theoretical yield

Examples of theoretical yield in the following topics:

• Calculating Theoretical and Percent Yield

  • It is the ratio between the actual yield and the theoretical yield.
  • This number can be calculated and is called the theoretical yield.
  • To evaluate the efficiency of the reaction, chemists compare the theoretical and actual yields by calculating the percent yield of a reaction:
  • Then the theoretical yield of the product can be determined and, finally, compared to the actual yield.
  • Calculate the percent yield of a reaction, distinguishing from theoretical and actual yield.

• The Acid Dissociation Constant

  • Smaller Ka values yield larger pKa values.
  • Acids with a pKa value of less than about -2 are said to be strong acids; a strong acid is almost completely dissociated in aqueous solution, to the extent that the concentration of the undissociated acid becomes undetectable, which makes experimental calculations difficult. pKa values for strong acids can, however, be estimated by theoretical means or by extrapolating from measurements in non-aqueous solvents in which the dissociation constant is smaller, such as acetonitrile and dimethylsulfoxide.

• Photochemistry

  • The efficiency with which a given photochemical process occurs is given by its Quantum Yield (Φ).
  • Since many photochemical reactions are complex, and may compete with unproductive energy loss, the quantum yield is usually specified for a particular event.
  • Thus, we may define quantum yield as "the number of moles of a stated reactant disappearing, or the number of moles of a stated product produced, per einstein of monochromatic light absorbed
  • The quantum yield of these products is less than 0.2, indicating there are radiative (fluorescence & phosphorescence) and non-radiative return pathways (green arrow).
  • Several secondary radical reactions then follow (shown in the gray box), making it difficult to assign a quantum yield to the primary reaction.

• Salts that Produce Basic Solutions

  • When dissolved in water, a basic salt yields a solution with pH greater than 7.0.
  • Because it is capable of deprotonating water and yielding a basic solution, sodium bicarbonate is a basic salt.
  • Because the bicarbonate ion is the conjugate base of carbonic acid, a weak acid, sodium bicarbonate will yield a basic solution in water.

• The Henderson-Hasselbalch Equation

  • The Henderson–Hasselbalch equation connects the measurable value of the pH of a solution with the theoretical value pKa.

• Writing Chemical Equations

  • A chemical equation expresses a chemical reaction by showing how certain reactants yield certain products.
  • The two are separated by an arrow symbol ("→" usually read aloud as "yields").
  • This equation would be read as "CH four plus two O two yields CO two and two H two O."
  • Using IUPAC nomenclature, this equation would be read as "methane plus oxygen yields carbon dioxide and water."

• Total Synthesis

  • If a 95% yield can be achieved with each step, an eight-step synthesis affords a net yield of 66% (0.958*100%).
  • Assuming 95% yield for each step, each of W, X, Y and Z are produced from starting materials in 95% yield.
  • Combining them sequentially requires three steps (W+X, then add Y, then Z), which results in an 86% yield (0.953*100%).
  • Once the ester is reduced, the acetal can be removed, thus yielding the original ketone functionality.
  • Protecting groups can be extremely useful, but to be worthwhile, must use inexpensive materials and must be easily added and removed in high yield.

• Occurrence of Aldehydes and Ketones

  • When chiral compounds are found in nature they are usually enantiomerically pure, although different sources may yield different enantiomers.

• Strong Bases

  • Strong bases either dissociate completely in solution to yield hydroxide ions, or deprotonate water to yield hydroxide ions.

• The Integrated Rate Law

  • When the integrated rate law is written in this way, a plot of $ln[A]$ versus t will yield a straight line with the slope -k.
  • Here, a plot of $\frac{1}{[A]}$ versus t will yield a straight line with a positive slope k.
  • In this more complicated instance, a plot of $ln\frac{[B][A]_0}{[A][B]_0}$ versus t will yield a straight line with a slope of $k([B]_0-[A]_0)$.
  • Note here that a plot of [A] versus t will yield a straight line with the slope -k.
  • A summary of the various integrated rate laws, including the different plots that will yield straight lines, can be used as a resource.