Dimroth and Reichardt ET

Dimroth and Reichardt determined the wave length of the absorption maximum for a betain dye as a measure of the ionizing power of solvents.
Molecular structure of Reichardt′s dye The wave length is converted to kcal/mol (=2.86x104λ-1) to give ET(30). The dye is popular because the changes in wave length are in the visible spectrum (see below). However, it is poorly soluble at the ends of the ET scale and may be protonated.
ET is mainly a measure of hydrogen bond donation (HBD) and is strongly correlated with →Kamlet and Taft's α, →Gutmann's acceptor number (AN), →Swain's acity (A), →Fawcett's acidity (Ap) and →Catalán's SA.
See → α vs ET and → AN vs ET et c.
Normalizing to a scale from TMS (0.00) to water (1.00) gives ETN which is a range more in line with other solvent polarity scales.

Note: Colours shown here are very approximate - in particular at the low and high ends of the scale. Click →here to sort by ET/colour.

See e.g. →IUPAC Gold Book, →Reichardt's dye, →"Solvatochromic Dyes as Solvent Polarity Indicators" (article), →"Lösungsmittel-Effekte in der organischen Chemie" (book), →"Solvents and solvent effects in organic chemistry" (book)

NameFormulaETETNcolour
dimethyl sulfideC2H6S26.8-0.12
tetramethylsilaneC4H12Si30.70.00
cyclohexaneC6H1230.90.01
2-methylbutaneC5H1230.90.01
hexaneC6H1431.00.01
nonaneC9H2031.00.01
decaneC10H2231.00.01
pentaneC5H1231.10.01
heptaneC7H1631.10.01
dodecaneC12H2631.10.01
octaneC8H1831.10.01
cis-decalinC10H1831.20.02
tetrachloroetheneC2Cl431.90.04
triethylamineC6H15N32.10.04
tributylamineC12H27N32.10.04
cyclohexeneC6H1032.20.05
hexachloro-1,3-butadieneC4Cl632.20.05
1-hexeneC6H1232.40.05
tetrachloromethaneCCl432.40.05
hexachlorocyclopentadieneC5Cl632.80.06
hexachloropropeneC3Cl632.80.06
carbon disulfideCS232.80.06
1,3,5-trimethylbenzeneC9H1232.90.07
dibutyl etherC8H18O33.00.07
1,2,3,4-tetramethylbenzeneC10H1433.00.07
1,4-dimethylbenzeneC8H1033.10.07
1,1,2-trichloro-1,2,2-trifluoroethaneC2Cl3F333.20.08
1,3,5-trifluorobenzeneC6H3F333.20.08
1,3-dimethylbenzeneC8H1033.30.08
trichlorofluoromethaneCCl3F33.30.08
1,2-dichloro-1,2,3,3,4,4-hexafluorocyclobutaneC4Cl2F633.30.08
tetrahydronaphthaleneC10H1233.50.09
1,2-dichloro-1,1,2,3,3,3-hexafluoropropaneC3Cl2F633.60.09
1,1,1-trichlorotrifluoroethaneC2Cl3F333.80.10
1,1-diethoxymethaneC5H12O233.90.10
tolueneC7H833.90.10
diisopropyl etherC6H14O34.00.10
1,3,3-trimethyl-2-oxabicyclo[2.2.2]octaneC10H18O34.00.10
dipropyl etherC6H14O34.00.10
2,6-di-tert-butylpyridineC13H21N34.00.10
hexafluorobenzeneC6F634.20.11
cyclohexylbenzeneC12H1634.20.11
trans-1,2-dichloroetheneC2H2Cl234.20.11
benzeneC6H634.30.11
1-hexyneC6H1034.30.11
2-methyl-2-methoxybutaneC6H14O34.40.11
carbon dioxideCO234.50.12
diethyl etherC4H10O34.50.12
