Chemistry 201 Final Exam 1

Transcription

1 Lecture Slides Booklet Solutions Test Solutions Extra notes and advice Advice on which exams and questions to write Corrections Available December 15 th at: Chemistry 201 Final Exam 1 Friday, April 14 11:00 to 12:30 Molecular Orbital Theory 12:30 to 13:00 Break 13:00 to 14:15 Functional Groups through VSEPR 14:15 to 14:30 Break 14:30 to 16:00 Hybridization and VSEPR Saturday, April 15 Questions? Suggestions? me and I will try to find time to reply. psedach@learnfaster.ca All the best! 11:00 to 12:30 Intermolecular Forces in Detail 12:30 to 13:00 Break 13:00 to 14:15 Isomers and Review 14:15 to 14:30 Break 14:30 to 16:00 Review

2 Molecular Orbital Theory 2 Hybridization vs. Molecular Orbitals (VSEPR)

3 MO Theory Linear Combination of Atomic Orbitals (LCAO) is 3 simply Molecular Orbital Theory for two atoms F F 2p 2p Energy 2s 2s 1s 1s

4 MO Theory *we assume here that our bond forms along the x-axis 4 2p 2p B.O.= Energy 2s 2s F F

5 MO Theory *we assume here that our bond forms along the x-axis 5 ABMO Anti-Bonding Molecular Orbital 2s 2s Energy 2s 2s NBMO Non-Bonding Molecular Orbital 2s 2s F F BMO Bonding Molecular Orbital

6 MOs of 6 -bonding interaction Energy 2p 2p -bonding interaction F F

7 MO Theory 7 F F F F 2p 2p Energy 2s 2s

8 MO Theory 8 F F F F 2p 2p Energy 2s 2s

9 MO Theory along z-axis 9 2p O O 2p VSEPR Predicts O O Energy MO Theory Predicts O O 2s 2s

10 MO Theory along y-axis 10 VSEPR Predicts N O N O 2p 2p MO Theory Predicts Energy N O 2s 2s

11 MO Theory along y-axis 11 VSEPR Predicts F O F O 2p 2p MO Theory Predicts Energy F O 2s 2s

12 MO Exceptions Homonuclear Diatomics and smaller along x-axis 12 N N VSEPR Predicts 2p 2p MO Theory Predicts N N Energy All exceptions: 2s 2s Literally every homonucelar diatomic smaller and including.

13 MO Theory Does exist? 13 B B VSEPR Predicts 2p 2p MO Theory Predicts B B Energy All exceptions: 2s 2s Literally every homonucelar diatomic smaller and including.

14 14 VSEPR or Valence Bond Theory

15 Intramolecular Bonding 15 The type of bond a compound forms is based on electronegativity Electronegativity is a measure of how much an atom attracts electrons in the bond in molecule Covalent Bonding Ionic Bonding homonuclear diatomics electron sharing electron transfer dipole moment Covalent

16 / E Shape: linear M Shape: linear / / E Shape: tetrahedral or Td M Shape: tetrahedral or Td / / E: trigonal bipyramidal M: trigonal bipyramidal / VSEPR Summary / E: Octahedral (Oh) M: Octahedral (Oh) / 16 E Shape: trigonal planar M Shape: trigonal planar / E Shape: tetrahedral or Td M Shape: trigonal pyramidal / E: trigonal bipyramidal M: see-saw / / E: Octahedral (Oh) M: Square Pyramidal / E Shape: trigonal planar M Shape: bent, < 120 E Shape: tetrahedral or Td M Shape: bent, < E: trigonal bipyramidal M: T-shaped E: trigonal bipyramidal M: linear E: Octahedral (Oh) M: Square Planar Pavel Sedach

17 Systematic Lewis Structures 17 Step 1 Count the total number of valence electrons in the structure Step 2 Arrange the peripheral atoms around the central atom/structure and single bond them Step 3 Place remaining electrons around peripheral atoms. Place any extra electrons around the central atom. Step 4 Calculate the formal charges and minimize it by preparing resonance structures Formal Charge = Valence electrons lone pair electrons bonds Incomplete Valence: Expanded Valence: Pavel Sedach

18 Systematic Lewis Structures 18 Step 1 Count the total number of valence electrons in the structure Step 2 Arrange the peripheral atoms around the central atom/structure and single bond them Step 3 Place remaining electrons around peripheral atoms. Place any extra electrons around the central atom. Step 4 Calculate the formal charges and minimize it by preparing resonance structures Formal Charge = Valence electrons lone pair electrons bonds Expanded Valence: Pavel Sedach

19 Understanding Line Diagrams 19 C has 4 bonds, N has 3 bonds, O has 2 bonds. To save time drawing structures, we form line diagrams Because C behaves so reproducibly and forms 4 bonds, we can use line diagrams to represent organic structures. Every vertex (intersection of 2 or more lines) is a carbon atom and it is assumed that C forms 4 bonds Pavel Sedach

