Abstract: The electronic structure of ethenyl phenyl ether(ethenyloxy benzene) and the orientation effect of the ethenyloxy on electrophilic aromatic substitution are studied.The results show that the energy and atomic charge of ethenyl phenyl ether  are influenced by the space location of the ethenyloxy,and so is the orientation effect of the ethenyloxy on the reaction of electrophilic aromatic substitution. The molecular conformation is formed by the O—Ph bond rotation,the difference between the maximal and minimal protential energy of conformations ΔE is only 0.005 402 a.u..The potential energy of the molecule is at a minimum when  O₁₂—C₁C₁₃ is vertical to  benzene ring.The ethenyloxy is an electron-withdrawing group,but there is more negative charge of ortho-carbon atom  than that  of benzene carbon.The ortho electrophilic substitution reaction intermediate is the most stable. The products of ortho-substituted by the carbocation dehydrogenation shown to the ethenyloxy is ortho- and para- directing group.

Key words: ethenyl phenyl ether, electronic structure, ethyleneoxy, orientation effect