The reaction of the bifunctional organic molecule 1-dimethylamino-2-propyne (DMAP) on the Si(100) surface has been investigated by density functional calculations on a one-dimer cluster model. We found that, once in the physisorbed dative bonded well (-22.1 kcal mol(-1)), DMAP can proceed to react via a number of pathways. We first considered the cycloaddition of the C equivalent to C triple bond, leading to Si-C di-sigma bonded product (-58.6 kcal mol(-1)), computing an energy barrier of 33.1 kcal mol(-1). We considered also possible dissociative pathways of dative bonded DMAP, i.e., methylene C-H, methyl C-H or N-CH3 bond cleavage. (c) 2005 Elsevier B.V. All rights reserved.