To explore the reactivities of alkene (-CH=CH
2) and carboxy (-COOH) group with H-Si under UVirradiation, the addition mechanism for the reactions of SiH
3 radical with propylene and acetic acid wasstudied by using the B3LYP/6-311++G(d,p) method. Based on the surface energy profiles, the dominantreaction pathways can be established; i.e., SiH
3 adds to the terminal carbon atom of the alkene (-CH=CH
2)to form an anti-Markovnikov addition product, or adds to the oxygen atom of the carboxy group (-COOH)to form silyl acetate (CH
3-COOSiH
3). Because the barrier in the reaction of the carboxy group (39.9 kJ/mol) is much larger than that of alkene (11.97 kJ/mol), we conclude that the reaction of bifunctional molecules(e.g.,
![](/images/gifchars/omega.gif)
-alkenoic acid) with H-Si under irradiation condition is highly selective; i.e., the alkene group (-CH=CH
2) reacts with SiH
3 substantially faster than the carboxyl group (-COOH), which agrees well with theexperimental results. This provides the possibility of preparing carboxy-terminated monolayers on siliconsurface from
![](/images/gifchars/omega.gif)
-alkenoic acids via direct photochemical reaction.