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Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
Chapter 26   skeleton notes
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  • 1. Organic Chemistry Selected sections Ch 26 + Ch 11 The chemistry of life and living things The chemistry of carbon compounds Chem 1AA3 2 Chem 1AA3 3 Evolution of the field 1
  • 2. Why is organic chemistry important? • To understand how we interact with – other organisms (food & nutrients, infections), – our environment (aromas, pollutants), – drugs, and – ourselves (metabolism, growth, immunity, cancer) • To understand how things are made, what they're made of, and how they react with each other Chem 1AA3 4 Why is organic chemistry important? • Because it is central to: Chemistry Chemical Biology Biochemistry Biology Engineering Material sciences Forensic Sciences Medicine • To get into graduate/medical/dental school! Chem 1AA3 5 Medical Application: Molecular Imaging 18F-fluorodeoxyglucose Chem 1AA3 6 2
  • 3. Organic Chemistry Components 1) Structure: The connectivity and 3-D nature of compounds 2) Theory: Structure and reactivity in terms of atoms and the electrons that bind them together Chem 1AA3 7 Components (continued) 3) Synthesis: How to design new molecules – and then make them Chem 1AA3 8 Organic Compounds • Why is one element in the periodic table given its own field? – 98% of all known chemical substances are organic • Inorganic chemistry = the chemistry of everything else • Nearly all pharmaceuticals are organic in nature Chem 1AA3 9 3
  • 4. Organic Compounds: Biological 11-cis-retinal H O NH2 Serotonin (neurotransmitter) HO N H Chem 1AA3 10 Diagnostic iClicker Question Which is the cis double bond in 11-cis-retinal? (b) (d) (c) (a) (e) H O Chem 1AA3 11 Organic Compounds: Medicines N EtO O Me2N N N N S NH N O O O Tamoxifen H N O OH N Lipitor Viagra OH O OH F Chem 1AA3 12 4
  • 5. Organic Compounds: Drugs CH3 OH CH3 CH3 HN N H Stanozolol Chem 1AA3 13 Organic Compounds: Industrial Chemicals HN Indigo dye (blue jeans) O O NH CO2H H N H 2N O Aspartame OMe O Chem 1AA3 14 Organic Compounds: Natural Products O O N Cocaine O O N HO Quinine MeO N Chem 1AA3 15 5
  • 6. Alkanes Section 26-1, 26-2 Alkanes • Hydrocarbons – the simplest organic compounds (CnH2n+2) • Saturated (use all bonding e− to make single bonds) • Methane (various representations): Chem 1AA3 17 Chem 1AA3 18 Ethane (C2H6) 6
  • 7. Propane (C3H8) Chem 1AA3 19 Drawing Organic Molecules • Guideline 1: Draw molecules in a Zig-Zag shape versus linear structures vs CH3CH2CH2CH2CH2CH3 • Guideline 2: You can assume there are Hatoms attached to carbon atoms in a ZigZag structure giving a valence of 4 OH H H H H H H OH H Chem 1AA3 20 Drawing molecules (continued) • Guideline 3: For reactions, draw out the functional groups in detail and include lone pairs (electrons) OH O Chem 1AA3 21 7
  • 8. Advice and hints • Be neat – messy structures lead to mistakes • Count your carbon atoms! • Count the substituents on carbon atoms (including implied H atoms) • In this course, there are never more than four bonds to carbon 22 Chem 1AA3 PH Diagnostic iClicker Question Which of the following wedge-and-dash drawings of propane is incorrect? (a) HH H H H H H H H H H (d) H H H H H H H H H H H H H H H H H H H (c) (b) (e) don't know H H 23 Chem 1AA3 PB Diagnostic iClicker Question Which of the following wedge-and-dash drawings of propane is incorrect? H H H H H H (a) H (c) H HH H H H H (b) H H H H H H (d) H H H H H H H H H H (e) don't know H H Chem 1AA3 24 8
