Here are the essential concepts you must grasp in order to answer the question correctly.
Free Radical Halogenation
Free radical halogenation is a reaction where alkanes react with halogens (like Cl2) in the presence of heat or light, leading to the substitution of hydrogen atoms with halogen atoms. This process involves the formation of free radicals, which are highly reactive species with unpaired electrons. The reaction typically proceeds through initiation, propagation, and termination steps, resulting in various halogenated products.
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Excess Reactant Effect
Using an excess of a reactant, such as Cl2, influences the reaction outcome by driving the reaction towards the formation of more halogenated products. In free radical halogenation, an excess of Cl2 can lead to multiple substitutions on the alkane, resulting in a major product that is heavily halogenated. This concept is crucial for predicting the major product in reactions where the halogen can replace multiple hydrogen atoms.
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Ultraviolet Light as a Catalyst
Ultraviolet (UV) light serves as a source of energy that initiates the free radical halogenation process by breaking the Cl-Cl bond in chlorine molecules, generating chlorine radicals. This initiation step is essential for the reaction to proceed, as it creates the reactive species needed for the substitution of hydrogen atoms in alkanes. Understanding the role of UV light helps in grasping how the reaction conditions affect product formation.
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