In conclusion, we have demonstrated zero-field NMR as a method for reaction monitoring with chemical specificity by observing the hydrogenation of molecules with paraenriched hydrogen gas. We were able to extract J-couplings and their relative signs from the zero-field spectra, and additionally specify which proton pair in dimethyl succinate originated from the second p-H2 addition. For these experiments a commercial atomic magnetometer was used for signal detection. The advantages of this analytical technique are the ability to observe samples in metal containers, and not losing spectral resolution due to magnetic susceptibility inhomogeneity in the sample. We anticipate that ZULF NMR will find application in the field of catalysis for operando and in situ reaction monitoring, as well as the study of chemical reaction mechanisms under realistic conditions. We are exploring the possibility of implementing an array of magnetic sensors around a reactor for spatially-resolved chemical kinetics monitoring.