The present computational study deals with the Diels-Alder reaction between anthracene derivatives and p-benzoquinone under mechanical stressing using an AM1 semiempirical method. During the reaction between free molecules, the dihedral angle (DHA) of anthracene reduces with decreasing intermolecular distance down to 150 o at the state of activated complex. This in mind, we try to mimic the solid state process by changing DHA. The highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gap (HLG) have been computed over DHA range between 180 o and 150 o . The HLGs and those with p-benzoquinone (intermolecular HLG) for anthracene, 9-methylanthracene, 9,10-dimethylanthracene, 9,10-bis(chloromethyl)anthracene and 9,10-bis(bromomethyl)anthracene decreased with decreasing the DHA. Thus, the decrease in the HLG favors the Diels-Alder reaction, in favor of the mechanochemical Diels-Alder reaction.