Saturated hydrocarbons are unreactive due to the stability of their carbon-carbon single bonds. However, in the presence of sunlight, chlorine undergoes rapid substitution reactions with hydrocarbons, breaking the carbon-hydrogen bonds and forming new carbon-chlorine bonds.
Why are saturated hydrocarbons generally unreactive, but undergo rapid reactions with chlorine in sunlight?
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Saturated hydrocarbons are generally unreactive due to the strength and stability of carbon-carbon single bonds. However, they undergo rapid reactions with chlorine in sunlight due to the presence of ultraviolet (UV) light. UV light provides the energy needed to break the relatively strong carbon-hydrogen (C-H) and carbon-carbon (C-C) bonds, initiating free radical substitution reactions. The chlorine radicals formed in this process readily substitute hydrogen atoms in the hydrocarbon, resulting in the formation of chlorinated products. This reaction is specific to the presence of sunlight and is a characteristic feature of alkanes reacting with halogens under these conditions.