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precursor chemicals
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sciencelogic:
In general, there mustn't be any problem If we multiply the listed precursor chemicals of a reaction for achieving more yield, right?
MNIO:
what do you mean?
let's use this for an example
1 C7H6O3 + 1 C4H6O3 ---> 1 C9H8O4 + 1 CH3CO2H
from the stoichiometry, we can see that
138g salicylic acid + 102g acetic anhydride ---> 180g aspirin + 60g acetic acid
so the theoretical yield of aspirin if we react
salicylic acid acetic anhydride theoretical yield aspirin
138g 102g 180g
276g 102g 180g
138g 204g 180g
276g 204g 360g
Those are theoretical yields. Actual yield (amount you actually produce and recover)
will be less. The % yield (actual / theoretical x 100%) varies as you vary process
conditions. Things like reactor design (shape, mixing, residence time, amounts,
concentrations, temp, pressure, etc) are all important factors to consider. Things like
separation/purification/recovery processes all have an impact on actual yield. I'll go out
on a limb here and say for "any particular fixed process", there is an optimum amount of
reactants that maximize actual and % yields. Meaning, I would hesitate to simply
double amounts of reactants and count on doubling the product yield without properly
"scaling up" the process.
So.. IF you mean
(1) in general chemistry class, can I double the amounts of reactants to double products?
and the answer is yes, if you are careful to consider limiting reagents
(2) in real life production, can I double amounts of reactants and expect to double
amounts of final products? NO. Not without slight to major modifications of your process.
sciencelogic:
--- Quote from: MNIO on April 05, 2020, 08:52:49 PM ---what do you mean?
let's use this for an example
1 C7H6O3 + 1 C4H6O3 ---> 1 C9H8O4 + 1 CH3CO2H
from the stoichiometry, we can see that
138g salicylic acid + 102g acetic anhydride ---> 180g aspirin + 60g acetic acid
so the theoretical yield of aspirin if we react
salicylic acid acetic anhydride theoretical yield aspirin
138g 102g 180g
276g 102g 180g
138g 204g 180g
276g 204g 360g
Those are theoretical yields. Actual yield (amount you actually produce and recover)
will be less. The % yield (actual / theoretical x 100%) varies as you vary process
conditions. Things like reactor design (shape, mixing, residence time, amounts,
concentrations, temp, pressure, etc) are all important factors to consider. Things like
separation/purification/recovery processes all have an impact on actual yield. I'll go out
on a limb here and say for "any particular fixed process", there is an optimum amount of
reactants that maximize actual and % yields. Meaning, I would hesitate to simply
double amounts of reactants and count on doubling the product yield without properly
"scaling up" the process.
So.. IF you mean
(1) in general chemistry class, can I double the amounts of reactants to double products?
and the answer is yes, if you are careful to consider limiting reagents
(2) in real life production, can I double amounts of reactants and expect to double
amounts of final products? NO. Not without slight to major modifications of your process.
--- End quote ---
Thanks,
that's exactly what i'm looking for. sorry that my question is really naive. I'm a newbie in chemistry.
so as you said, these are all correct. right?
salicylic acid acetic anhydride theoretical yield aspirin
1 x 138g 102g 180g
2 x 276g 204g 360g
5 x 690g 510g 900g
10x 1380g 1020g 1800g
MNIO:
yes those are all correct.. "theoretical yields". make sure you watch the stoichiometric ratios. And again, your actual yields will be less than theoretical yields and approximately scaleable.. usually.
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