20 Priority Group Carboxylic Acids Esters Amides Aldehydes Ketones Functional Groups 20 What functional groups are in the following compound? Are there lone pairs missing? Draw a condensed diagram (e.g. where there is a carbon and hydrogen, write CH) 6 Alcohols Amines 7 8 Ethers Alkenes 9 10 Alkynes 11 Alkyl Halides 12 Alkanes

21 Drawing Proper Tetrahedral Shapes 21 All of these drawings represent EXACTLY the same molecule viewed from different angles There are VERY few ways to draw a proper tetrahedral structure. Fundamental structures are circled above in the same color. What is wrong with the structures below? For organic structures, we typically put a straight chain and just have wedge/hash poking out to one side: Pavel Sedach

22 Drawing Proper Trigonal Planar Shapes: 22 Name the functional group, name the structure and draw 3 different VSEPR diagrams:

23 Resonance, Bond Order and Average Charge 23 Identify the major, minor and intermediate resonance contributors: Does the above compound have an effective resonance hybrid?

24 Resonance, Bond Order and Average Charge 24 Identify the major, minor and intermediate resonance contributors: Does the above compound have an effective resonance hybrid?

25 Resonance, Bond Order and Average Charge 25

26 Resonance, Bond Order and Average Charge 26

27 27 Organic Compounds and Valence Bond Theory

28 Organic Structures Adding Missing Bonds and Electron Pairs 28

29 Single, Double and Triple Bonds 29 Bond Strength and Bond Dissociation Energy (Bond Energy) Bond Length Single Bond Double Bond Triple Bond < < > > Single Bond Double Bond Triple Bond Arrange the following bonds according to their bond order (high to low) i iii, N-O bond ii C-N bond Arrange them again, this time from long to short length Pavel Sedach

30 Orbital Hybridization (Valence Bond Theory) 30 Count the number of things attached, count the number of orbitals used! p s d p p p s s s +

31 Energy diagrams for hybridized atoms 31 Energy diagram of Unhybridized C 2p How many pi bonds are there in the following molecule? 2s Unhybridized N 2p 2s Unhybridized O 2p 2s bonds are made from sp orbitals bonds are made from p orbitals they are any bond above a sigma bond =, =, =, =,

32 and Bonding Frameworks aka. Valence Bond Theory 32 Valence bond theory is an extension of VSEPR. The two are distinct from MO theory. Bonding Framework Bonding Framework x-axis X X X X

33 and Bonding Frameworks aka. Valence Bond Theory 33 Bonding Framework Bonding Framework X X

34 and Bonding Frameworks aka. Valence Bond Theory 34 Bonding Framework Bonding Framework y y

35 VSEPR Structure Hybridization Electronic Shape Molecular Shape Bond Angles Notes linear linear 180 Pavel Sedach 35 trigonal planar trigonal planar 120 trigonal planar bent, < 120 < 120 Always has a net dipole tetrahedral or Td tetrahedral or Td tetrahedral or Td trigonal pyramidal < Always has a net dipole tetrahedral or Td bent, < < Always has a net dipole trigonal bipyramidal trigonal bipyramidal trigonal bipyramidal trigonal bipyramidal octahedral or Oh octahedral or Oh or square bipyramidal trigonal bipyramidal 120, 90 *180 is also a possible angle if looking axial to axial see-saw 120, 90, 180 Always has a net dipole. 180 is axial to axial. Equator has more room so lone pairs go there (120 > 90 so more room at equator) t-shaped 90, 180 Always has a net dipole. 180 is axial to axial linear is axial to axial octahedral or Oh square pyramidal 90, < 90 Always has a net dipole octahedral or Oh square planar 90 unlikely octahedral or Oh t-shaped < 90 Always has a net dipole. Never experimentally observed. unlikely octahedral or Oh bent, < 90 < 90 Always has a net dipole. Never experimentally observed. 90

36 Does the molecule have resonance? 36 Resonance is movement of electrons through bonds

37 Show possible Resonance Structures for the following compounds 37

38 38 Isomers Good place to take a break for Day 1

39 Not Isomers ISOMERS Constitutional 39 NO Do the compounds have the same molecular formula? YES Isomers Same formula ( ), different skeleton! Are the atoms connected the same way? YES NO Conformational Stereoisomers Constitutional Can the compounds be interconverted by rotation about single bonds? YES NO Geometric Rotate around single bond Conformational Configurational Z-but-2-en-1-ol E-but-2-en-1-ol Is the isomerism at a double bond? YES NO Optical Geometric Optical Look for a carbon atom with 4 different groups Pavel Sedach

