Abstract: In this study, the interaction of Busulfan anticancer drug with PEG-modified cellulose was investigated. The impacts of the stereo electronic effect associated with donor-acceptor electron delocalizations, dipole-dipole interactions, and total steric exchange energies on the structural and electronic properties and reactivity of modified cellulose in interaction with Busulfan anticancer drug was studied based on the Density Functional Theory (DFT) calculations by using B3LYP/(6-31G, 6-31G*) level of theory in the gas phase, and water solution. Thermodynamic functional analysis indicates that the relative energies (ΔE), free Gibbs energies (ΔG) and enthalpies (ΔH) are negative for of Busulfan anticancer drug-PEG-modified cellulose system, but the calculated entropies (ΔS) are Positive, suggesting thermodynamic favorability for covalent attachment of dye on PEG-modified cellulose and these results confirm the structural stability of the Busulfan in gas phases. Delocalization of charge density between the bonding or lone pair and antibonding orbitals calculated by NBO (natural bond orbital) analysis. The calculated LUMO-HOMO energy bond gap shows that charge density transfer occurs within the molecules and the semi-conductivity of PEG could be justified. Also, based on the parameters obtained for the Busulfan drug in the absence of cellulose, it can be said that due to the presence of cellulose, the interaction between the electronegative oxygen atom of cellulose and the carbons of Busulfan has the least electron coverage and is more affected by the external magnetic field, so They have the lowest σiso and the highest δ or chemical shift, but in the absence of cellulose, carbon does not interact with oxygen, it has the highest electron coverage and appears in the 13CNMR spectrum at a lower δ chemical shift.Abstract: In this study, the interaction of Busulfan anticancer drug with PEG-modified cellulose was investigated. The impacts of the stereo electronic effect associated with donor-acceptor electron delocalizations, dipole-dipole interactions, and total steric exchange energies on the structural and electronic properties and reactivity of modified cellulose ...Show More