Table 1.

Strengths of Interaction (α-values) of Alkyl Ureas with Amide and Hydrocarbon Unified Atoms^a

Unfied atom	α (cal mol−1 molal−1 Å−2)b
Solute	Amide O	Amide N	Aliphatic sp3C	Amide sp2C	Aromatic sp2C
urea	−0.52 ±0.04	−0.09 ±0.02	−0.07 ±0.01	−0.69 ±0.06	−0.59 ±0.01
mu	0.52 ±0.08	−0.44 ±0.03	−0.31 ±0.01	−0.99 ±0.07	−1.37 ±0.08
eu	0.79 ±0.06	−0.55 ±0.02	−0.43 ±0.01	−1.2 ±0.05	−1.62 ±0.07
1,1 -dmu	1.09 ±0.07	−0.61 ±0.03	−0.35 ±0.01	−1.53 ±0.05	−2.05 ±0.08
1,3-dmu	1.68 ±0.09	−0.77 ±0.03	−0.56 ±0.01	−1.87 ±0.06	−1.97 ±0.04
1,1-deu	1.73 ±0.09	−0.84 ±0.03	−0.64 ±0.01	−1.88 ±0.07	−2.72 ±0.1
1,3-deu	2.35 ±0.09	−1.01 ±0.04	−0.76 ±0.01	−2.28 ±0.07	−2.97 ±0.13
naphthalene	−4.44 ± 0.8	0.85 ±0.29	−2.71 ±0.07	−2.88 ±0.83	---c

^aSolute abbreviations: mu: methylurea; eu: ethylurea; dmu: dimethylurea; deu: diethylurea;

^bα-values are obtained by fitting experimental μ₂₃ values (Tables S2 and S3) for amide-amide interactions to Equations 3, and for amide-aromatic interactions to Equation 4. Propagated uncertainties in α-values are calculated as described previously.¹⁹

^cNot determined.