40 Isomers Isomers YES Do the compounds have the same molecular formula? NO Constitutional NO Are the atoms connected the same way? YES Stereoisomers Conformational YES Can the compounds be interconverted by rotation about single bonds? NO Configurational Is the isomerism at a double bond? Not Isomers e.g. vs. NO Optical YES Geometric Look for a carbon atom with 4 different groups attached cis-but-2-en-1-ol trans-but-2-en-1-ol

41 Constitutional Isomers of 41 Draw a molecule that is a ketone, name it: Draw a molecule that is an aldehyde, name it: Draw a molecule that is an ether: Draw a molecule that is an alcohol, name it:

42 Newman Projections and Conformational Isomers (conformers) of Ethane 42 Energy Eclipsed Eclipsed Staggered Staggered Pavel Sedach

43 Isomers Isomers YES Do the compounds have the same molecular formula? NO Constitutional NO Are the atoms connected the same way? YES Stereoisomers Conformational YES Can the compounds be interconverted by rotation about single bonds? NO Configurational Is the isomerism at a double bond? Not Isomers e.g. vs. NO Optical YES Geometric Look for a carbon atom with 4 different groups attached cis-but-2-en-1-ol trans-but-2-en-1-ol

44 Configurational Isomers - Optical Isomers 44 4 different groups bonded to one atom (usually Carbon) Is the following molecule chiral? (optically active)? If so, draw its optical isomer.

45 Configurational Isomers Geometric Isomers 45 cis/trans longest carbon chain E/Z largest atom (Cahn Ingold Prelog Rules)

46 Which molecule is the most stable? Why? 46 Does the following compound have a geometric isomer? Does the following compound have a conformational isomer? A geometric isomer?

47 47 Intermolecular Forces Good place to take a break for Day 1

48 Functional Groups 48 Name the functional group. Draw any missing lone pairs. Name the compound. Give the shape around each atom AND state whether it is drawn correctly according to VSEPR: correct? correct? correct? correct?

49 Functional Groups 49 Name the functional group. Draw any missing lone pairs. Name the compound. Give the shape around each atom AND state whether it is drawn correctly according to VSEPR: correct? correct? correct? correct?

50 Functional Groups 50 Name the functional group. Draw any missing lone pairs. Name the compound. Give the shape around each atom AND state whether it is drawn correctly according to VSEPR: correct? correct? correct?

51 Basic Intermolecular Forces 51 London Dispersion Forces (Van Der Waals Forces) Dipole-Dipole Bonding Compound State at 25 C - GAS - LIQUID - SOLID

52 Basic Intermolecular Forces 52 Hydrogen Bonding occurs in the FON elements (HF, OH, NH) The relative strength of London Dispersion (temporary dipole) forces to Dipole Forces to Hydrogen Bonding is LDF : DD : HB of 1:10:1000

53 Effects of Intermolecular Forces on Boiling Point 53 Arrange the following from high to low boiling point

54 Review 54 Methyl ethyl ether is a gas at room temperature (boiling point = 8 C), but 1-propanol is a liquid (boiling point = 97 C). This difference can be explained mostly by: a) Covalent bonding b) London Dispersion forces c) Dipole-dipole interactions d) Hydrogen bonding

55 Review 55 Which of the following has the highest boiling point at 1 atm?

56 Review 56 Rank the following compounds on the basis of decreasing boiling point:

57 The ability to stack and London dispersion forces: 57 There is a relationship between some of the compounds below. What is the relationship and which compounds share it? Arrange all of the above compounds in order of boiling point (high to low)

58 Expanded Intermolecular Forces for Mixed Solutions 58 Interaction Polarizability (London dispersion forces) Induced dipole-induced dipole Factors of Interaction Dipole-induced dipole Dipoledipole Ion-induced dipole Dipole moment of polar molecule and polarizability of nonpolar molecule. Dipole moment Ion and a compound that has LDF only Ion charge, magnitude of dipole Ion-dipole Hydrogen bonding Molecule contains H-F or O-H or N-H Can hydrogen bond to secondary molecule that has F, O or N with a free lone pair and no Hs

59 Intermolecular Forces 59 name

60 Intermolecular Forces 60 name

61 Intermolecular Forces 61

62 Can apply to materials e.g. hydrophilic vs. hydrophobic 62 hydrophilic

63 Reactions 63 Show the reaction of lithium hydroxide with ethanoic acid Show the reaction of ammonia with boron trifluoride

64 Reactions 64 Show the reaction of triethylamine with butanoic acid Show the reaction of sodium oxide with water

65 65 Cumulative Review

66 Electronic Configurations and Quantum Numbers 66 n= n=5 n=4 n=3 n=2 Zinc Cadmium n=1 e- p + n Arsenic Copper *What are all the exceptions to electron filling?

