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 (−22.1kcalmol −1 ), DMAP can proceed to react via a number of pathways. We first considered the cycloaddition of the CC triple bond, leading to Si–C di-σ bonded product (−58.6kcalmol −1 ), computing an energy barrier of 33.1kcalmol −1 . We considered also possible dissociative pathways of dative bonded DMAP, i.e., methylene C–H, methyl C–H or N–CH 3 bond cleavage.