p-xylene monolayers were adsorbed at monolayer graphite covered Pt(111
) surfaces. The reactions of xylene with thermal D atoms were characte
rized with vibrational (HREELS) and thermal desorption (TDS) spectrosc
opies. Four reaction steps could be identified to proceed in the layer
s exposed to D. In a fast step D atoms add to the aromatic ring stepwi
se breaking double bonds thereby transferring the ring C atoms to sp(3
) hybridization. In a second also fast step, H atoms in methyl groups
at aromatic rings undergo an abstraction reaction to HD with a benzyl
radical as an intermediate which is pi-stabilized. Subsequently, the m
ethylene group is saturated by D addition. A third slow step is H abst
raction from the cyclohexane ring with subsequent D addition. In a fou
rth slow step the remaining I-I atoms in the methyl groups get exchang
ed by D towards fully deuterated dimethyl-cyclohexane as the final pro
duct. The reactions observed resemble striking similarities with the r
espective reactions in an organic chemistry environment.