MNU Pharmaceutical Analytical Chemistry Lecture Notes PDF

(PA 101)-Pharm D-Clinical Pharmaceutical Analytical Chemistry-I  Lecture 1 Complex formation titration 2 At the end of the lecture the students will be able to understand: Complex; definition. Ligands and Chelating agents; classification. Complex ions...

(PA 101)-Pharm D-Clinical Pharmaceutical Analytical Chemistry-I  Lecture 1 Complex formation titration 2 At the end of the lecture the students will be able to understand: Complex; definition. Ligands and Chelating agents; classification. Complex ions; stability / geometry. Factors affecting Stability of Complex 4 Interactive teaching methods Checkpoints of Classroom discussion External video resources: Calcium-EDTA titration https://www.youtube.com/watch?v=hTy9JBllUVg Titration of water hardness (complexometry explained). https://www.youtube.com/watch?v=akRcLMQUxm4  A species formed by the association of two or more simpler species; each capable of independent existence. A + Ag B NH3 Complex Ag(NH3)2+ 6 When one of the species is a metal ion; the resulting entity is called a. e- donor Atoms Metal ion Ligand (Mn+) (: L) or (L -) Groups e- acceptor Neutral (lone electrons pairs), HA = H+ + A- e.g., :NH3, :NH2R, H2Ӧ: ….etc. Conjugate base of an acid, e.g., Cl- , CN-, SCN-….etc. Metal Complex 7  Complex formation reaction is a type of acid-base reaction according to Lewis concept where the metal ion is a Lewis acid (electron acceptor), while the ligand is the Lewis base (electron donor). Acid-base reaction Complex Mn+ + :L [ML]n+ Formation Metal ligand complex reaction 8  (-) → anion n (+)→cation Ligand (0)→neutral The charge carried by the complex ion is the Metal Ligand Ligand ion algebraic sum of the charges on the central No. of atoms or groups Complex inion which one attached and the (ligands) of the Ligand species is a occupying Arranged ligands.in a a central definite position, surrounded by a geometrical fixed No.patternof about the central metal ion which are arranged in a fixed geometrical pattern. 9 Characteristic A metal can have for > one coordination number each metal (2, 4, 6) Coordination number Number of ligands that are bound to each metal ion Ag+ + 2:NH3 = [Ag(NH3)2]+ 10 Hexamminecobalt (III) ion Tetrachloroplatinate (II) ion 11  Types of ligands Ligands Simple Chelating (Unidentate, (Multidentate) monodentate) 12 Hexamminecobalt (III) ion Tetrachloroplatinate (II) ion 13 ONE site of attachment to the metal ion Examples H2O :NH3 CN- Cl- Product: METAL COMPLEX 14 Heterocyclic ring (chelating ring) 15  Heterocyclic ring (chelating ring) Glycine aminoacid Bis (glycinato) copper (II) 16  Chelating Ligand > ONE site of attachment to the metal ion forming heterocyclic ring (chelating ring) Classification (No. attachment sites) Bidentate Tridentate Tetradentate Hexadentate Product: METAL CHELATE 17  Organic molecules containing arranged in a manner to give a (chelate ring) where the metal is a member of this ring. 18 Chelate ring Heterocyclic ring that is formed when a chelating ligand is attached to metal ion by more than one site. Chelating agent Molecule or anion that forms a chelate ring with metal ions. Chelation The process of forming a chelate ring. Metal chelate Metal complex in which metal is bonded by coordinate bond to non-metallic elements of Groups V and VI. Organometallics Organic compounds in which metal is covalently bonded to carbon. 19 Classification of chelating agents Attachment sites Bidentate Tridentate Tetradentate (quadridentate) 6? 20.. O OH H2C NH2 O O– CH H2C..NH2 R1..NH2 O– O Ethylene diamine Amino acid oxalate (en) (AA) O-phenanthroline (1,10- phenanthroline) N N 21 H2N.. NH.. NH2.. Diethylenetriamine 22  N NH HN H N N NH2 H2N H N Triethylenetetramine (Trien) Porphyrin = Porphin 23 Ethylenediamine tetraceic acid (EDTA) 24 It is not necessary that a polydentate ligand should always use all its donor atoms for the coordination purposes. 25  EDTA Co2+ Cu2+ and Zn2+ (Coordination No. = 6) (Coordination No.= 4 ) EDTA is EDTA is hexadentate quadridentate 26 2 acidic groups 2 basic groups 1 acid group + 1 basic group 27 = C-OH phenolic =NH Imino -COOH Carboxylic =N-OH Oximino -SO2H Sulfenic -SO3H Sulfonic 28 C=O Carbonyl -OH Hydroxyl -O- Ether -NH2 Amino -SO2- Sulfone Cyclic N -NO Nitroso 29 o1- Properties of the central metal ion. o2- Properties of the ligand. o3- Stability of chelate. 30 o 1- Properties of the central metal ion. Transition metals Type Mn, Fe, Co, Ni, Cu, Zn ↑attraction to :L →↑stability ↑Charge → ↑stability Charge ( Fe3+ > Fe2+ ) Ionic radius ↓ radius → ↑ Charge → ↑stability 31 ↑ionic potential → ↑stability 32 o2- Properties of the ligand: Basic character ↑ Basicity →↑stability of the donating e.g., (N, O, S) atom ↑ radius → ↑stability Radius I- > Br- >Cl- >F- 34 o 3- Stability of chelate: Type Chelated > non-chelated (complex) Size 5, 6 membered > 4 (chelate ring) No. rings/ligand ↑No. rings→ ↑stability No. rings Ligand 35  Chelate Effect When the No. of Chelated chelate rings per complexes are ligand increases, more stable than the stability of the non-chelated complex increases. complexes 36 Titrant Complex NH3 [Cu(NH3)4]2+ ---- Trien ____ 37 Cu2+ + NH3 ⇌ [Cu (NH3)]2+ [Cu (NH3)]2+ + NH3 ⇌ [Cu (NH3)2]2+ [Cu (NH3)2]2+ + NH3 ⇌ [Cu (NH3)3]2+ [Cu (NH3)3]2+ + NH3 ⇌ [Cu (NH3)4]2+ 38  Nuclearity of complex? Metal chelate that contains two or more central metal atoms; in which the chelating ligand acts as a coordinating bridges. 2+ N Ag N N Ag N Ethylenediamine : Ag+ Dithiooxamide (rubeanic acid) : Cu2+ 39 40 41  EDTA is ……………………… a) hexadentate ligand b) tetraprotic acid c) may act as quadridentate ligand d) All are correct Answer: d Complexone (III) – (Na2H2Y. 2H2O) act as a) Electron donating ions b) Electron accepting ions c) Both electron doanting & accepting ions d) None of them Answer: a Which sentence is false about ligand? a) It is act like Lewis base b) CN¯ is example of unidentate. c) It is electron donor group. d) EDTA is example of unidentate. Answer: d 42  Triethylene tetramine is an example of: a) Bidentate Ligands. b) Tridentate Ligands. c) Tetradentate Ligands. d) Hexadentate Ligands. Answer: c Complexometric titrations are useful for the determination of a) Non-metal ions b) Basic drug c) Metal ions d) None of them Answer: c 43 Short essay questions Factors affecting the stability of complex ion with examples? Define Coordination number The least requirements for a chelating agent 44  References  Qualitative Chemical Analysis, Daniel C. Harris, 10th ed., W.H. Freeman and Company, New York (2022).  Fundamentals of Analytical Chemistry by Douglas A. Skoog, Stanley R. Crouch, F. James Holler, Donald M. West Hardcover, Published by Cengage Learning, Inc, United States (2021).