A set of notes given to us wrote that the rate-determining step is the propagation step. This seems to go against my understanding of the chemistry of this reaction. The step that likely has the highest activation energy should be the initiation step as it is the only step that involves bond-breaking solely.
Table of Contents
What is the rate-determining step of radical halogenation?
The hydrogen abstraction by the halogen radical, is the rate-determining step in radical halogenation. The alkyl radicals are also very reactive, and they react with the chlorine gas producing a new chlorine radical.
What is a propagation step in a radical reaction?
The propagation phase describes the ‘chain’ part of chain reactions. Once a reactive free radical is generated, it can react with stable molecules to form new free radicals. These new free radicals go on to generate yet more free radicals, and so on.
What is the rate-determining step in free radical polymerization?
Table 2.1 illustrates the steps in free-radical polymerizations. Formation ofinitiating radicals is the rate-determining step in the initiation reaction. The process can result, as shown in Table 2.1, from cleavage of compounds, like peroxides, or from other sources. Many reactions lead to formations of free radicals.
What is the rate-determining step in halogenation of alkanes?
The reactivity order of halogenation of alkanes is F2>Cl2>Br2>I2 .
How many steps are there in a free radical halogenation reaction?
The radical chain mechanism is characterized by three steps: initiation, propagation and termination.
How do you identify initiation propagation and termination steps?
What is a propagation step?
Two or more propagation steps: A propagation step is a reaction in which a radical is consumed and a new radical is generated. Propagation does not affect the concentration of radicals in the system.
What is the difference between initiation and propagation?
Initiation requires an input of energy but after that the reaction is self-sustaining. The first propagation step uses up one of the products from initiation, and the second propagation step makes another one, thus the cycle can continue until indefinitely.
What is the rate-determining step in the free radical bromination of methane?
Answer and Explanation: – Br−Br→2Br B r − B r → 2 B r is the rate-determining step.
Which is the rate-determining step of chain initiation step?
Which is the rate determining step of chain initiation step? Explanation: Initiator decomposition step is the rate determining step of chain initiation step as it is the slowest of two.
What is the first step of the radical substitution of alkanes?
The first step of free radical substitution is initiation step, where the chlorine to chlorine bond undergoes homolytic fission to form 2 chlorine atoms or radicals. The radicals are extremely reactive and kickstarts the reaction, hence we call this the initiation step.
What are the three steps in free radical polymerization?
Free Radical Polymerization occurs in three steps, i.e. Initiation, Propagation and Termination. Free Radical Polymerization is an essential technique for obtaining different polymers and material composites. It was used to get 40 billion of 110 billion polymers in the United States in 2001.
What is the limiting step in the free radical chain polymerization?
It was found that the rate-limiting step is the initiation step, that is, the rate constant for initiator dissociation is much smaller than that for monomer addition. Some of the monomers may also undergo other reactions such as combination with another radical to form inactive molecules.
What affects rate of polymerization?
The growth rate increases linearly with the concentration of monomer, and as the square root of the initiator concentration. The rest of the factors are just constants, so we can think of the rate law as one combined constant and those two concentration dependences.
How do you determine halogenation?
What are the important factors that influence the orientation of halogenation of alkanes?
Halogenation of an alkane requires the presence of heat or light.
Which element is most selective in its halogenation?
The fluorine radical is the most reactive of the halogen radicals, and it reacts violently with alkanes. In contrast, the iodine radical is the least reactive of the halogen radicals. in fact, it is so unreactive that it is unable to abstract a hydrogen atom from an alkane.
What is the mechanism of free radical halogenation?
Radical halogenation (free radical halogenation): A substitution reaction in which a hydrogen atom is replaced with a halogen atom, via a free radical reaction mechanism. Industrial scale synthesis of chloromethane (CH3Cl) is achieved by gas-phase radical halogenation of methane with chlorine.
What are the three steps in radical reaction use the chlorination of methane as your basis?
- Step 1: Initiation.
- Step 2: Propagation.
- Step 3: Termination.
What is the order of reactivity of halogen in free radical halogenation?
Order of reactivity towards halogenation is F2>Cl2>Br2>I2.
What is the characteristic of a radical chain initiation step?
Radical chain reactions have three distinct phases: initiation, propagation, and termination. The initiation phase describes the step that initially creates a radical species. In most cases, this is a homolytic cleavage event, and takes place very rarely due to the high energy barriers involved.
What type of reaction is reaction a initiation propagation termination?
8. Summary: Free-Radical Substitution Reactions. These three types of steps are encountered in every free-radical reaction. The bottom line here is that by counting the number of radicals created or destroyed in each step, you can determine if the step is initiation, propagation, or termination.
What is the correct process of initiating a reaction?
A chemical chain reaction proceeds by a sequence generally subdivided into three stages: (1) Initiation, in which a reactive intermediate, which may be an atom, an ion, or a neutral molecular fragment, is formed, usually through the action of an agent such as light, heat, or a catalyst.
What is first propagation step?
In the first propagation step, a chlorine radical combines with a hydrogen on the methane. This gives hydrochloric acid (HCl, the inorganic product of this reaction) and the methyl radical.