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.

Name	Formula	Gal BF₃	DN
1,2-dimethoxyethane	C₄H₁₀O₂	74.7	20.0
1,3,2-dioxathiolan-2-oxide	C₂H₄O₃S	50.0	15.3
1,3-dimethyl-2-imidazolidinone	C₅H₁₀N₂O	98.9	27.7
1,3-dimethyltetrahydropyrimidin-2(1H)-one	C₆H₁₂N₂O	112.1	33.0
1,3-dioxolan-2-one	C₃H₄O₃	66.4	16.4
1,3-dioxolane	C₃H₆O₂	68.6	21.2
1-di(piperidin-1-yl)phosphorylpiperidine	C₁₅H₃₀N₃OP	118.1	40.9
1-methylazepan-2-one	C₇H₁₃NO	111.4	27.1
2,2,4,4-tetramethyl-3-pentanone	C₉H₁₈O	31.3	10.3
2,4-dimethyl-3-pentanone	C₇H₁₄O	68.1	16.2
2-butanone	C₄H₈O	76.1	17.4
2-methylpropanenitrile	C₄H₇N	60.1	15.4
2-methyltetrahydrofuran	C₅H₁₀O	92.8	12.0
2-pentanone	C₅H₁₀O	76.2	17.5
2-phenylacetonitrile	C₈H₇N	56.6	15.1
2-propanone	C₃H₆O	76.0	17.0
3,3-dimethyl-2-butanone	C₆H₁₂O	72.8	17.0
3-methyl-2-butanone	C₅H₁₀O	74.8	17.1
3-methylpyridine	C₆H₇N	130.9	39.0
3-pentanone	C₅H₁₀O	72.3	15.0
4-methyl-2-oxo-1,3-dioxolane	C₄H₆O₃	64.2	15.1
4-methyl-2-pentanone	C₆H₁₂O	75.1	16.0
4-methylpyridine	C₆H₇N	134.2	34.0
acetonitrile	C₂H₃N	60.4	14.1
acetophenone	C₈H₈O	74.5	15.0
benzaldehyde	C₇H₆O	74.9	16.0
benzonitrile	C₇H₅N	55.4	11.9
benzophenone	C₁₃H₁₀O	62.9	16.0
butanenitrile	C₄H₇N	61.2	16.6
chloroacetonitrile	C₂H₂ClN	44.0	10.0
cyclohexanone	C₆H₁₀O	76.4	18.0
cyclopentanone	C₅H₈O	77.4	18.0
dibutyl ether	C₈H₁₈O	78.6	19.0
dibutyl sulfoxide	C₈H₁₈OS	107.6	31.0
diethyl carbonate	C₅H₁₀O₃	71.0	16.0
diethyl ether	C₄H₁₀O	78.8	19.2
diisopropyl ether	C₆H₁₄O	76.6	19.0
dimethyl carbonate	C₃H₆O₃	67.6	17.2
dimethyl sulfoxide	C₂H₆OS	105.3	29.8
dimethylcyanamide	C₃H₆N₂	77.2	17.0
dioxane	C₄H₈O₂	74.1	14.3
dipropyl ether	C₆H₁₄O	79.4	18.0
ethyl acetate	C₄H₈O₂	75.6	17.1
ethyl benzoate	C₉H₁₀O₂	61.2	15.0
ethyl formate	C₃H₆O₂	71.2	17.0
hexamethylphosphoramide	C₆H₁₈N₃OP	117.5	38.8
methyl acetate	C₃H₆O₂	72.8	16.5
methyl benzoate	C₈H₈O₂	59.4	15.0
N,N,N',N'-tetramethylurea	C₅H₁₂N₂O	108.6	31.0
N,N-diethylacetamide	C₆H₁₃NO	113.6	32.2
N,N-diethylformamide	C₅H₁₁NO	113.2	30.9
N,N-dimethylacetamide	C₄H₉NO	112.1	27.8
N,N-dimethylaniline	C₈H₁₁N	109.2	27.0
N,N-dimethylcarbamoyl chloride	C₃H₆ClNO	72.2	17.2
N,N-dimethylformamide	C₃H₇NO	110.5	26.6
N,N-dimethyltrifluoroacetamide	C₄H₆F₃NO	61.6	16.6
N,N-dimethylurethane	C₅H₁₁NO₂	84.2	22.4
N-methylpyrrolidone	C₅H₉NO	112.6	27.3
nitrobenzene	C₆H₅NO₂	35.8	4.4
nitromethane	CH₃NO₂	37.6	2.7
oxane	C₅H₁₀O	85.4	22.0
oxolan-2-one	C₄H₆O₂	75.1	18.0
propanenitrile	C₃H₅N	61.0	16.1
pyridine	C₅H₅N	128.1	33.1
sulfolane	C₄H₈O₂S	51.3	14.8
tetrahydrofuran	C₄H₈O	90.4	20.0
triethylamine	C₆H₁₅N	135.9	61.0
trimethyl phosphate	C₃H₉O₄P	84.8	23.0
tripyrrolidinophosphine oxide	C₁₂H₂₄N₃OP	122.5	47.2