1,4-dibromo-2-methylbenzeneC7H6Br234.70.12
2-methoxy-2-methylpropaneC5H12O34.70.12
styreneC8H834.80.13
bromotrichloromethaneCBrCl334.80.13
1-iodobutaneC4H9I34.90.13
diisopropyl sulfideC6H14S34.90.13
di-n-butyl sulfideC8H18S34.90.13
1-methylnaphthaleneC11H1035.30.14
diethylamineC4H11N35.40.15
thiopheneC4H4S35.40.15
3-methyltetrahydropyranC6H12O35.50.15
piperidineC5H11N35.50.15
diphenyl etherC12H10O35.50.15
diethyl sulfideC4H10S35.70.15
dimethoxymethaneC3H8O235.80.16
trichloroetheneC2HCl335.90.16
thianeC5H10S35.90.16
furanC4H4O36.00.16
dioxaneC4H8O236.00.16
ethoxyetheneC4H8O36.20.17
1,1,1-trichloroethaneC2H3Cl336.20.17
iodobenzeneC6H5I36.20.17
chlorocyclohexaneC6H11Cl36.20.17
1,2,4-trichlorobenzeneC6H3Cl336.20.17
dibenzyl etherC14H14O36.30.17
pentafluoropyridineC5F5N36.30.17
2,4,6-trimethylpyridineC8H11N36.40.18
pentachloroethaneC2HCl536.40.18
1,4-difluorobenzeneC6H4F236.40.18
N,N-dimethylanilineC8H11N36.50.18
1,3-dibromobenzeneC6H4Br236.50.18
2-methyl-2-propanamineC4H11N36.50.18
diiodomethaneCH2I236.50.18
2-methyltetrahydrofuranC5H10O36.50.18
ethoxybenzeneC8H10O36.60.18
bromobenzeneC6H5Br36.60.18
1-bromobutaneC4H9Br36.60.18
oxaneC5H10O36.60.18
1,10-dichlorodecaneC10H20Cl236.60.18
thiolaneC4H8S36.70.19
1,3-dichlorobenzeneC6H4Cl236.70.19
chlorobenzeneC6H5Cl36.80.19
2,6-dimethylpyridineC7H9N36.90.19
1-chlorobutaneC4H9Cl36.90.19
1-iodonaphthaleneC10H7I36.90.19
1,1-dichloroetheneC2H2Cl237.00.19
methylsulfanylbenzeneC7H8S37.00.19
1-chloronaphthaleneC10H7Cl37.00.19
diethyl carbonateC5H10O337.00.19
fluorobenzeneC6H5F37.00.19
methoxybenzeneC7H8O37.10.20
ethynylbenzeneC8H637.20.20
N,N-dimethylcyclohexylamineC8H17N37.30.20
1,3-difluorobenzeneC6H4F237.30.20
tetrahydrofuranC4H8O37.40.21
1-chloropropaneC3H7Cl37.40.21
3,6,9-trioxaundecaneC8H18O337.50.21
propyl acetateC5H10O237.50.21
5-nonanoneC9H18O37.50.21
1,2-dibromobenzeneC6H4Br237.60.21
bromoethaneC2H5Br37.60.21
butylamineC4H11N37.60.21
tribromomethaneCHBr337.70.22
2,2-dichloropropaneC3H6Cl237.90.22
methyl 2-methyl-2-propenoateC5H8O237.90.22
2,4-dimethyl-3-ethyl-3-pentanolC9H20O37.90.22
vinyl acetateC4H6O238.00.23
methyl propanoateC4H8O238.00.23
2,6-dimethyl-4-heptanoneC9H18O38.00.23
1,2-dichlorobenzeneC6H4Cl238.00.23
ethyl acetateC4H8O238.10.23
methyl benzoateC8H8O238.10.23
ethyl benzoateC9H10O238.10.23
1,2-dimethoxyethaneC4H10O238.20.23
2-methylpyridineC6H7N38.30.23
1,2-dibromoethaneC2H4Br238.30.23
pentafluorobenzeneC6HF538.40.24
1,2-dimethoxybenzeneC8H10O238.40.24
3-ethyl-3-pentanolC7H16O38.50.24
butyl acetateC6H12O238.50.24
trifluoromethylbenzeneC7H5F338.50.24
bis(2-methoxyethyl) etherC6H14O338.60.24
2,4-dimethyl-3-pentanoneC7H14O38.70.25
ethyl trichloroacetateC4H5Cl3O238.70.25
methyl 2-propenoateC4H6O238.80.25
dimethyl carbonateC3H6O338.80.25
3,4-dimethylpyridineC7H9N38.90.25
