Lewis donor strength

Lewis bases can be ordered accoring to strength using the entalphy of reaction with different Lewis acids. The strength depends of the choice of acid and the ranking of the bases can therefore change somewhat.
The two most popular scales are Gutmann's donor number (DN), which uses SbCl5 as the acid, and the BF3-scale of Maria & Gal. Because SbCl5 is fairly reactive some Donor Numbers have been determined by indirect methods.
There is a fairly strong correlation between the two scales (→ BF3-scale vs DN) as well as between DN (→ SB vs DN) and the BF3-scale (→ SB vs BF3) respectively, and → Catalan's SB solvent polarity parameter.

See → "The donor-acceptor approach to molecular interactions" by V. Gutmann (of mainly historical interest [1978]) and
"Lewis Basicity and Affinity Scales: Data and Measurement" by C. Laurence and J.-F. Gal (for a recent [2009] and comprehensive overview of Lewis basicity).

Note that the DN scale, for historic reasons, is given in kcal/mol whereas the BF3-scale is in kJ/mol.

NameFormulaGal BF3DN
2,2,4,4-tetramethyl-3-pentanoneC9H18O31.310.3
nitrobenzeneC6H5NO235.84.4
nitromethaneCH3NO237.62.7
chloroacetonitrileC2H2ClN44.010.0
1,3,2-dioxathiolan-2-oxideC2H4O3S50.015.3
sulfolaneC4H8O2S51.314.8
benzonitrileC7H5N55.411.9
2-phenylacetonitrileC8H7N56.615.1
methyl benzoateC8H8O259.415.0
2-methylpropanenitrileC4H7N60.115.4
acetonitrileC2H3N60.414.1
propanenitrileC3H5N61.016.1
butanenitrileC4H7N61.216.6
ethyl benzoateC9H10O261.215.0
N,N-dimethyltrifluoroacetamideC4H6F3NO61.616.6
benzophenoneC13H10O62.916.0
4-methyl-2-oxo-1,3-dioxolaneC4H6O364.215.1
1,3-dioxolan-2-oneC3H4O366.416.4
dimethyl carbonateC3H6O367.617.2
2,4-dimethyl-3-pentanoneC7H14O68.116.2
1,3-dioxolaneC3H6O268.621.2
diethyl carbonateC5H10O371.016.0
ethyl formateC3H6O271.217.0
N,N-dimethylcarbamoyl chlorideC3H6ClNO72.217.2
3-pentanoneC5H10O72.315.0
methyl acetateC3H6O272.816.5
3,3-dimethyl-2-butanoneC6H12O72.817.0
dioxaneC4H8O274.114.3
acetophenoneC8H8O74.515.0
1,2-dimethoxyethaneC4H10O274.720.0
3-methyl-2-butanoneC5H10O74.817.1
benzaldehydeC7H6O74.916.0
4-methyl-2-pentanoneC6H12O75.116.0
oxolan-2-oneC4H6O275.118.0
ethyl acetateC4H8O275.617.1
2-propanoneC3H6O76.017.0
2-butanoneC4H8O76.117.4
2-pentanoneC5H10O76.217.5
cyclohexanoneC6H10O76.418.0
diisopropyl etherC6H14O76.619.0
dimethylcyanamideC3H6N277.217.0
cyclopentanoneC5H8O77.418.0
dibutyl etherC8H18O78.619.0
diethyl etherC4H10O78.819.2
dipropyl etherC6H14O79.418.0
N,N-dimethylurethaneC5H11NO284.222.4
trimethyl phosphateC3H9O4P84.823.0
oxaneC5H10O85.422.0
tetrahydrofuranC4H8O90.420.0
2-methyltetrahydrofuranC5H10O92.812.0
1,3-dimethyl-2-imidazolidinoneC5H10N2O98.927.7
dimethyl sulfoxideC2H6OS105.329.8
dibutyl sulfoxideC8H18OS107.631.0
N,N,N',N'-tetramethylureaC5H12N2O108.631.0
N,N-dimethylanilineC8H11N109.227.0
N,N-dimethylformamideC3H7NO110.526.6
1-methylazepan-2-oneC7H13NO111.427.1
1,3-dimethyltetrahydropyrimidin-2(1H)-oneC6H12N2O112.133.0
N,N-dimethylacetamideC4H9NO112.127.8
N-methylpyrrolidoneC5H9NO112.627.3
N,N-diethylformamideC5H11NO113.230.9
N,N-diethylacetamideC6H13NO113.632.2
hexamethylphosphoramideC6H18N3OP117.538.8
1-di(piperidin-1-yl)phosphorylpiperidineC15H30N3OP118.140.9
tripyrrolidinophosphine oxideC12H24N3OP122.547.2
pyridineC5H5N128.133.1
3-methylpyridineC6H7N130.939.0
4-methylpyridineC6H7N134.234.0
triethylamineC6H15N135.961.0