H+ are not shown as reactants in the schemes).  Additionally, the structural fragments in the reaction schemes are written with a minimal amount of specificity.  For example, the inclusion of hydrogen atoms in the scheme implies that there is a requirement for a hydrogen atom to present be in the specified position for the reactions to proceed; otherwise, it is assumed that, for simplicity, hydrogen atoms are not explicitly included. 

The schemes are encoded using the notation and structural query features from ChemAxon’s Marvin tools.  Definitions of some common symbols used in the reaction schemes are provided below:

·         L[a1;a2;…] is a list of possible atoms (a1, a2, …) that can occupy the position within the fragment

·         (A) is used to indicate an aliphatic carbon atom

·         (a) is used to indicate an aromatic carbon atom

·         (H1) indicates that the atom is bonded to one hydrogen

·         (H3) indicates that the atom is bonded to three hydrogens

·         (s*) indicates substituent count is as drawn for the atom

·         AH is used to represent any atom including hydrogen

Examples are provided for each reaction scheme in the library.  As is the case for the reaction schemes themselves, the example reactions do not show all of the reactants and products involved in the reduction reaction.  The example chemical is shown as the only reactant, and the products are the major transformation products reported in the study.  These example transformations from the peer-reviewed literature and government regulatory reports were used to test the reaction schemes in the library.

The schemes within the Anaerobic Biotransformation Reaction Library are ranked on a scale of one to seven according to their relative rate of transformation, with a higher rank indicating a faster transformation rate.   A database of measured rate constants or half-lives was compiled from a survey of peer-reviewed scientific literature and reports by government regulatory agencies to assign these ranks to each reaction scheme. 

 

 

Decarboxylation Schemes

Decarboxylation: Alpha carboxy ether to ether

SCHEME:

 

EXAMPLES:

·         Hexafluoropropylene oxide dimer acid (HFPO-DA; DTXSID70880215) (Liberatore et al., 2020)

 

Decarboxylation: Alpha hydroxy fluorotelomer carboxylic acid to fluorotelomer aldehyde

SCHEME:

 

EXAMPLES:

·         α-OH 5:3 FTCA (Wang et al., 2012)

 

 

Decarboxylation: Beta carboxy ketone to methyl ketone

SCHEME:

 

EXAMPLES:        

·         β-keto 7:3 FTCA (Washington et al., 2015)

 

 

 

Desulfonation Scheme

Desulfonation: Fluorotelomer sulfonate to fluorotelomer alcohol

SCHEME:

 

EXAMPLES:

·         6:2 fluorotelomer sulfonate (6:2 FTSA, DTXSID6067331; Zhang et al., 2016; Shaw et al., 2019; Van Hamme et al., 2013)

 

 

Epoxidation Scheme

Epoxidation: Alkene to epoxide_PTP

SCHEME:

This scheme includes an exclude rule to prevent epoxide formation at the carbon-carbon double bond adjacent to the carboxylic acid group in beta fluoro unsaturated telomer acids or the carbon-carbon double bond adjacent to the aldehyde group in beta fluoro unsaturated telomer aldehydes.

EXAMPLES:

·         2H,8H-2,8-PFUDoA (Arakaki et al., 2010) Note that this transformation is not included in the proposed biodegradation pathway shown in Figure 1; however, in the discussion section, Arakaki et al (2010) state “cleavage probably requires oxidative reactions such as epoxidation of the C=C double bond”.

 

 

Hydrolysis Schemes

Hydrolysis: Acid fluoride to carboxylic acid

SCHEME:

 

EXAMPLES:

·         Acetyl fluoride (DTXSID3060326) (Bunton and Fendler, 1966)

 

·         2,3,3,3-Tetrafluoropropanoyl fluoride (DTXSID20536674) (Koster et al, 1994)

 

Hydrolysis: Alpha difluoro alcohol to acid fluoride

SCHEME:

EXAMPLES:

·         1,1,2-trifluoropropan-1-ol (Koster et al., 1994)

 

Hydrolysis: Alpha fluoro secondary alcohol to ketone

SCHEME:

EXAMPLES:

·         1,2,2,3,3,4,4-heptafluorocyclobutanol (Andreades and England, 1961)

  

The product shown in brackets is hexafluorocyclobutanone hydrate, an intermediate proposed by Andreades and England (1961).  This molecule is a geminal diol which will be transformed to the carbonyl form shown as the final product.

