Interactions between adjacent particles of condensed phases can lead to quantum correlation phenomena. like quantum interference, entanglement, delocalization, and "Schrodinger's cat" states. Such correlations are theoretically expected to be extremely short-lived because of environmental disturbances. Here, we present experimental evidence for quantum entanglement between well localized protons of C-H bonds of 2-isobutoxyethanol dissolved in D2O. The applied experimental method is neutron Compton scattering (NCS), which has a characteristic time window in the subfemtosecond time range. Our NCS results reveal that, in the subfemtosecond time scale, the measured cross-section density, and thus, in simple terms, the effectively present concentration, of the H atoms is "anomalously" reduced by similar to 20%. Affecting the microdynamics of protons of covalent C-H bonds, this novel effect may have a broad range of chemical and biological applications.