4-heptanoneC7H14O38.90.25
2,5,8,11-tetraoxadodecaneC8H18O438.90.25
3,3-dimethyl-2-butanoneC6H12O39.00.26
trichloromethaneCHCl339.10.26
pyrrolidineC4H9N39.10.26
1,2-dibromopropaneC3H6Br239.10.26
3-pentanoneC5H10O39.30.27
1,2-difluorobenzeneC6H4F239.30.27
1,1,3,3-tetramethylguanidineC5H13N339.30.27
1,1-dichloroethaneC2H4Cl239.40.27
quinolineC9H7N39.40.27
dibromomethaneCH2Br239.40.27
ethyl chloroacetateC4H7ClO239.40.27
4-methyl-2-pentanoneC6H12O39.40.27
1,1,2,2-tetrachloroethaneC2H2Cl439.40.27
cyclopentanoneC5H8O39.40.27
dibutyl phthalateC16H22O439.50.27
hexamethylphosphorothioic acid triamideC6H18N3PS39.50.27
1,4-dichlorobutaneC4H8Cl239.50.27
nitrocyclohexaneC6H11NO239.60.27
methyl trichloroacetateC3H3Cl3O239.60.27
tributyl phosphateC12H27O4P39.60.27
4-methylpyridineC6H7N39.60.27
3-bromopyridineC5H4BrN39.70.28
cyclohexanoneC6H10O39.80.28
methyloxiraneC3H6O39.80.28
methyl acetateC3H6O240.00.29
trichloroethanenitrileC2Cl3N40.00.29
2-hexanoneC6H12O40.10.29
2,4-dimethyl-3-pentanolC7H16O40.10.29
1,3-dichloropropaneC3H6Cl240.20.29
1,1,2-trichloroethaneC2H3Cl340.30.30
1-cyclohexyl-2-pyrrolidoneC10H17NO40.40.30
triacetinC9H14O640.40.30
1,2,3-trichloropropaneC3H5Cl340.40.30
tripropyl phosphateC9H21O4P40.50.30
pyridineC5H5N40.50.30
acetophenoneC8H8O40.60.31
dichloromethaneCH2Cl240.70.31
dimethyl phthalateC10H10O440.70.31
3-chloro-1,1,1-trifluoropropaneC3H4ClF340.70.31
N-methylformanilideC8H9NO40.80.31
hexamethylphosphoramideC6H18N3OP40.90.31
3-methyl-2-butanoneC5H10O40.90.31
ethyl formateC3H6O240.90.31
N,N,N',N'-tetraethylsulfamideC8H20N2O2S41.00.32
N,N,N',N'-tetramethylureaC5H12N2O41.00.32
morpholineC4H9NO41.00.32
2-methyl-2-butanolC5H12O41.10.32
2-heptanoneC7H14O41.10.32
2-pentanoneC5H10O41.10.32
nitrobenzeneC6H5NO241.20.32
1,2-dichloroethaneC2H4Cl241.30.33
2-bromopyridineC5H4BrN41.30.33
2-butanoneC4H8O41.30.33
5-acetyl-5-methyl-1,3-dioxaneC7H12O341.50.33
benzonitrileC7H5N41.50.33
1-methylazepan-2-oneC7H13NO41.60.34
bis(2-chloroethyl) etherC4H8Cl2O41.60.34
1-ethyl-2-pyrrolidoneC6H11NO41.60.34
triethyl phosphateC6H15O4P41.70.34
2,6-di-tert-butylphenolC14H22O41.80.34
2,6-dimethoxyphenolC8H10O341.80.34
N,N-diethylformamideC5H11NO41.80.34
2-chloropyridineC5H4ClN41.90.35
cis-1,2-dichloroetheneC2H2Cl241.90.35
phenyl 2-hydroxybenzoateC13H10O341.90.35
2,6-di-tert-butyl-4-methylphenolC15H24O41.90.35
1,2-diaminoethaneC2H8N242.00.35
N,N-diisopropylcyanamideC7H14N242.00.35
piperidine-1-carbonitrileC6H10N242.10.35
1,3-dimethyltetrahydropyrimidin-2(1H)-oneC6H12N2O42.10.35
N-methylpyrrolidoneC5H9NO42.20.35
2-propanoneC3H6O42.20.35
methylphosphonic acid bis(dimethylamide)C5H15N2OP42.30.36
tri-n-butyl-n-dodecylphosphonium iodideC24H52IP42.30.36
2-fluoropyridineC5H4FN42.40.36
N,N-diethylacetamideC6H13NO42.40.36
1,3-dimethyl-2-imidazolidinoneC5H10N2O42.50.36
