Okay, now we will continue with the second task.

How can a solvent influence the reaction rate?

Draw two diagrams to illustrate how a solvent can accelerate a chemical reaction and bring

an example of the process.

What do we have here?

We have different energy diagrams for the same reaction.

That is A and B, the products, and C and D, the products.

We have our transition state up here.

A small generation.

What is a transition state?

That is this temporary configuration of my products before they are produced.

Here the reaction takes place in three different solvents.

We have solvent 1 as a reference, and we also have solvent 2 and 3.

We also have delta G, in other words, the deactivation energy or the necessary energy

to reach this transition state, i.e. from my products.

We have the activation energy of the reaction here, when the different solvents are used.

For example, delta G, when the reaction takes place in solvent 1, i.e. in reference, here

for solvent 2 and here for solvent 3.

And we also have the changes in the activation energy, when we change from solvent 1 to

2 or from 1 to 3.

On the left side we have a case where the solvent accelerates the reaction speed.

And how does that happen?

It can be that the second solvent stabilizes the transition state better, i.e. better than

the reference solvent, or the transition state is more soluble in solvent 2 than in solvent

And since the new transition state is in a lower energy range, there is a reduction

of the activation energy and thus a higher reaction speed.

On the right side we have something else.

We have a case where my adducts are more soluble in solvent 3 than in 1.

They are, so to speak, shifted to a lower energy range.

And even if this solubility is better, this unfortunately brings a problem.

That is, that the energy needed, the necessary energy, is increased to reach my transition

state.

This means that the activation energy is higher in solvent 3 and of course the reaction speed

is unfortunately slowed down.

In summary, we can say that the solvent has a catalytic effect.

And just like with a catalyst, we have to understand or distinguish that the solvent

can influence the kinetics and selectivity of the reaction, but not the thermodynamics.

This is very important.

And bring an example of a process when the use of a solvent seriously influences on the

reaction rate or makes the process possible.

We have, for example, SN1 reactions that can get shrunk in the reaction.

Some SN1 reactions are favored by a protic polar solvent.

And normally this happens when a carbocation is created as a transition state.

Then the polar solvent can stabilize this carbocation and thus the reaction speed is

improved.

We also have SN2 reactions.

For example, here we have a Finkelstein reaction in acetone as a solvent.

In this case, for example, one of the products is not soluble in acetone, so sodium chloride

is not soluble.