High-resolution ALMA millimeter-band images show no significant offset between the peak of H2 emission in the photon-dominated region and CO(3-2) and HCO+(4-3) emission toward the molecular region in Orion Bar (Goicoechea et al., Nature, 2016). We verify whether time-dependent astrochemical calculations could reproduce nearly coincident positions of the H2 and CO dissociation fronts. We use chemo-dynamical model MARION (Kirsanova et al., ARep, 2009; Akimkin et al., MNRAS, 2015, 2017) to predict positions of the H2 and CO dissociation fronts relative to the ionization front on the interface between the Orion Bar and the Orion Nebula. We present results of three calculations with different dust models: MRN, Weingartner & Draine for Rv=3.1, and Weingartner & Draine for Rv=5.5 to study the effect of self and mutual shielding on the H2 and CO dissociation front positions. We find that in all the three models gas expansion velocity is nearly the same. The absence of the significant (more than 5 arcsec) offset between the H2 and CO dissociation fronts is obvious after 2000-3000 years of the gas expansion and shock propagation into the molecular gas. At the same time the offset of about 5 arcsec between CO(3-2) and HCO+(4-3) peak emission is visible in Orion. We see this small offset in our results utilizing RADEX modeling in the very beginning of the shock propagation prior to the time when the fronts of H2 and CO dissociation coincide. Our models predict that HCO+ is converted to CO in the shocked layer but at later computational times the shocked layer is too thin to be resolved by ALMA.