1. Optical Isomers: The mirror image of a species cannot be superimposed on the original structure. 2641

2. Optical Isomers: The mirror image of a species cannot be superimposed on the original structure. Review of some terminology 2642

3. Optical Isomers: The mirror image of a species cannot be superimposed on the original structure. Review of some terminology Chiral: Molecules or ions that have non- superimposable mirror images. 2643

4. Optical Isomers: The mirror image of a species cannot be superimposed on the original structure. Review of some terminology Chiral: Molecules or ions that have non- superimposable mirror images. Dextrorotatory: The optical isomer that rotates the plane of polarization to the right (as viewed towards the incoming beam). The isomer is labeled with a (+) and sometimes a d. 2644

5. Levorotatory: The optical isomer that rotates the plane of polarization to the left (as viewed towards the incoming beam). The isomer is labeled with a (-) and sometimes an l. 2645

6. Levorotatory: The optical isomer that rotates the plane of polarization to the left (as viewed towards the incoming beam). The isomer is labeled with a (-) and sometimes an l. Optically active: A compound with the ability to rotate the plane of polarized light. 2646

7. Levorotatory: The optical isomer that rotates the plane of polarization to the left (as viewed towards the incoming beam). The isomer is labeled with a (-) and sometimes an l. Optically active: A compound with the ability to rotate the plane of polarized light. Racemic mixture: A mixture of equal amounts of an optically active compound and its mirror image. 2647

8. Levorotatory: The optical isomer that rotates the plane of polarization to the left (as viewed towards the incoming beam). The isomer is labeled with a (-) and sometimes an l. Optically active: A compound with the ability to rotate the plane of polarized light. Racemic mixture: A mixture of equal amounts of an optically active compound and its mirror image. A racemic mixture will not rotate the plane of polarized light because the rotatory effects of the two isomers cancel each other. 2648

9. mirror plane [Zn(BrClFI)] 2- ion 2649

10. mirror plane [Zn(BrClFI)] 2- ion Cannot superimpose these two species; bromochlorofluoroiodozincate ion is chiral. 2650

11. 2651

12. 2652 cis-isomer: Structure I and the mirror image II are optical isomers. trans-isomer: There are no optical isomers for this complex ion.

13. Some Applications of Coordination Compounds 2653

14. Some Applications of Coordination Compounds Water treatment: Ca 2+ and Mg 2+ can be removed as a water soluble EDTA complex. P 3 O 10 5- is also used as a chelating agent for these ions. 2654

15. Some Applications of Coordination Compounds Water treatment: Ca 2+ and Mg 2+ can be removed as a water soluble EDTA complex. P 3 O 10 5- is also used as a chelating agent for these ions. 2655

16. Extraction of Metals: Gold and silver can be extracted as cyanide complexes with the ligand CN -. Ni can be purified using Ni(CO) 4 where CO is the ligand. 2656

17. Extraction of Metals: Gold and silver can be extracted as cyanide complexes with the ligand CN -. Ni can be purified using Ni(CO) 4 where CO is the ligand. Dyes: There are several dyes that are based on coordination compounds. 2657

18. Extraction of Metals: Gold and silver can be extracted as cyanide complexes with the ligand CN -. Ni can be purified using Ni(CO) 4 where CO is the ligand. Dyes: There are several dyes that are based on coordination compounds. Chemical analysis: There are a number of coordination compounds that are routinely used in chemical analysis. 2658

19. Dimethylglyoxime forms a red complex with Ni 2+ which is used both as a test for Ni 2+ and in gravimetric analysis for the determination of the amount of Ni in samples. 2659

20. Bonding in Coordination Compounds Crystal Field Theory 2660

21. Bonding in Coordination Compounds Crystal Field Theory Crystal field theory is an ionic model of bonding used for coordination compounds. 2661

22. Bonding in Coordination Compounds Crystal Field Theory Crystal field theory is an ionic model of bonding used for coordination compounds. This theory considers the bonding in complexes purely in terms of electrostatic interactions between the metal ion and the ligands. 2662

23. Bonding in Coordination Compounds Crystal Field Theory Crystal field theory is an ionic model of bonding used for coordination compounds. This theory considers the bonding in complexes purely in terms of electrostatic interactions between the metal ion and the ligands. All d-orbitals have the same energy in the absence of an external disturbance. 2663

24. The case of octahedral geometry 2664

25. If we place a metal ion in the center of an octahedron surrounded by six negative charges – two types of electrostatic interactions come into play: 2665

26. If we place a metal ion in the center of an octahedron surrounded by six negative charges – two types of electrostatic interactions come into play: 1. There is the attraction between the negatively charged ligands and the positive metal ion. 2666

27. If we place a metal ion in the center of an octahedron surrounded by six negative charges – two types of electrostatic interactions come into play: 1. There is the attraction between the negatively charged ligands and the positive metal ion. 2. There is electrostatic repulsion between the ligands and the electrons in the d orbitals. The magnitude of this repulsion depends on the particular d orbital. 2667