 

Hydrolysis: Amide to carboxylic acid

SCHEME:

EXAMPLES:

·         Trifluoroacetamide (DTXSID1059868) (Meresaar and Bratt, 1974)

 

Hydrolysis: Beta hydroxy fluorotelomer iodide to diol_PTP

SCHEME:

EXAMPLES:

·       3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-1-iodooctan-2-ol (DTXSID70527451) (Ruan et al., 2013)

 

Hydrolysis: Carboxylic acid ester to carboxylic acid

SCHEME:

EXAMPLES:

·         8:2 Fluorotelomer methacrylate (8:2 FTMAc, DTXSID8062101) (Royer et al., 2015)

·         8:2 Fluorotelomer acrylate (8:2 FTAc, DTXSID5067348) (Royer et al., 2015)

·         8:2 Fluorotelomer stearate monoester (DTXSID601029611) (Dasu et al., 2012)

 

Hydrolysis: Diperfluorophosphinate to perfluorophosphonate

SCHEME:

 

 

EXAMPLES:

·         bis(nonafluorobutyl)phosphinic acid (DTXSID60556851) (Mahmood and Shreeve, 1986)

 

 

Hydrolysis: Diphosphate ester to monophosphate ester

SCHEME:

 

EXAMPLES:

·         6:2 Fluorotelomer phosphate diester (6:2 diPAP, DTXSID50561590) (Lee et al, 2014; Lewis et al, 2016)

 

Hydrolysis: Epoxide to diol_PTP

SCHEME:

EXAMPLES:

·         2H,8H-8,9-oxirane-PFUDoA (Arakaki et al., 2010).

Note that this transformation is not included in the proposed biodegradation pathway shown in Figure 1; however, in the discussion section, Arakaki et al (2010) state “…cleavage probably requires oxidative reactions such as epoxidation of the C=C double bond. Epoxidation and hydroxylation of unsaturated fatty acids by cytochrome P450 have been identified in various organisms.”.

 

Hydrolysis: Fluorotelomer acid to unsaturated telomer acid

SCHEME:

 

EXAMPLES:

·         2-(Perfluorooctyl) ethanoic acid (8:2 FTCA; DTXSID50451109) (Washington et al., 2015)

 

·         2-(Perfluorohexyl) ethanoic acid (6:2 FTCA; DTXSID50472556) (Ruan et al., 2014)

 

 

Hydrolysis: Fluorotelomer iodide to fluorotelomer alcohol

SCHEME:

 

EXAMPLES:

·         1H,1H,2H,2H-Perfluorooctyl iodide (6:2 Fluorotelomer iodide; DTXSID2047565) (Ruan et al., 2013)

 

 

Hydrolysis: Fluorotelomer urethane to fluorotelomer alcohol

SCHEME:

 

EXAMPLES:

·         Toluene-2,4-di(8:2fluorotelomerurethane) (Dasu and Lee, 2016)

 

·         Hexamethylene-1,6-di(8:2fluorotelomerurethane) (HMU) (Dasu and Lee, 2016)

 

 

Hydrolysis: Hydrodefluorination of PFC chain

SCHEME:

 

EXAMPLES:

·         2H,8H,8H-2-perfluorododecanoic acid (2H,8H,8H-2-PFUDoA) (Arakaki et al., 2017)

 


Hydrolysis: Monophosphate ester to alcohol

SCHEME:

 

EXAMPLES:

·         [(3,3,4,4,5,5,6,6,6‐Nonafluorohexyl)oxy]phosphonic acid (4:2 monoPAP; DTXSID901026573 )(Lee et al., 2010)

 

·         6:2 Fluorotelomer phosphate monoester (6:2 monoPAP; DTXSID90558000) (Lee et al., 2010)

 

·         3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-Heptadecafluorodecyl dihydrogen phosphate (8:2 monoPAP; DTXSID60874027) (Lee et al., 2010)

 

 

·         10:2 Fluorotelomer dihydrogen phosphate (10:2 monoPAP; DTXSID20206380) (Lee et al., 2010)