N-methylanilineC7H9N42.50.36
pyrrolidine-1-carbonitrileC5H8N242.60.37
tri-n-butyl-n-dodecylphosphonium chlorideC24H52ClP42.60.37
2-phenylacetonitrileC8H7N42.70.37
morpholine-4-carbonitrileC5H8N2O42.80.37
1-methylpyrrolidin-2-thioneC5H9NS42.80.37
2,3,6-trimethylphenolC9H12O42.90.38
3-methylsulfolaneC5H10O2S43.00.38
tetrabutylphosphonium chlorideC16H36ClP43.00.38
1,3-dioxolaneC3H6O243.10.38
butanenitrileC4H7N43.10.38
isopropyl nitrateC3H7NO343.10.38
tetrabutylammonium bromideC16H36BrN43.30.39
N,N-diethylcyanamideC5H10N243.30.39
2,6-difluoropyridineC5H3F2N43.30.39
tetra-n-butylphosphonium bromideC16H36BrP43.50.40
thiolane-1-oxideC4H8OS43.60.40
propanenitrileC3H5N43.60.40
trimethyl phosphateC3H9O4P43.60.40
nitroethaneC2H5NO243.60.40
2-methyl-2-propanolC4H10O43.70.40
N,N-dimethylacetamideC4H9NO43.70.40
N,N-dimethylformamideC3H7NO43.80.40
dimethylcyanamideC3H6N243.80.40
tetra-n-hexylammonium benzoateC31H57NO243.90.41
acetic anhydrideC4H6O343.90.41
sulfolaneC4H8O2S44.00.41
N,N-dimethylthioformamideC3H7NS44.00.41
methyl methylthiomethyl sulfoxideC3H8OS244.00.41
2-cyanopyridineC6H4N244.20.42
anilineC6H7N44.30.42
oxolan-2-oneC4H6O244.30.42
2-nitrophenolC6H5NO344.40.42
3-methoxypropanenitrileC4H7NO44.40.42
1-chloro-2,3-epoxypropaneC3H5ClO44.50.43
tri-n-butyl-n-dodecylphosphonium bromideC24H52BrP44.50.43
2-methoxy-1,3-dioxolaneC4H8O344.50.43
3-methyloxazolidin-2-oneC4H7NO244.90.44
methyl formateC2H4O245.00.44
dimethyl sulfoxideC2H6OS45.10.44
2,3-dimethylphenolC8H10O45.10.44
methyl 2-hydroxybenzoateC8H8O345.40.45
4-methoxyphenolC7H8O245.40.45
tetra-n-propylammonium 2-hydroxy-4-morpholinepropanesulfonateC19H42N2O5S45.50.46
2-chloroanilineC6H6ClN45.50.46
acetonitrileC2H3N45.60.46
3-pentanolC5H12O45.70.46
3-methyl-2-butanolC5H12O45.70.46
2,3,5-trimethylphenolC9H12O45.80.47
1,1,1-trichloroacetoneC3H3Cl3O45.90.47
2,4-di-tert-butylphenolC14H22O46.20.48
2,6-dichlorophenolC6H4Cl2O46.30.48
nitromethaneCH3NO246.30.48
chloroacetonitrileC2H2ClN46.40.48
2-pentanolC5H12O46.50.49
4-methyl-2-oxo-1,3-dioxolaneC4H6O346.60.49
1-phenylethanolC8H10O46.70.49
2-propenenitrileC3H3N46.70.49
2-tert-butyl-4-methylphenolC11H16O46.80.50
cyclohexanolC6H12O46.90.50
cyclopentanolC5H10O47.00.50
2-butanolC4H10O47.10.51
3-aminophenolC6H7NO47.10.51
2-aminophenolC6H7NO47.20.51
3,4-dimethylphenolC8H10O47.20.51
3,5-dimethylphenolC8H10O47.50.52
1-dodecanolC12H26O47.50.52
undecanolC11H24O47.60.52
decanolC10H22O47.70.52
nonanolC9H20O47.80.53
2-methyl-1-butanolC5H12O48.00.53
octanolC8H18O48.30.54
2-pyrrolidoneC4H7NO48.30.54
3-hydroxy-4-isopropyltolueneC10H14O48.40.55
3-phenylpropanolC9H12O48.50.55
heptanolC7H16O48.50.55
2-methyl-1-propanolC4H10O48.60.55
1-methoxy-2-propanolC4H10O248.60.55
1,3-dioxolan-2-oneC3H4O348.60.55
5-isopropyl-2-methylphenolC10H14O48.70.56