67 Put a square around core electrons and circle the valence electrons 67 Vanadium (V): s orbitals OR [Ar] p orbitals Ge: Ti: d orbitals As Zn: Ag: The Valence Electrons are the highest n-value and highest energy orbitals, including the d-orbitals ONLY if they are unfilled!

68 Electronic Configurations 68 Which element is depicted in the diagram below? n = n = 5 n = 4 5s 4s 3d Energy n = 3 n = 2 3s 2s 2p 3p Aufbau Principle (Low to High Energy) Hunds Rule (Single before Pairing) Pauli Exclusion Principle Diamagnetic? Paramagnetic? n = 1 1s

69 Draw the Electronic Configuration for Co 69 Is cobalt paramagnetic or diamagnetic? n = 5 n = 4 5s 4s 3p 3d Energy n = 3 3s 2p n = 2 2s n = 1 1s

70 Quantum Numbers 70 Symbol Possible values Principal Quantum Number (Shell/Energy Level) Angular Momentum QN ( ) (Subshell or Orbital Shape) SIZE SHAPE Magnetic QN ( ) (Specific Orbital in Subshell) ORIENTATION Electron spin ( ) (Orientation of e- whether up or down) learnfaster.ca

71 Electronic Configurations 71 What are the quantum numbers of the circled electrons? n = n = 5 n = 4 5s 4s 3p 3d Energy n = 3 n = 2 3s 2s 2p What atom can this possibly be? n = 1 1s

72 Periodic Properties 72 Atomic Radius Atomic Radius Pavel Sedach

73 Effective Nuclear Charge 73 Effective nuclear charge = # protons - # core electrons. Its essentially an estimate of the number of protons pulling that electron in towards the atom. If an electron feels a higher effective nuclear charge, it is HARDER to remove. B C N O Protons Core Electrons Increases left to right across the periodic table. Due to the way is calculated in Chem 201, we dont see a decrease going down a Group but we should. for the d-block is generally not discussed but even unfilled d acts as core. Pavel Sedach

74 Ionization Energy is the energy needed to remove an e- from an atom (endothermic) 74 Equation for Ionization: Ionization energy (kj/mol) is ALWAYS endothermic (it always takes energy to remove electrons from an atom!) 1st Ionization Energy (kj/mol) Period 2 Period Column/Group (not including the d-block) Explain why the ionization energy of Mg is greater than Al? F is greater than O? Ne is greater than F? Why does period 3 have a greater ionization energy than period 4? Pavel Sedach

75 Successive Ionization Energies of Carbon 75 Ionization energy Enthalpy 1 st 1087 Beginning Shorthand Configuration [He] Equation [He] Final Shorthand Configuration 2 nd 2353 [He] [He] 3 rd 4621 [He] [He] 4 th th The second ionization energy for an atom is always greater than the first. Why? Where is there an enormous jump in ionization energy and why? Pavel Sedach

76 Electron Affinity - Magnitude of how exothermic the absorption of an electron is. 76 Why does Nitrogen have a lower electron affinity than Oxygen? Electron Affinity (kj/mol) What process is described by the enthalpy of attachment of the second electron of Aluminum? Pavel Sedach

77 Review N, st Ionization Energy (kj/mol) Group 15 O, Group P, As, +947 S, Se, Period/Row (n=2,3,4) What is the of the Group 1 elements and the Group 2 elements? Why is the ionization energy of the Group 15 elements higher than that of the Group 16 elements? Why is the ionization energy of N bigger than Sulfur? Pavel Sedach

78 Atomic Radius is the distance from the nucleus to the outermost electrons. 78 Atomic radius decreases from left to right and across the periodic table. Atomic Radius increases from top to bottom of the periodic table. Small Radii Increasing Size Large Radii Ionic Radius Cation Loses Electron Neutral Increasing Size Gains Electron Anion Cations are ALWAYS smaller than their neutral atoms Anions are ALWAYS larger than their neutral atoms Pavel Sedach

79 Review What are the four periodic trends and how do they vary on the periodic table? 2. What are the exceptions to some trends and why do they occur? 3. Rank the following in order of ionic radius: Pavel Sedach

80 Orbital Diagrams of the 2s 80 BOUNDARY DIAGRAMs (also known as LOBE DIAGRAMs) RADIAL PROBABILITY DIAGRAM RADIAL PROBABILITY DIAGRAM (typical view) -r +r r ELECTRON DENSITY DIAGRAM (also known as SCATTER or DOT DIAGRAMs) spherical or radial node Pavel Sedach learnfaster.ca

81 The following shows the shapes of the radial distribution functions of the atomic orbitals 81 subshell 1s 2s 3s 2p 3p 3d spherical nodes Radial Probability Diagram Scatter Dot Diagram

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