 

 

 

Hydrolysis: Perfluorinated epoxide to alpha keto carboxylic acid

SCHEME:

 

EXAMPLES:

·         Hexafluoropropylene oxide (HFPO, DTXSID6029177) (Kutsuna et al., 2018)

Kutsana (2018) shows the formation of numerous possible intermediates in the proposed reaction pathway for the hydrolysis of HFPO; however, the “Hydrolysis: Perfluorinated epoxide to alpha keto carboxylic acid” scheme is written to capture only the overall transformation of HFPO to the final product (3,3,3‐trifluoro‐2‐oxopropanoic acid).

 

Hydrolysis: Sulfonamide to sulfonic acid

SCHEME:

EXAMPLES:

·         Perfluorooctane sulfonamide (FOSA; DTXSID3038939) (Benskin et al, 2013)

 

Hydrolysis: Sulfonyl fluoride to sulfonic acid

SCHEME:

 

EXAMPLES:

·         2-acetamidobenzenesulfonyl fluoride (Aberlin and Bunton, 1970)

·         1,2,2,2-tetrafluoroethanesulfonyl fluoride (DTXSID50880177) (Knunyants and Sokolski, 1972)

 

·         1‐chloro‐1,2,2,2‐tetrafluoroethanesulfonyl fluoride (Knunyants and Sokolski, 1972)

 

Hydrolysis: Unsaturated fluorotelomer iodide to beta hydroxy fluorotelomer iodide-PTP

SCHEME:

EXAMPLES:

·         (1Z)-3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-1-iodooct-1-ene) (Ruan et al., 2013)

 

 

Hydroxylation Schemes

Hydroxylation: N-Alkyl sulfonamide to N-alkyl sulfonamide alcohol_PTP

SCHEME:

 

EXAMPLES:

·         N-ethyl-perfluorooctanesulfonamide (N-EtFOSA; DTXSID1032646) (Benskin et al., 2013)

 

 

Hydroxylation: Unsaturated fluorotelomer 2,4-dienoic acid to beta-hydroxy fluorotelomer acid

SCHEME:

EXAMPLES:

·         7:3 FTUUCA (Washington et al., 2015)

 

Hydroxylation: Unsaturated fluorotelomer acid to alpha hydroxy fluorotelomer acid

SCHEME:

 

EXAMPLES:

·         5:3 Fluorotelomer unsaturated carboxylic acid (5:3 FTUCA) (Wang et al., 2012)

  

 

Hydroxylation: Unsaturated fluorotelomer acid to beta hydroxy fluorotelomer acid

SCHEME:

 

EXAMPLES:

·         7:3 Fluorotelomer unsaturated carboxylic acid (7:3 FTUCA; DTXSID30822919) (Wang et al., 2009)

 

 

N-Deacetylation/N-Dealkylation Schemes

N-Deacetylation: N-acetyl sulfonamide to sulfonamide 

SCHEME:

 

EXAMPLES:

·         2(perfluorooctanesulfonamido)acetic acid (FOSAA; DTXSID40440941) (Rhoads et al., 2008)

 

N-Deacetylation: N-acetyl, N-alkyl sulfonamide to N-alkyl sulfonamide

SCHEME:

 

EXAMPLES:

·         N-ethyl perfluorooctane sulfonamido acetate (N-EtFOSAA; DTXSID5062760) (Benskin et al., 2013; Rhoads et al., 2008)

 

 

N-Dealkylation: N-alkyl sulfonamide to sulfonamide

SCHEME:

 

EXAMPLES:

·         N-ethyl-perfluorooctanesulfonamide (N-EtFOSA; DTXSID1032646) (Rhoads et al., 2008)

 

 

Oxidation Schemes

Oxidation: Alcohol to ketone

SCHEME:

 

EXAMPLES:

·         3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-Pentadecafluorononan-2-ol (7:2 sFTOH; DTXSID10517598) (Wang et al., 2009; Washington et al., 2015)

 

 

 

Oxidation: Alpha fluoro diol to acid fluoride and aldehyde with C-C bond cleavage_PTP

SCHEME:

 

EXAMPLES:

·         1,1,1,2,2,4,5,5,6,6,7,7,7-tridecafluoroheptane-3,4-diol (Arakaki et al., 2010)

 

 

Oxidation: Alpha hydroxy fluorotelomer aldehyde to alpha hydroxy fluorotelomer carboxylic acid_PTP

SCHEME:

 

EXAMPLES:

·         3-Hydroxy-4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-pentadecafluorodecanoic acid (Washington et al., 2015)

 

 

Oxidation: Beta hydroxy fluorotelomer acid to beta keto fluorotelomer acid_PTP

SCHEME:

EXAMPLES:

·         3-Hydroxy-4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-pentadecafluorodecanoic acid (Washington et al., 2015)

 

 

Oxidation: Beta hydroxy gamma-delta unsaturated fluorotelomer acid to beta keto fluorotelomer acid_PTP

SCHEME:

EXAMPLES:

·         β-OH 7:3 FTUCA (Washington et al., 2015)

 

Oxidation: Beta oxidation of beta keto fluorotelomer acid_PTP

SCHEME:

EXAMPLES:

·         3-Oxo-4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-pentadecafluorodecanoic acid (Washington et al., 2015)

 

 

Oxidation: Beta oxidation of beta keto gamma-delta unsaturated fluorotelomer acid_PTP

SCHEME:

EXAMPLES:

·         β-Keto 7:3 FTUCA (Washington et al., 2015)

 

 

Oxidation: Fluorotelomer alcohol to fluorotelomer aldehyde

SCHEME:

EXAMPLES:

·         3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctan-1-ol (6:2 FTOH; DTXSID5044572) (Zhao et al., 2013)

·         1,1,2,2-Tetrahydroperfluoro-1-decanol (8:2 FTOH; DTXSID7029904) (Wang et al., 2009)

 

Oxidation: Fluorotelomer alcohol to fluorotelomer carboxylic acid with loss of CF2 and methyl group

SCHEME:


EXAMPLES:

·         1H,1H,1H,2H-Perfluoro-2-heptanol (5:2 sFTOH; DTXSID80597206) (Zhao et al., 2013; Hamid et al., 2020)

 

 

Oxidation: Fluorotelomer alcohol to fluorotelomer carboxylic acid with loss of methyl group

SCHEME:

 

EXAMPLES:

·         1H,1H,1H,2H-Perfluoro-2-heptanol (5:2 sFTOH; DTXSID80597206) (Zhao et al., 2013)

 

 

Oxidation: Fluorotelomer aldehyde to fluorotelomer carboxylic acid

SCHEME:

 

EXAMPLES:

·         3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctanal (6:2 FTAL; DTXSID20895379) (Zhang et al., 2013)

 

 

·         3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-Heptadecafluorod (8:2 FTAL; DTXSID10895489) (Martin et al., 2005)

 

 

Oxidation: Fluorotelomer carboxylic acid to 2,3-unsaturated fluorotelomer carboxylic acid

SCHEME:

 

EXAMPLES:

·         2H,2H,3H,3H-Perfluorooctanoic acid (5:3 FTCA; DTXSID20874028) (Wang et al., 2012)

 

 

Oxidation: Fluorotelomer diol to alpha hydroxy fluorotelomer aldehyde_PTP

SCHEME:

 

EXAMPLES:

·         3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctane-1,2-diol (Ruan et al., 2013)

 

 

Oxidation: Fluorotelomer iodide to alpha beta unsaturated fluorotelomer iodide_PTP

SCHEME:

EXAMPLES:

·         1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluoro-8-iodooctane (DTXSID2047565) (Ruan et al., 2013)

 

Oxidation: Fluorotelomer polyethoxylate carboxylic acid to shortened fluorotelomer polyethoxylate_PTP

SCHEME:

 

EXAMPLES:

·         30,30,31,31,32,32,33,33,34,34,35,35,35-tridecafluoro-3,6,9,12,15,18,21,24,27-nonaoxapentatriacontanoic acid (Frömel and Knepper, 2010)

 

 

Oxidation: Fluorotelomer polyethoxylate to fluorotelomer polyethoxylate carboxylic acid_PTP

SCHEME:

 

EXAMPLES:

·         6:2 FTEO9 (Frömel and Knepper, 2010)

 

Oxidation: Fluorotelomer sulfone to fluorotelomer sulfonic acid and alkyl chain

SCHEME:

EXAMPLES:

·         6:2 FtSO2AoS (DTXSID90894132) (Harding-Majanovic et al., 2015)

 

Oxidation: Fluorotelomer sulfoxide to fluorotelomer sulfone

SCHEME:

EXAMPLES:

·         4:2 FtSOAoS (Harding-Majanovic et al., 2015)

 

·         6:2 FtSOAoS (DTXSID90892592) (Harding-Majanovic et al., 2015)

 

·         8:2 FtSOAoS (Hardin-Majanovic et al., 2015)

 

 

Oxidation: Fluorotelomer thioether to fluorotelomer sulfoxide

SCHEME:

EXAMPLES:

·         4:2 Fluorotelomer thioether amido sulfonic acid (4:2 FtTAoS; DTXSID00892528) (Harding-Majanovic et al., 2015)

 

·         6:2 Fluorotelomer thia propanoamido dimethyl ethyl sulfonate (6:2 FtTAoS; DTXSID90892330) (Harding-Majanovic et al., 2015)

·         8:2 Fluorotelomer thioether amido sulfonic acid (8:2 FtTAoS; DTXSID30892334) (Hardin-Majanovic et al., 2015)

 

 

Oxidation: Hydrodefluorination with alpha oxidation

SCHEME:

 

EXAMPLES:

·         7:2 Fluorotelomer ketone (Wang et al., 2009; Washington et al., 2015)

 

 

 

Oxidation: Hydrodefluorination with beta oxidation

SCHEME:

 

EXAMPLES:

·         2,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooct-2-enoic acid (Washington et al., 2015)

 

Oxidation: N-Alkyl sulfonamide alcohol to N-alkyl sulfonamide carboxylic acid

SCHEME:

 

EXAMPLES:

·         2-(N-(Perfluorobutylsulfonyl)-N-methylamino) ethanol (MeFBSE; DTXSID0067848 (Lange et al., 2018)

 

·         2-Perfluorooctylsulfonyl-N-ethylaminoethyl alcohol (N-EtFOSE; DTXSID6027426) (Lange et al., 2018; Benskin et al., 2013; Rhoads et al., 2008)

 

 

 

Oxidation: Sulfinic acid to sulfonic acid

SCHEME:

 

EXAMPLES:

·         1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-Heptadecafluorooctane-1-sulfinic Acid (PFOSI; DTXSID10904262) (Rhoads et al., 2008)

 

 

Reduction Schemes

Reduction: 2,3-Unsaturated fluorotelomer carboxylic acid to fluorotelomer carboxylic acid

SCHEME:

 

EXAMPLES:

·         2-Decenoic acid, 4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-pentadecafluoro- (7:3 FTUCA; DTXSID30822919) (Washington et al., 2015)

·         4,4,5,5,6,6,6-Heptafluorohex-2-enoic acid (4:3 FTUCA; DTXSID30895360) (Wang et al., 2012; Martin et al., 2005)

 

Reduction: Beta fluoro unsaturated telomer acid to beta H unsaturated telomer acid

SCHEME:

 

EXAMPLES:

·         8:2 Fluorotelomer unsaturated carboxylic acid (8:2 FTUCA; DTXSID60825615) (Zhang et al., 2016; Fasano et al., 2006)

·         5:2 Fluorotelomer unsaturated carboxylic acid (5:2 FTUCA; DTXSID201036278) (Wang et al., 2012)

 

 

Reduction: Hydrogenolysis of chlorinated perfluorinated ether_PTP

SCHEME:

 

EXAMPLES:

·         Chlorinated perfluorinated ether (Washington et al., 2015)

 

 

Reduction: Methyl ketone to alcohol

SCHEME:

 

EXAMPLES:

·         Methyl heptafluoropropyl ketone (5:2 Ketone) (Wang et al., 2012)

 

·         Methyl Pentadecafluoroheptyl Ketone (7:2 Ketone) (Washington et al., 2015)

 

 

Reduction: Sulfonamide to sulfinic acid

SCHEME:

 

EXAMPLES:

·         2-(N-Ethylperfluorooctanesulfonamido) acetic acid (N-EtFOSAA; DTXSID5062760) (Boulanger et al., 2005)

 

 

 

Reduction: Vicinal bis-defluorination of unsaturated carboxylic acid_PTP

SCHEME:

 

EXAMPLES:

·         7:3 Fluorotelomer unsaturated carboxylic acid (7:3 FTUCA, DTXSID30822919) (Washington et al., 2015)

 

 

Rank Assignment

Rank Levels

Rank

 

Upper Limit (days)

 

Upper Limit in Other Units

 

7

0.020833333

30 minutes

6

0.138888889

200 minutes

5

1

1 day

4

7

1 week

3

60

2 months

2

365

1 year

1

3650

10 years

 

 

 

 

Rank of Individual Reaction Schemes

#

Reaction Scheme Name

Rank

 

Decarboxylation

 

1

Decarboxylation: Alpha carboxy ether to ether

1

2

Decarboxylation: Alpha hydroxy fluorotelomer carboxylic acid to fluorotelomer aldehyde

5

3

Decarboxylation: Beta carboxy ketone to methyl ketone

3

 

Desulfonation

 

4

Desulfonation: Fluorotelomer sulfonate to fluorotelomer alcohol

4

 

Epoxidation

 

5

Epoxidation: Alkene to epoxide_PTP

4

 

Hydrolysis

 

6

Hydrolysis: Acid fluoride to carboxylic acid

7

7

Hydrolysis: Alpha difluoro alcohol to acid fluoride

7

8

Hydrolysis: Alpha fluoro secondary alcohol to ketone

7

9

Hydrolysis: Amide to carboxylic acid

4

10

Hydrolysis: Beta hydroxy fluorotelomer Iodide to diol_PTP

3

11

Hydrolysis: Carboxylic acid ester to carboxylic acid

3

12

Hydrolysis: Diperfluorophosphinate to perfluorophosphonate

1

13

Hydrolysis: Diphosphate ester to monophosphate ester

2

14

Hydrolysis: Epoxide to diol_PTP

5

15

Hydrolysis: Fluorotelomer acid to unsaturated telomer acid

4

16

Hydrolysis: Fluorotelomer iodide to fluorotelomer alcohol

3

17

Hydrolysis: Fluorotelomer urethane to fluorotelomer alcohol

2

18

Hydrolysis: Hydrodefluorination of PFC chain

3

19

Hydrolysis: Monophosphate ester to alcohol

3

20

Hydrolysis: Perfluorinated epoxide to alpha keto carboxylic acid

7

21

Hydrolysis: Sulfonamide to sulfonate

3

22

Hydrolysis: Sulfonyl fluoride to sulfonate

3

23

Hydrolysis: Unsaturated fluorotelomer iodide to beta hydroxy fluorotelomer iodide-PTP

3

 

Hydroxylation

 

24

Hydroxylation: N-Alkyl sulfonamide to N-alkyl sulfonamide alcohol_PTP

3

25

Hydroxylation: Unsaturated fluorotelomer 2,4-dienoic acid to beta-hydroxy fluorotelomer acid

3

26

Hydroxylation: Unsaturated fluorotelomer acid to alpha hydroxy fluorotelomer acid

4

27

Hydroxylation: Unsaturated fluorotelomer acid to beta hydroxy fluorotelomer acid

3

 

N-Deacetylation/N-Dealkylation

 

28

N-Deacetylation: N-acetyl sulfonamide to sulfonamide 

4

29

N-Deacetylation: N-acetyl, N-alkyl sulfonamide to N-alkyl sulfonamide

3

30

N-Dealkylation: N-alkyl sulfonamide to sulfonamide

3

 

Oxidation

 

31

Oxidation: Alcohol to ketone

3

32

Oxidation: Alpha fluoro diol to acid fluoride and aldehyde with C-C bond cleavage_PTP

3

33

Oxidation: Alpha hydroxy fluorotelomer aldehyde to alpha hydroxy fluorotelomer carboxylic acid_PTP

