Which refrigerants were targeted first for phaseout by the Montreal Protocol due to their high ozone depletion potential?

The refrigerants that were targeted first for phaseout by the Montreal Protocol are indeed the chlorofluorocarbons (CFCs). CFCs were found to have a significantly high ozone depletion potential (ODP), leading to serious environmental concerns regarding ozone layer depletion. The Montreal Protocol, signed in 1987, aimed to protect the ozone layer by phasing out substances that deplete it, with CFCs being the primary focus initially.

CFCs release chlorine atoms when they are broken down in the atmosphere, which then react with ozone (O3), leading to its depletion. This action was a major catalyst for the protocol's establishment, as the depletion of the ozone layer increases harmful ultraviolet radiation reaching Earth's surface, which can lead to various health and environmental issues.

Other options like HFCs (hydrofluorocarbons) and HCFCs (hydrochlorofluorocarbons) are not correct in this context. HFCs, while they do not deplete ozone, were developed as alternatives to CFCs and are now seen as having high global warming potential rather than ozone depletion potential. HCFCs were indeed subject to phaseout as well, but they were targeted later than C