# Theoretical yield calculation

[COLOR="#008000"]Dear forum,

I have small doubt regarding calculation of theoretical yield.
For ex X + Y = Z (Both X & Y are KSMs)
say
Mol.wt of ‘X’ = 100,
Mol.Wt of ‘Y’ = 200
Mol.wt of ‘Z’ = 150

then which KSM should i consider for calculating the theoretical for that particular step step???
I think we have to consider, which KSM leads to produce less quantity of product.
i mean to say that, which molecular wt is high then theoretically that reactant leads to less yield… based on this fin the above Ex answer is 'Y’
is it correct?? Kindly suggest and provide if any literature is available for the same.

Regards
svr[/color]

Dear SVR…

Theoretical yield of “Z” = Input quantity of KSM x Mol Wt. of “Z” / Mol. Wt. of KSM

If your raw-material quantities are correctly given by your development team, then no question of KSM. You can consider either “X” of “Y” is KSM. For better clarification, please see below example. We are manufacturing Itraconazole and “Itra A” and “Itra B” are two input materials

Itra A: Mol wt (393.5), quantity usedin reaction (125.0 kg)
Itra B: Mol wt (408.0), quantity usedin reaction (129.5 kg)
Itraconazole: Mol wt (706)
If “Itra A” is considered as KSM, then theoriticla yield = 125 x 706 / 393.5 = 224 kg (from above formula)
If “Itra B” is considered as KSM, then theoriticla yield = 129.5 x 706 / 408 = 224 kg

But, if your development team considered “X” as KSM and calculated the quantity of “Y” (by adding some overages for optimization of reaction), then you have to consider only “X” as KSM. Better you consult your R&D head. He may provide you best solution.

In some reactions… 1 mol of “X” + 1 mol of “Y” = 2 moles of “Z”. Then you have to double your theoretical yield (obtained using above formula) to get the actual theoretical yield

Regards
Veerraju