An analysis is accomplished for a natural convective flow of an isochoric and chemically reactive viscid fluid around an impetuously commenced oscillating vertical cylinder encapsulated in a porous structure. The governing problem comprising of a system of conjoined nonlinear boundary layer equations with adapted boundary conditions are solved numerically by a Crank-Nicholson scheme. This scheme is one among the finite difference schemes which is an implicit, unconditionally stable and convergent scheme. The impacts of appurtenant parameters of an oscillating cylinder on velocity, temperature, concentration, viscous drag, exchange of thermal energy and mass transfer are presented graphically and interpreted. Major findings of the study disclose the fact that oscillations with higher phase angle reinforce the rate of heat and mass transfer. The behaviors of the streamlines and isotherms of the fluid are also presented and discussed.