hexanolC6H14O48.80.56
3-methyl-1-butanolC5H12O49.00.56
pentanolC5H12O49.10.57
3-methylsydnoneC3H4N2O249.20.57
2,4-pentanedioneC5H8O249.20.57
2-propanolC3H8O49.20.57
2-tert-butylphenolC10H14O49.20.57
ethyl 3-oxobutanoateC6H10O349.40.58
2-phenylethanolC8H10O49.50.58
tert-butylhydroperoxideC4H10O249.70.59
2-butoxyethanolC6H14O250.00.60
3-n-propyl-1,2,3-oxadiazolium-5-olateC5H10N2O250.10.60
1-amino-2-propanolC3H9NO50.10.60
2-ethylphenolC8H10O50.20.60
4-ethylphenolC8H10O50.20.60
butanolC4H10O50.20.60
2-amino-1-butanolC4H11NO50.20.60
furfuryl alcoholC5H6O250.30.60
tetrahydrofurfuryl alcoholC5H10O250.30.60
2,4-dimethylphenolC8H10O50.30.60
2-isopropylphenolC9H12O50.40.61
4-tert-butylphenolC10H14O50.40.61
benzyl alcoholC7H8O50.40.61
propanolC3H8O50.70.62
3,5-dimethoxyphenolC8H10O350.80.62
4-chloro-3-methylphenolC7H7ClO51.00.63
2-ethoxyethanolC4H10O251.00.63
ethyl (2S)-2-hydroxypropanoateC5H10O351.10.63
3-ethylphenolC8H10O51.60.65
2-aminoethanolC2H7NO51.80.65
1,5-pentanediolC5H12O251.90.65
2-methylphenolC7H8O51.90.65
ethanolC2H6O51.90.65
N-methylacetamideC3H7NO52.00.66
2-propen-1-olC3H6O52.10.66
tetraethylene glycolC8H18O552.20.66
4-bromophenolC6H5BrO52.20.66
4-cyanophenolC7H5NO52.20.66
2-methoxyethanolC3H8O252.30.67
1,2-butanediolC4H10O252.60.68
3-methylphenolC7H8O52.80.68
triethylene glycolC6H14O452.80.68
(+-)-1,3-butanediolC4H10O252.80.68
3-hydroxyphenyl acetateC8H8O353.20.69
4-methylphenolC7H8O53.30.70
phenolC6H6O53.40.70
1,4-butanediolC4H10O253.50.70
2-mercaptoethanolC2H6OS53.60.71
diethylene glycolC4H10O353.80.71
N-methylformamideC2H5NO54.10.72
1,2-propanediolC3H8O254.10.72
2,2,2-trichloroethanolC2H3Cl3O54.10.72
butanoic acidC4H8O254.40.73
4-chlorophenolC6H5ClO54.40.73
2,2'-sulfanediyldiethanolC4H10O2S54.50.73
2-chlorophenolC6H5ClO54.70.74
1,3-propanediolC3H8O254.90.75
propanoic acidC3H6O255.00.75
heptanoic acidC7H14O255.00.75
acetic acidC2H4O255.20.76
pentanoic acidC5H10O255.30.76
hexanoic acidC6H12O255.40.76
triethanolamineC6H15NO355.40.76
methanolCH4O55.40.76
2-chloroethanolC2H5ClO55.50.77
4-fluorophenolC6H5FO55.50.77
2-propynolC3H4O55.70.77
ethanediolC2H6O256.30.79
formamideCH3NO56.60.80
tri-n-butylammonium nitrateC12H28N2O356.70.80
1,2,3-propanetriolC3H8O357.00.81
dimethylammonium dimethylcarbamateC5H14N2O257.20.82
formic acidCH2O257.70.83
2,2,3,3-tetrafluoro-1-propanolC3H4F4O59.40.89
3-hydroxypropanenitrileC3H5NO59.60.89
2,2,2-trifluoroethanolC2H3F3O59.80.90
n-propylammonium nitrateC3H10N2O360.60.92
3-chlorophenolC6H5ClO60.80.93
n-butylammonium thiocyanateC5H12N2S61.40.95
sec-butylammonium thiocyanateC5H12N2S61.60.95
ethylammonium nitrateC2H8N2O361.60.95
ethylamine hydrochlorideC2H8ClN62.30.98
waterH2O63.11.00
di-n-propylammonium thiocyanateC7H16N2S63.31.01
1,1,1,3,3,3-hexafluoro-2-propanolC3H2F6O65.31.07