The reaction pathways of aqueous chlorination of anisole, ethylbenzene and o-methoxybenzoic acid being structural fragments of humic matter were studied using gas chromatography-mass spectrometry. Chlorine and sodium hypochlorite were used as commonly employed disinfecting agents. Comparison of the chlorinating agents was performed in terms of the assortment and relative amounts of reaction products. Detailed schemes of the selected substrates transformation were proposed. Quantum chemical calculations were applied to propose structures of the reacting particles and a numerical parameter to estimate an extent of conversion of aromatic substrates during chlorination.