Theoretical study on the mechanism for the addition reaction of SiH(3) with propylene and acetic acid.
To explore the reactivities of alkene (-CH=CH(2)) and carboxy (-COOH) group with H-Si under UV irradiation, the addition mechanism for the reactions of SiH(3) radical with propylene and acetic acid was studied by using the B3LYP/6-311++G(d,p) method. Based on the surface energy profiles, the dominant reaction 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., omega-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 the experimental results. This provides the possibility of preparing carboxy-terminated monolayers on silicon surface from omega-alkenoic acids via direct photochemical reaction.
Liu
Yongjun
Y
School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China. yongjunliu_1@sdu.edu.cn
Wang
Zhiguo
Z
Suo
Yourui
Y