Explain how carbon-halogen bond enthalpy affects reaction rate.

The carbon-halogen bond enthalpy is crucial in determining the reaction rate of halogenoalkanes. The bond enthalpy indicates the strength of the carbon-halogen bond; weaker bonds break more easily, facilitating nucleophilic substitution reactions. For example, the carbon-bromine bond has a lower bond enthalpy compared to the carbon-chlorine bond, making it more reactive. Thus, halogenoalkanes with weaker carbon-halogen bonds will undergo nucleophilic substitution at a faster rate due to the lower energy required to break these bonds, leading to a more efficient reaction pathway.