Illustrated Glossary of Organic Chemistry

Yield (reaction yield): A measure of a chemical reaction's efficiency, as a ratio of moles of product to moles of reactant. Usually expressed as a percentage.

% Yield =

Moles of product -------------------- Moles of reactant

General form of the equation used to compute reaction yield.

	CH3Cl	+	NaI		CH3I	+	NaCl
Molar  mass	50.49 g mol-1		149.89 g mol-1		141.94 g mol-1		58.44 g mol-1
Grams used	10.0 grams		10.0 grams		-----		----
Moles used	0.198 mole		0.0667 mole		----		----
Grams produced	----		----		5.81 grams		3.80 grams
Moles produced	-----		----		0.0409 mole		0.0653 mole

In this S_N2 reaction, the yield of CH₃I (A reaction product) from CH₃Cl (a reactant) is (moles CH₃I/moles CH₃Cl) x 100% = (0.0409 mole/0.198 mole) x 100% = 20.7%. Maximum theoretical yield is 100%, so this is not a very efficient reaction.