Complex sentence: Chemical systems cannot oscillate about a position of final equilibrium because such an oscillation would violate the second law of thermodynamics, which requires that a thermodynamic system which is not at equilibrium approach equilibrium and not recede from it.
Split into simpler sentences: Chemical systems cannot oscillate about a position of final equilibrium because such an oscillation would violate the second law of thermodynamics. For a thermodynamic system which is not at equilibrium, this law requires that the system approach equilibrium and not recede from it.