The lesser reactivity of the ester group could be understood by examining the partial density of states (pDOS), shown in Figure and ESI Figure . ESI Figure illustrates the partial density of states (pDOS) for the C, N, and O atoms of the three functional groups in the isolated 3Aa molecule. As shown in ESI-Figure , the 2p(O) and 2p(N) states of the nitro group, and the 2p(C) and 2p(N) states of the cyano group, exhibit occupied states that are relatively closer to the Fermi compared to the 2p(O) and 2p(C) states of the ester group rendering the ester group the least reactive. Figure displays pDOS of C, N, and O atoms of all the three functional groups of the 3Aa after adsorption on the Pd (111) surface. It could be noted from the Figure ) that the 2p(O) states of nitro and 2p(N) states of cyano groups demonstrate changes upon interaction with H2@Pd (111) whereas the least modifications are observed for pDOS of ester. Not only did the peak intensity decrease in both cases, but a broadening of the peak along with a secondary peak is observed in all the cases except for energetically the most stable one. Thus, the analysis of effective Mulliken charges and pDOS explains the activation observed in nitro and cyano functional groups and its absence in the ester. The efficiency of the heterogeneous catalyst was assessed by conducting reactions using the recovered catalyst. It was observed that with each successive cycle, the reaction time increased, accompanied by a slight decrease in yield, up to the fifth cycle (ESI-figure ). To check the stability of the Pd/C catalysts, several experiments were carried out using the recovered catalyst under the same optimized reaction condition. After each catalytic run, the catalyst was recovered by filtration, washed multiple times with methanol dried at 120 °C for overnight and used for the catalytic reaction without further pretreatment. The results show decrease in the yield of product using a Pd/C catalyst after every successive reaction. The X-ray diffraction pattern was examined which shows the formation and crystallinity of fresh and used catalyst. The diffraction peaks observed for Pd/C were at 2θ = 40.01° (111) and 46.7° (200) for Pd (JCPDS Card No. 00-005-0681) and at 2θ = 25.6° (002) for carbon (JCPDS Card No. 01-075-1621). Similar diffraction peaks were observed for both the fresh and used catalysts (Figure , Ib). The morphology data of fresh catalyst shows aggregated round spot and the average particle size of 2.47 nm. The morphology of used catalyst (after 5th cycle of reaction) shows less aggregated round spot and average particle size of 1.89 nm.