![]() ![]() Thus 81% of the theoretical yield is actually isolated, which is a very respectable yield, that would please most chemists. Assuming that the actual yield is 1.20 g calculation of the % yield is as follows. ![]() This reaction typically produces actual yields of 1-1.2 g. In fact no reaction ever proceeds with 100% yield due to such factors as the formation of side products, incomplete conversion of the starting materials, loss upon workup of the reaction mixture, and loss upon isolation and purification of the desired product. Theoretical yield = (moles of limiting reagent)(stoichiometric ratio desired product /limiting reagent)(MW of desired product) = (moles of 1-butanol)(stoichiometric ratio 1-bromobutane/1-butanol)(MW of 1-bromobutane) =(0.0180 mole)(1 mole / 1 mole)(137.03 g/mole) =1.48 gĪbove quantities of reagents the maximum amount (assuming 100% yield) of 1-bromobutane that can be produced is 1.48 g. Calculation of the (as shown below) theoretical yield of 1-bromobutane gives 1.48 g. ![]() From the stoichiometry of the reaction (Equation 1a) it is clear that one mole of each reactant is required to produce one mole of product (1-bromobutane) and since 1-butanol (0.0108 mole) is used in the smallest amount it is the limiting reagent. Dividing the weight of each reactant that is used, by the molecular weight of the reactant, gives the number of moles of each reagent used. The following Reagents Table (Table 1) and Desired Product Table (Table 2) can then be A typical procedure 1 for this reaction begins with dissolvingĮquation 1a 1.33 g of sodium bromide (2) in 1.5 mL of water, followed by addition of 0.80 mL of 1-butanol (1) and 1.1 mL (2.0 g) of concentrated sulfuric acid (3). In order to illustrate the calculation of the percentage yield (and the measurement of the efficiency of a reaction) consider the following acid promoted nucleophilic substitution reaction. Percentage yield= (actual yield/theoretical yield) X 100 Theoretical yield = (moles of limiting reagent)(stoichiometric ratio desired product/limiting reagent)(MW of desired product) In general organic chemists consider yields of 90% or better as excellent while 20% or less are poor. Students are often required, especially in laboratory, to determine the theoretical yield based upon the limiting reagent and then to calculate the percentage yield based upon the ratio of the actual yield/theoretical yield X 100. Cann, Chemistry Department, University of Scranton Efficiency of a ReactionĪlthough the efficiency of a reaction can be measured in many ways, by far the most common way is to calculate the yield (percentage yield). Suggested Use: An organic chemistry course (both lecture and lab) during a discussion of various reactions (substitution, elimination, addition, rearrangements, etc.)ĪTOM ECONOMY: A Measure of the Efficiency of a Reaction ![]()
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