Scale-up Suite Help
Reactions
What is the Reactions in section?

The model will have a Reactions in section for each phase where reactions occur. By default, there is a Reactions in Solution section. For a biphasic system, you might have a Reactions in Organic and a Reactions in Aqueous section. The phases are named and defined in the Process Scheme section, and the names of the Reactions in sections come from the phase names.

Reactions in Solution for the Heck reaction model

In the Heck Reaction model, the Overall Reaction between 4-bromobenzaldehyde and butyl acrylate in the presence of a palladium catalyst is broken down into elementary steps. The catalytic cycle for the Heck reaction is given below:

 

 This can be written into Reactions in Solution as follows. Please note that the Na cation and NaBr has been omitted for clarity.

 

Description of Reactions in Solution

 When you scroll down to the Reactions in Solution section, it will look like this:

Firstly, at the top, Tref is given. The default value for this is 25C. The rate constants shown in the reaction lines are for this temperature only.  

Below the Reaction in Solution header is the column ||. Click the box to put a check in this column if you want to comment out the reaction. When it is checked, the reaction will be grayed out and will not be exported to Excel (if you do this later). Additionally, if the model is run in Simulator, this reaction will not be included in the model calculations.

Id: the is the reaction Id. By default, this is rxn1, rxn2, rxn3,....rxnN.

To the right of this column, the reaction is typed in. When you enter a new reaction, this is the first information you will enter. Reaction Lab provides helpful guidance to define each reaction, allowing you to choose materials from those defined in the Materials section, and reaction arrows for irreversible and reversible reactions.

The column to the right of this is called Bal. (This column is only visible when you click on the  icon.) This checks if the reaction is mass balanced based on the reaction and molecular weights of the materials.

The [+/-] column checks if the reaction is charge balanced based on the reaction and the charges given for the materials. (This column is only visible when you click on the  icon.)

The next four columns (k>, Ea>, Keq and Ea<) are used to input estimates for the reaction parameters. These are typically regressed from your experimental data. (These columns are only visible when you click on the  icon.)

Forward rate: This is the forward rate expression based on the number of reactants in the reaction.

Backward rate: This is the backward rate expression based on the number of products formed in the reaction, assuming a reaction at equilibrium.

Comment: This field is for additional comments such as reaction names (e.g. oxidative addition step, transmetallation step).

How to type in a second order reaction
       

Using the Hack Reaction model as an example, the input of a second order reaction is shown below:

 

 

You will see that once the reaction is entered and the Enter button is pressed, the reactants 4-bromobenzaldehyde and Pd_cat will be in the Reactants column and the product for the elementary reaction, Int_1, will be in the products column. When the reaction is created, you will see a slider bar in the forward rate column. This is used to increase/decrease the reaction rate. If you want to input your own value, click on the  icon on the right-hand side and this will show the kinetics parameters.

How to type in a reaction that is in equilibrium

There are two ways to do this:

1. You can type in a reaction separating the reactants and products with an equals (=) sign.

2. You can type in a forward reaction, and click in the reaction arrow to make it reversible. Clicking on the arrow again will make the reaction irreversible again.

Both cases are shown below using the Heck reaction model:

Use of pKa and pKb

If you would prefer to type in the pKa value rather than the equilibrium constant as it is more accessible (for example, the pKa of Acetic acid is 4.75). There is a dropdown menu located to the left of the equilibrium constant value. Clicking on this will bring you to a dropdown menu that contains pKa and pKb. Select pKa from this menu. Then type in the pKa value instead of the equilibrium constant.

 

How to check whether a reaction is balanced

If you want to find out if a reaction is mass balanced, go to the Bal column. If it is checked, then it is balanced. Similarly, if you want to check if the reaction is charge balance go to the [+/-] column if this is checked, it is charge balanced.

If either of these are not balanced you will see one of the following icons , the former means that the products side is lighter, and the latter is that the reactants side is lighter.

 

 

 


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