[maydengar]

I'm doing some some undergraduate research. Are there any resources that explain how to properly draw up a reagents table, based on an experimental? Does the amount of solvent follow the stoichiometric equivalence of the starting reagents? how much reagent do you actually need if it says 'in excess'?

[Uberbane]

I don't think there are any sources per say how to set up a reagent table. But I generally include the following when setting up a reagents table based on an experimental.

1) The reagent number (as you should draw up that particular step in the reaction and number each reagent)
2) Its molar mass
3) What physical state the reagent is
4*) The mass you're using in the reaction & how many moles that mass corresponds to
5*) Concentration of the reagent, its volume, and density
6) Relevant safety information - exposure routes and hazards per MSDS sheets

* If necessary


If you're following experimentals, I would just adjust the amount of solvent based on what ratio you're performing the experiment at in relation with those used in the experimental. As a general rule of thumb, though, you should use the minimum amount of solvent that it takes to fully dissolve your starting materials.

"In excess" is up to debate, but I've generally taken it to mean 1.2 to 1.5 equivalents of the limiting reagent, but it largely depends on what type of reaction you're completing and the conditions under which you're doing the reaction. You should be able to calculate the amount of equivalents that were used based on an experimental, as well.

Hope that helps.

[maydengar]

If you're following experimentals, I would just adjust the amount of solvent based on what ratio you're performing the experiment at in relation with those used in the experimental. As a general rule of thumb, though, you should use the minimum amount of solvent that it takes to fully dissolve your starting materials.

okay thanks! so if the experimental says 40g reagent and I'm using only 1g, I can just divide all the other reagents and solvents by 40, unless the reaction doesn't dissolve, in which case I'd just add more solvent, right?

[kriggy]

Yeah thats how I would do it. I wouldnt add any solvent unless its necessary, its good idea to follow the procedure exactly as it says on the first trial. Sometimes it might be weird because you will be dissolving in crazy low or high amounts of solvent but I learned the hard way so you dont have to