Reactivity 3.3—Electron sharing reactions Flashcards
What is a radical in chemistry?
A radical is a species that contains an unpaired electron, making it highly reactive and unstable.
How does homolytic fission relate to radicals?
Homolytic fission is a process where a covalent bond breaks evenly, with each atom receiving one electron from the bond, leading to the formation of radicals.
Why are radicals so reactive?
Radicals are highly reactive due to their unpaired electron, which has a strong tendency to pair up, leading them to rapidly form more stable covalent bonds with other substances.
What role do UV rays play in the formation of radicals?
UV rays provide sufficient energy to cause homolytic fission of certain covalent bonds, such as those in halogens, resulting in the formation of radicals.
What is the significance of bond enthalpy in the context of radical formation?
Bond enthalpy indicates the amount of energy required to break a bond. Bonds with relatively low bond enthalpies, like those between two halogen atoms, are more susceptible to undergoing homolytic fission to form radicals.
How do CFCs contribute to ozone depletion through radical formation?
CFCs are broken down by UV radiation into highly reactive radicals, which then react with ozone, depleting the ozone layer and contributing to environmental concerns.
What is the mechanism for homolytic fission in radical formation?
The mechanism involves the use of single-barbed arrows (fish-hook arrows) to show the movement of a single electron from the covalent bond to the formation of two radicals.
What initiates a radical substitution reaction between alkanes and halogens?
The reaction is initiated by the formation of radicals, often through the dissociation of a diatomic halogen molecule under UV light, producing two halogen radicals.
What is the general mechanism for the substitution reaction of methane with chlorine?
The mechanism involves three steps: initiation (formation of radicals), propagation (radicals react to form new radicals and products), and termination (radicals combine to form stable molecules).
Define propagation in the context of radical substitution reactions.
Propagation steps involve a radical reacting with a stable molecule to form a new radical and a new stable molecule, perpetuating the chain reaction.
How does the termination step occur in radical substitution reactions?
Termination occurs when two radicals react together to form a stable molecule, effectively ending the chain reaction.
Describe the role of UV light in radical substitution reactions.
UV light provides the energy required to break the bond in diatomic halogen molecules, forming radicals that initiate the substitution reaction.
What is the significance of bond enthalpies in predicting the outcome of substitution reactions?
Bond enthalpies help predict the energy required for bond breaking and formation, influencing the feasibility and products of radical substitution reactions.
How do radical substitution reactions contribute to the synthesis of halogenoalkanes?
They allow for the introduction of halogen atoms into alkanes, converting relatively unreactive alkanes into more reactive halogenoalkanes, which are valuable in organic synthesis.