28. If we place a metal ion in the center of an octahedron surrounded by six negative charges – two types of electrostatic interactions come into play: 1. There is the attraction between the negatively charged ligands and the positive metal ion. 2. There is electrostatic repulsion between the ligands and the electrons in the d orbitals. The magnitude of this repulsion depends on the particular d orbital. For the orbital, the lobes point along the x and y axes, where the negative charges are placed. 2668

29. An electron residing in a orbital would experience a greater repulsion from the ligands than an electron in, say the d xy orbital. 2669

30. An electron residing in a orbital would experience a greater repulsion from the ligands than an electron in, say the d xy orbital. For this reason, is raised in energy (made less stable) while d xy, d xz, and d yz are lowered in energy. The is also raised in energy – because its lobes are pointed at the ligands along the z axis. 2670

31. Review 2671

32. 2672

33. As a result of metal ion-ligand interactions, the equivalence (in energy) of the five d orbitals is removed to give two high-lying levels: and of the same energy and three low-lying levels d xy, d yz, and d xz of the same energy. 2673

34. As a result of metal ion-ligand interactions, the equivalence (in energy) of the five d orbitals is removed to give two high-lying levels: and of the same energy and three low-lying levels d xy, d yz, and d xz of the same energy. The energy difference between these two sets of d orbitals is called the crystal field splitting. Its magnitude depends on the metal and the nature of the ligands. 2674

35. The best way to measure the crystal field splitting is by spectroscopic techniques (the absorption spectrum for example) where is the energy gap (crystal field splitting), h is Planck’s constant, h = 6.626 x 10 -34 Js, is the frequency of the photon, and is the wavelength. 2675

36. 2676

37. 2677 The absorption spectrum of Ti(H 2 O) 6 3+. The solution of this complex ion is purple.

38. By using a number of different ligands with the same metal ion the crystal field splitting can be measured and the spectrochemical series established. 2678

39. CO and CN - are called strong-field ligands because they cause a large splitting of the d orbitals. Cl - and Br - are weak-field ligands – they cause only a small splitting of the d orbitals. 2679

40. CO and CN - are called strong-field ligands because they cause a large splitting of the d orbitals. Cl - and Br - are weak-field ligands – they cause only a small splitting of the d orbitals. The magnitude of the crystal field splitting determines the magnetic properties of the complex. 2680

41. CO and CN - are called strong-field ligands because they cause a large splitting of the d orbitals. Cl - and Br - are weak-field ligands – they cause only a small splitting of the d orbitals. The magnitude of the crystal field splitting determines the magnetic properties of the complex. For Ti(H 2 O) 6 3+, the single d electron must be in one of the three lower orbitals and the ion is always paramagnetic. 2681

42. CO and CN - are called strong-field ligands because they cause a large splitting of the d orbitals. Cl - and Br - are weak-field ligands – they cause only a small splitting of the d orbitals. The magnitude of the crystal field splitting determines the magnetic properties of the complex. For Ti(H 2 O) 6 3+, the single d electron must be in one of the three lower orbitals and the ion is always paramagnetic. Paramagnetic: The tendency of a species with unpaired electrons to be attracted by an external magnetic field. 2682

43. When there are several d electrons different possibilities arise. Consider FeF 6 3- and Fe(CN) 6 3-. Each complex ion has 5 d electrons (for Fe 3+ ). 2683

44. According to Hund’s rule, maximum stability is reached when the five electrons enter five separate d orbitals with parallel spins. This arrangement requires an energy investment: in the presence of ligands, two of the five electrons must occupy the and the orbitals. Because F - is a weak- field ligand, that is, there is a small energy gap between the upper and lower d orbital energy levels, the five d electrons enter separate d orbitals with parallel spins to create a high-spin complex. 2684

45. On the other hand, CN - is a strong-field ligand, so it is energetically preferable to have all five electrons in the lower orbitals – and a low-spin complex is formed. 2685

46. 2686 FeF 6 3- Fe 3+ high spin The energy gap is small.

47. 2687 Fe(CN) 6 3- Fe 3+ Low spin The energy gap is large.

48. Exercise 1: Would you expect both of the complex ions CoI 6 3- and Co(CN) 6 3- to be paramagnetic? Exercise 2: Would you expect both of the complex ions Fe(H 2 O) 6 2+ and Fe(CN) 6 4- to be paramagnetic? 2688

49. The case of tetrahedral geometry The splitting pattern for the tetrahedral case is just the reverse of that for the octahedral complexes. In this case the d xy, d xz, and d yz orbitals are more closely directed at the ligands. 2689

50. 2690

51. The case of square planar geometry The splitting pattern for the square planar case is a bit more involved. You can think of the square planar case as arising from the octahedral case with the removal of the two ligands along the z axis. 2691

52. The case of square planar geometry The splitting pattern for the square planar case is a bit more involved. You can think of the square planar case as arising from the octahedral case with the removal of the two ligands along the z axis. With no z-axis interactions present, the orbital energy shows a significant decrease, and the d orbitals with a z component, d xz and d yz also decrease in energy (to the same extent). 2692

