Enthalpies of dilution of aqueous solutions of L-alpha-cysteine, L-alpha-histidine, L-alpha-asparagine, L-alpha-glutamine, L-alpha-arginine, L-alpha-tryptophan, and L-alpha-glutamic acid in water at a temperature of 298.15 K have been measured. The values of dilution enthaply were used to determine enthalpic homogeneous pair interaction coefficients which characterize the interactions between zwitterions of the examined L-alpha-amino acids in water. Approachable literature data of hydrophobic scales have been analyzed to obtain average values. The obtained values of enthalpic pair interaction coefficients have been put together with an average hydrophobic scale.