The enthalpy of immersion of closed-end carbon nanotubes in a series of organic liquids has been measured. The enthalpy was found to be linear function of the dipole moments. From the slope of the lines the average electrostatic field strength of the surface was calculated. This value increases with the decrease in tube radius. The curved aromatic fragments of C24H12 have been employed as models of carbon nanotubes (n, 0), where n varies from 30 up to 180. Theoretical results indicate that the reactivity indices also depend strongly on the surface curvature being linearly correlated with the surface electrostatic field strength. (C) 2009 Elsevier B.V. All rights reserved.