Hawler Medical University Department of Pharmaceutical chemistry Presented by pharmacist Omar Abdulrahman M.Sc. Pharmaceutical chemistry Hawler Medical University College of Pharmacy Department of Pharmaceutical chemistry

Medicinal Chemistry Definition Definition: Medicinal chemistry, also known as Pharmaceutical chemistry is an interdisciplinary science concerned with the design, development and synthesis of pharmaceutical or bio-active molecules. The discipline combines expertise from chemistry and pharmacology to identify, develop and synthesise chemical agents that have a therapeutic use and to evaluate the properties of existing drugs.

Mass and Moles of a Substance Chemistry requires a method for determining the numbers of molecules in a given mass of a substance. The molecular weight of a substance is the sum of the atomic weights of all the atoms in a molecule of the substance.

Mass and Moles of a Substance The Mole Concept: A mole is defined as the quantity of a given substance that contains as many molecules or formula units as the number of atoms in exactly 12 grams of carbon–12. 1-octanol Mercury(II) Iodide The number of atoms in a 12-gram sample of carbon–12 is called Avogadro’s number (to which we give the symbol Na). The value of Avogadro’s number is 6.02 x 1023. Sulfur Methanol

Mass and Moles of a Substance Mole calculations: Suppose we have 100.0 grams of iron (Fe). The atomic weight of iron is 55.8 g/mol. How many moles of iron does this represent?

Mass and Moles of a Substance Mole calculations: suppose we have 5.75 moles of magnesium (atomic wt. = 24.3 g/mol). What is its mass? Or 1.40 x 102 grams of Mg

Concentration of Solutions Molarity (M), or molar concentration, is a measure of the concentration of a solute in a solution, or of any chemical species, in terms of amount of substance in a given volume. is defined as the number of moles of solute per liter of solution. Other common rearrangements:

Concentration of Solutions Normality Definition Normality is a measure of concentration equal to the gram equivalent weight per liter of solution. Gram equivalent weight is the measure of the reactive capacity of a molecule. The solute's role in the reaction determines the solution's normality. Normality is also known as the equivalent concentration of a solution. N = molarity x equivalents

equiv.wt of H2SO4 = M.wt H2SO4 / 2 = 98/2 = 49 g/equiv equiv.wt of an acid = M.wt / no. of replaceable H+ Example: equiv.wt of H2SO4 = M.wt H2SO4 / 2 = 98/2 = 49 g/equiv equiv.wt of H3PO4= M.wt H3PO4 / 3 = 32.67 g/equiv Example Problem Find the normality of 0.1 M H2SO4 (sulfuric acid) for the reaction: H2SO4 + 2 NaOH → Na2SO4 + 2 H2O According to the equation, 2 moles of H+ ions (2 equivalents) from sulfuric acid react with sodium hydroxide (NaOH) to form sodium sulfate (Na2SO4) and water. Using the equation: N = molarity x equivalents N = 0.1 x 2 N = 0.2 N

Potential Issues Using N for Concentration Although normality is a useful unit of concentration, it can't be used for all situations because its value depends on an equivalence factor that can change based on the type of chemical reaction of interest. As an example, a solution of magnesium chloride (MgCl2) may be 1 N for the Mg2+ ion, yet 2 N for the Cl- ion. While N is a good unit to know, it's not used as much as molarity or molality in actual labwork.

How would you prepare 60.0 mL of 0.2 M HNO3 from a stock solution of 4.00 M HNO3? M1V1 = M2V2 V1 = M2V2 M1 = 0.200 x 0.06 4.00 =3 mL 3 mL of acid +57 mL of water =60 mL of solution

Another Dilution Problem If 32 mL stock solution of 6.5 M H2SO4 is diluted to a volume of 500 mL What would be the resulting concentration? M1*V1 = M2*V2 (6.5M) * (32 mL) = M2 * 500.0 mL 6.5 M * 32 mL M2 = 500 mL M2 = 0.42 M

Example : Prepare 0.1 M of NaCl in 250 ml of Water ? Wt= M x M.wt. x V(ml) / 1000 = 0.1 x 55.5 x 250 / 1000 = 1.3875 g

Molarity(M) of acid= [sp.gr x % x 1000] / M.wt. Example: Calculate the Molarity(M) of HNO3 M.wt=63g/mole , sp.gr =1.42 , %w/w=70 Molarity(M) of HNO3 = (1.42x0.70x1000)/63=16 M.

Example: Calculate the volume required to prepare 100 ml of HCl 6.0M . 37%w/w, sp.gr =1.18 and M.wt HCl = 36.5 MHCl=(1.18 x 0.37 x 1000) / 36.5 = 12 mol/l=12M Vconc. x Mconc. =Vdil. xMdil. Vconc x 12 =100 x 6.00 Vconc = 50 ml

Theoretical and Percentage of Yield The theoretical yield of product is the maximum amount of product that can be obtained from given amounts of reactants. The percentage yield is the actual yield (experimentally determined)