What is single molecule reaction, bimolecular reaction, multimolecular reaction.

Single-molecule reactions are one of the reaction mechanisms, which are characterized by the fact that only one reactant molecule is involved in the step that determines the reaction rate. In physical chemistry, a single-molecule reaction may or may not be a first-order reaction.

Bimolecular reactions, one of the meta-reaction types, are characterized by a change between the molecules of two reactants involved in the step that determines the reaction rate.

Multimolecular reactions, one of the meta-reaction types, are characterized by the fact that they involve changes between multiple reactant molecules in the steps that determine the reaction rate.

1. Single-molecule reaction: In the process of nucleophilic substitution reaction, the first is the bond heterocleavage between the departing group and the central carbon atom (see heterocleavage reaction) to generate an unstable positive carbon ion, which is a slow step; The second is the positive carbon ion intermediate rapidly with nucleophiles.

nu: (or nu:) to form a new key.

2. Bimolecular reaction.

In the process of nucleophilic substitution, the bond between the central carbon atom and the leaving group L: is broken, and the nucleophile nu: forms a new bond with the central carbon atom, in this step of the reaction, the nucleophile attacks the central carbon atom from the back of the leaving group, and when the nucleophile gradually approaches the central carbon atom to form a new bond, the leaving group is gradually pushed out of the central carbon atom and the original bond is broken, and the two are synergistically carried out.

In rare cases, there are three-molecule reactions, and there are no four-molecule or more reactions.

The classification of this type of reaction is based on the number of molecules involved in the rate control step that determines the speed of the reaction. For example, the hydrolysis of tert-butyl chloride has only one molecule involved in the step that determines the reaction speed, so it is a single-molecule reaction.

Primitive reactions are usually unimolecular or bimolecular reactions, with rare cases of three-molecule reactions and no four-molecule or more reactions. The number of reaction orders of a motif reaction is equal to the number of reaction molecules.

There are the following differences.

1. The reaction mechanism is different.

Single-molecule reaction: A change in only one reactant molecule is involved in the step.

Bimolecular reactions: A step involves a change between two reactant molecules.

2. The reaction rate is different.

Single-molecule reactions: The reaction rate is only proportional to the concentration of the reactants, not the concentration of the nucleophile.

Bimolecular reactions: The reaction rate (r) is directly proportional to the concentration of the reactant and the concentration of the nucleophile.

The main differences are that the properties, characteristics, and principles are different, as follows:

First, the nature is different.

1. Single-molecule reaction.

Single-molecule reaction is one of the reaction mechanisms.

2. Bimolecular reaction.

Bimolecular reactions, one of the meta-reaction types.

Second, the characteristics are different.

1. Single-molecule reaction.

is a change in the molecule of only one reactant involved in the step that determines the rate of the reaction.

2. Bimolecular reaction.

is in the step that determines the rate of the reaction and involves the change between the molecules of the two reactants.

Third, the principle is different.

1. Single-molecule reaction.

The overall reaction rate is determined only by the first slow step. Since only one reactant (RL) molecule participates in the slow step that determines the reaction rate, the reaction performed by this process is generally referred to as a single-molecule nucleophilic substitution reaction SN1 (S for substitution, N for nucleophile, and 1 for single molecule).

In the process of single-molecule nucleophilic substitution, the dissociation rate depends on the stability of the positive carbon ion intermediate formed after dissociation, which is the step that determines the overall reaction rate. The bonding of the dissociated positive carbon ion intermediate to the nucleophile is a step that does not determine the reaction rate. The reaction rate is only proportional to the concentration of the reactant and not to the concentration of the nucleophile:

Reaction rate = K1 [RL].

2. Bimolecular reaction.

Since there are two reactant molecules involved in the formation of the transition state, and the rate of the reaction depends on both Rl and Nu, the reaction that follows this process is called a bimolecular nucleophilic substitution reaction SN2 (S for substitution, N for nucleophilic, and 2 for bimolecule). In the SN2 reaction, the nucleophile attacks the central carbon atom from the back of the departing group, thus causing the configuration transformation of the chiral carbon atom

As the reaction progresses, the carbon atom changes from sp hybridization to sp hybridization, and the p orbital on the carbon atom overlaps with the electron cloud of nucleophile and the leaving group, respectively, and then the carbon atom changes from sp hybridization to sp hybridization, and the configuration transformation occurs at the same time

The reaction rate (R) of the bimolecular reaction is proportional to the concentration of the reactant and the concentration of nucleophile: R=K【RL】【Nu】

Bimolecular nucleophilic substitution reaction (SN2) is a class of nucleophilic substitution reactions, where S stands for substitution, N stands for nucleophilic, and 2 represents the rate-determining step of the reaction involving two molecules.

The SN2 reaction is a reaction caused by the collision between the starting substance and the anion Y, so it is called a bimolecular reaction. There is only 1 stage of the SN2 reaction. From the perspective of the Gyeongjue structure, the curved arrow stretched out by y indicates that the electron pair on y is attacking.

In addition, the arrow pointing to x by the c-x bond indicates that the valence electron pair of the c-x bond separates from the molecule, moves to x, and becomes the electron pair of x.

Factors that determine the rate of bimolecular nucleophilic substitution reactions.

1. The alkalinity of the departing group.

The more basic the leaving group, the weaker its ability to leave and vice versa. The alkalinity of the ion decreases as the period in which it is located. For halogen ions, iodide ions are the weakest in alkalinity, so iodide ions are a good leaving group; Fluoride ions, on the other hand, make it difficult for fluorinated hydrocarbons to react with SN2.

Basic f-cl-br-i-, the ability to leave is reversed from the order described above.

2. Nucleophilicity of nucleophiles.

Nucleophilicity needs to be distinguished from the basicity above. Alkalinity is the affinity of the reagent to protons, while nucleophilicity is the ability of the reagent to touch carbon atoms when they form a transition state. Generally speaking, the more electronegative, alkaline, and polarizable a reagent is, the stronger its nucleophilicity.

In fact, it is often necessary to consider a combination of these factors as well as the influence of solvents.

Answer: Matter is a single-molecule reaction, v=kc (h2o2$ bimolecular reaction, v=kc2

no2；$ single molecule reaction, v = kc (ho2

NO2$ bimolecular reaction, v = kc(co)c(no2$ bimolecular reaction, v = kc(noCl)c(Cl)$ trimolecular reaction, v = kc(ho)c(NO2

c(ar)。Block.

The gas-phase bimolecular motif reaction A + B P, the simple collision theory says:

Gas molecules A and B are both considered to be rigid spheres with no interaction (independent subons) and no internal structure that is completely elastic. Gas molecules A and B have to collide in order for a reaction to occur. The A and B molecules that collide are usually called colliding molecular pairs, referred to as molecular pairs; Only molecular pairs whose relative translational kinetic energy at the time of collision is greater than a certain energy threshold (c) can react, and this kind of collision that can react is called an effective collision.

During the reaction, the velocity of the gas molecules and the energy are still in equilibrium with the boltzmann balance.

That's what this passage describes.

In fact, it is too complicated to get the formula without simplifying, and the more time is wasted in the process.

We don't understand what it means, but you can see for yourself what you mean, do you understand?

In the process of nucleophilic substitution, the first step is to remove the bond between the departing group and the central carbon atom (see Heterocleavage Reaction Fluid) to generate an unstable positive carbon ion, which is a slow step. In the second step, the positive carbon ion intermediate rapidly binds to the nucleophile nu: (or nu:) to form a new bond: