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. 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.
It 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 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

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