53. 2693

54. Sample problem: If the ions Al 3+, Zn 2+, and Co 2+ were placed in octahedral environments. Which can absorb visible light and thereby exhibit color? 2694

55. Sample problem: If the ions Al 3+, Zn 2+, and Co 2+ were placed in octahedral environments. Which can absorb visible light and thereby exhibit color? The electronic configuration of Al 3+ is 1s 2 2s 2 2p 6. Because it has no outer d electrons, electronic transitions will not occur in the visible, so it is colorless. 2695

56. Sample problem: If the ions Al 3+, Zn 2+, and Co 2+ were placed in octahedral environments. Which can absorb visible light and thereby exhibit color? The electronic configuration of Al 3+ is 1s 2 2s 2 2p 6. Because it has no outer d electrons, electronic transitions will not occur in the visible, so it is colorless. The Zn 2+ ion has the electronic configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10. In this case the 3d orbitals are filled. There is no room for the or orbitals to accept an electron from a lower d xy, d xz or d yz orbital. The complex is therefore colorless. 2696

57. The Co 2+ ion has the electronic configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 7. In this case there is room for the movement of a d electron from one of the lower energy d xy, d xz, or d yz orbitals, into the higher energy or orbitals. 2697

58. The Co 2+ ion has the electronic configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 7. In this case there is room for the movement of a d electron from one of the lower energy d xy, d xz, or d yz orbitals, into the higher energy or orbitals. The complex is therefore expected to be colored, and that is experimentally observed. 2698

59. THE END Time for review 2699

60. Summary of Key Problem Types Thermochemistry/Thermodynamics 1. Calculation of enthalpy changes: a. Heat of reaction b. Heat of formation c. Enthalpy change for a phase transition d. Enthalpy of combustion e. Heat of solution 2700

61. 2. Hess’ Law problems. 3.Calorimetry calculations: Determine the enthalpy change for a process from a measured temperature change. 4.Calculations using the First Law of Thermodynamics – involving work, heat, and internal energy. 5. Calculation of entropy changes from standard entropy values. 2701

62. 6. Calculation of the Gibbs energy from enthalpy and entropy changes (at a given temperature). 7. Analysis of the equation to determine when a reaction will be spontaneous. Conditions for a reaction to be spontaneous. 8. Equilibrium calculations involving, e.g. determine the enthalpy change, the temperature, or the entropy change for a phase transition given two of these variables. 2702

63. Kinetics Kinetics 9. Approximate calculation of the rate of reaction given the time interval and the change in concentration of a species. 10. Determination of an accurate rate using the slope method from a concentration vs. time plot. 11. Calculation of the reactant order in a rate law expression. 2703

64. 12. Calculations of concentrations, rate constants, half-lives for zero-order and first-order reactions. Calculation of time required for a certain concentration to be reached (radioactive method to date objects). 13. Calculation of the rate constant from a plot of ln([A] 0 /[A] t ) vs. time (for first-order reactions). 2704

65. 14. Calculations using the Arrhenius equation: a. Determination of E a b. Determination of k c. Determination of T d. Graphical methods 15. Writing rate law expression from elementary steps. 2705

66. Chemical equilibria – general 16. Writing expressions for equilibrium constants and reaction quotients for chemical reactions involving solids, liquids, and gases. 17. Use of the ideal gas equation PV = nRT to go from K c to K p or from K p to K c. 18. Multiple equilibria – product of the equilibrium constants gives the overall equilibrium constant for the combined reaction. 2706

67. 19. Calculation of the equilibrium concentrations given K and the initial concentrations. (ICE table problems). a. Approximate solution approach. b. Quadratic equation approach. 20. Problems involving LeChatelier’s principle. a. Concentration changes b. Temperature changes c. Pressure changes 2707

68. 21. Calculation of away from equilibrium. 22. Calculation of K given, or the calculation of given K. 23. Solubility product calculations a. Calculation of K sp. b. Calculation of solubility. c. Common ion effect calculations. d. Calculation of when precipitation will occur. e. Simple approximations to employ. 2708

69. Acid-Base Equilibria 24. pH Calculations. a. Strong acids, b. strong bases, c. weak acids, d. weak bases, e. mixtures of acids + bases. 25. Equilibrium calculations involving K a and K b. Calculation of per cent dissociation. 26. Equilibrium calculations involving polyprotic acids – simple approximations to employ. 2709

70. 27. Salt hydrolysis – calculation of the pH of salt solutions. 28. Buffer calculations using the Henderson- Hasselbalch equation. 2710

71. Electrochemistry 29. Balancing redox equations. 30. Faraday’s law calculations: a. Calculation of moles of product or reactant. b. Calculation of time or current to produce required amount of product. 2711

72. 31. Calculation of standard emf for redox reaction. 32. Calculation of from E 0. 33. Calculation of K from E 0. 34. Calculation of maximum (non-expansion) work for a cell. 35. Prediction of spontaneous direction for a redox reaction. 2712

73. 36. Calculations involving the Nernst equation. 2713