Everything about Yield Chemistry totally explained
In
chemistry,
yield, also referred to as
chemical yield and
reaction yield, is the
amount of
product obtained in a
chemical reaction. The
absolute yield can be given as the weight in
grams or in
moles (
molar yield). The
fractional yield or
relative yield, which serve to measure the effectiveness of a synthetic procedure, is calculated by dividing the amount of the obtained product in moles by the
theoretical yield in moles:
To obtain the
percentage yield, multiply the fractional yield by 100% (for example, 0.673 = 67.3%).
One or more reactants in a chemical reaction are often used in excess. The theoretical yield is therefore calculated based on the molar amount of the
limiting reactant, taking into account the
stoichiometry of the reaction. For the calculation it's usually assumed that there's only one reaction involved.
The ideal or
theoretical yield of a chemical reaction would be 100%, a value that's impossible to achieve in a practical setting. According to Vogel's Textbook of Practical Organic Chemistry, yields around 100% are called
quantitative, yields above about 90% are called
excellent, yields above about 80%
very good, yields above about 70% are called
good, yields below about 50% are called
fair, yields below about 40% are called
poor.
Yields may appear to be above 100% when products are impure. Purification steps always lower the yield and the reported yields usually refer to the yield of the final purified product.
Further Information
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