3

34

Oxidation: Beta hydroxy fluorotelomer acid to beta keto fluorotelomer acid_PTP

3

35

Oxidation:  Beta hydroxy gamma-delta unsaturated fluorotelomer acid to beta keto fluorotelomer acid_PTP

3

36

Oxidation: Beta oxidation of beta keto fluorotelomer acid

3

37

Oxidation: Beta oxidation of beta keto gamma-delta unsaturated fluorotelomer acid_PTP

3

38

Oxidation: Fluorotelomer alcohol to fluorotelomer aldehyde

4

39

Oxidation: Fluorotelomer alcohol to fluorotelomer carboxylic acid with loss of CF2 and methyl groups

3

40

Oxidation: Fluorotelomer alcohol to fluorotelomer carboxylic acid with loss of methyl group

2

41

Oxidation: Fluorotelomer aldehyde to fluorotelomer carboxylic acid

6

42

Oxidation: Fluorotelomer carboxylic acid to 2,3-unsaturated fluorotelomer carboxylic acid

2

43

Oxidation: Fluorotelomer diol to alpha hydroxy fluorotelomer aldehyde_PTP

3

44

Oxidation: Fluorotelomer iodide to alpha beta unsaturated fluorotelomer iodide_PTP

3

45

Oxidation: Fluorotelomer polyethoxylate carboxylic acid to shortened fluorotelomer polyethoxylate_PTP

4

46

Oxidation: Fluorotelomer polyethoxylate to fluorotelomer polyethoxylate carboxylic acid_PTP

4

47

Oxidation: Fluorotelomer sulfone to fluorotelomer sulfonic acid and alkyl chain

3

48

Oxidation: Fluorotelomer sulfoxide to fluorotelomer sulfone

3

49

Oxidation: Fluorotelomer thioether to fluorotelomer sulfoxide

4

50

Oxidation: Hydrodefluorination with alpha oxidation

3

51

Oxidation: Hydrodefluorination with beta oxidation

4

52

Oxidation: N-Alkyl sulfonamide alcohol to N-alkyl sulfonamide carboxylic acid

3

53

Oxidation: Sulfinic acid to sulfonic acid

5

 

Reduction

 

54

Reduction: 2,3-Unsaturated fluorotelomer carboxylic acid to fluorotelomer carboxylic acid

3

55

Reduction: Beta fluoro unsaturated telomer acid to beta H unsaturated telomer acid

3

56

Reduction: Hydrogenolysis of chlorinated perfluorinated ether_PTP

3

57

Reduction: Methyl ketone to alcohol

3

58

Reduction: Sulfonamide to sulfinic acid

3

59

Reduction: Vicinal bis-defluorination of unsaturated carboxylic acid_PTP

3

 

 

Version History

The development of version 1.0 of the CTS PFAS Environmental Reaction Library was described in detail in the following publication:

E.J. Weber, C. Tebes-Stevens, J.W. Washington. 2022. Development of a PFAS reaction library: identifying plausible transformation pathways in environmental and biological systems. Environmental Science: Processes & Impacts, 24, pp. 689–753.

Version 1.1 includes revisions to various reaction schemes and the addition of the following reaction schemes:

·         Hydrolysis: Unsaturated fluorotelomer iodide to beta hydroxy fluorotelomer iodide-PTP

·         Hydroxylation: Unsaturated fluorotelomer 2,4-dienoic acid to beta-hydroxy fluorotelomer acid

·         Oxidation: Beta hydroxy gamma-delta unsaturated fluorotelomer acid to beta keto fluorotelomer acid_PTP

·         Oxidation: Beta oxidation of beta keto gamma-delta unsaturated fluorotelomer acid_PTP

·         Oxidation: Fluorotelomer polyethoxylate carboxylic acid to shortened fluorotelomer polyethoxylate_PTP

·         Oxidation: Hydrodefluorination with beta oxidation

Three schemes from the version 1.0 library were deleted, because they are covered by other schemes in the version 1.1 library:

·         Hydrolysis: Alpha fluoro primary alcohol to aldehyde

·         Hydrolysis: Alpha hydroxy iodide to diol-PTP

·         Oxidation: Alpha oxidation of alpha hydroxy fluorotelomer carboxylic acid to fluorotelomer aldehyde

 

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