How to calculate theoretical yield if there are minor products?

Calculating theoretical yield for a reaction with a single product is pretty trivial: Multiply the amount of moles of limiting reagent to the molar ratio of the limiting reagent and product to the molecular weight of the product.


However, if the reaction is also capable of producing side product, this method no longer works because some portion of that limiting reagent would be used to create the minor product. Therefore, the ONLY way to calculate theoretical yield for a reaction with multiple products would be to know the ratio between them. In other words, if the ratio of major to minor product is unknown, then it would be impossible to calculate theoretical yield for that reaction. Is this correct?


We can use an example to illustrate this. Take 1-methyl,1-bromo-cyclohexane. When mixed with a strong base, we get two E1 products, a major trisubstituted alkene and minor disubstituted alkene. In order to calculate the theoretical yield of the major product, we would have to know its molar ratio to the minor product?
If I did know the ratio, was lets say, 80 to 20. All I would have to do is multiply the mass of the limiting reagent by 0.8 because only 80% of the mass would be used to create major product?


Thanks!