  • 9. JV Diagnostic iClicker Question Which of the following wedge-and-dash drawings of propane is incorrect? (a) (c) H H H H H H H H H (d) HH H H H H H H H H H H H H H H H H H H (b) H (e) don't know H H Chem 1AA3 25 HS Diagnostic iClicker Question Which of the following wedge-and-dash drawings of propane is incorrect? H (a) H H H H H H H H (b) H H (c) H H H H H (d) H H H H H H H H H H H H H H H (e) don't know H Chem 1AA3 26 Chem 1AA3 27 Fuels: Octane Number Octane Number: used to indicate the resistance of a motor fuel to “knock” p. 1084 9
  • 10. Fuels: Alcohols Alcohols can also be used as fuels: CH3OH(l) + 1.5O2(g) CH3CH2OH(l) + 3O2(g) CO2(g) + 2H2O(l) ∆Ho = -726 kJ mol-1 2CO2(g) + 3H2O(l) ∆Ho = -1367 kJ mol-1 ∆H°(combustion) for CH4, methane -891 kJ/mol C2H6, ethane -1560 kJ/mol http://pubs.acs.org/cen/coverstory/85/8551cover.html Chem 1AA3 28 Structural Diversity Isomers, cycloalkanes Concept Check: Skeletal/Structural Isomerism Skeletal or structural isomers have: - The same molecular formula but different connectivity. - Different physical properties. Concept check: Draw structural isomers of C5H12 Chem 1AA3 30 10
  • 11. Concept Check: Solution H H H H H H C C C C C H H H H H H pentane H H C H H H H H C C C C H H H H H H H C H H H H C C C H H H H C H H 2-methylbutane 2,2-dimethylpropane Chem 1AA3 31 Conformations of alkanes Newman Projections Lower E Chem 1AA3 32 Conformation versus configuration • Conformation: arrangement of atoms in a molecule that can be changed by simple rotation of single bonds, without breaking any bonds. • Configuration: the permanent geometry of a molecule resulting from the spatial arrangement of its bonds. – Must break bonds to change configuration. versus Chem 1AA3 33 11
  • 12. Conformations of ‘disubstituted ethane’ H H R' R H H Staggered R R H H H H H H R R' R' H H H R' H H H Lowest E 34 Chem 1AA3 Eclipsed Conformations Eclipsed HR H H H R' HR R' R H H H H H R' H H Highest E • All eclipsed conformations have higher energy than all staggered conformations. 35 Chem 1AA3 PH Formative iClicker Question #1 Which conformation has the lowest (most favourable) energy? R (a) H H R R' RH H H (b) R' H H (c) R (d) H R' H H H H H H R' R (e) H H H H H R' H Chem 1AA3 36 12
  • 13. PB Formative iClicker Question #1 Which conformation has the highest (least favourable) energy? R R R' RH H H (a) H H (b) (c) H H R' R (d) H H R R' H H H H R' R' (e) H H H H H H H 37 Chem 1AA3 JV Formative iClicker Question #1 Which conformation has the highest (least favourable) energy? R R' H (a) RH R H H H H (b) H H H (c) H H H R' R' R R' (d) H H R H R' (e) H H H H H 38 Chem 1AA3 HS Formative iClicker Question #1 Which conformation has the lowest (most favourable) energy? R (a) RH R H R' H H H H H (b) H H (c) H H H R' R' R R' (d) H H R H R' (e) H H H H H Chem 1AA3 39 13
  • 14. Ring Structures: Cycloalkanes CnH2n Chem 1AA3 40 Molecules are not always flat: Cyclohexane Boat Chair Chem 1AA3 41 Chem 1AA3 42 Boat conformation movie 14
  • 15. Boat conformation movie Chem 1AA3 43 Chem 1AA3 44 Chem 1AA3 45 Chair conformation movie Chair conformation movie 15
  • 16. Axial vs. equatorial substituents. Cyclohexane Conformations Boat Chair Equatorial H atoms are pink, axial H atoms are blue Chem 1AA3 46 Ring Strain in Cycloalkanes propane • Bond angles (at C atoms) 109.5o cyclopropane • Bond angles (at C atoms) 60o • H-atoms are eclipsed Chem 1AA3 47 Naming Section 26-1 16
  • 17. Naming • Chemistry is a visual science: Structures are key to understanding reactivity and physical properties • Systematic nomenclature: IUPAC rules (assumed knowledge) IUPAC: International Union of Pure and Applied Chemistry See the supplementary information about naming in ELM for more information Chem 1AA3 49 Names of common compounds O O Acetone Acetaldehyde Acetic acid O O H O Formic acid H OH OH Ethyl acetate Ether OCH2CH3 CH3CH2OCH2CH3 O Acetyl group H3C Chem 1AA3 50 Common compounds (continued) Benzene Toluene OH Phenol Pyridine N Chem 1AA3 51 17
  • 18. Some Common Alkyl Substituents (Table 26.1) Chem 1AA3 52 Chem 1AA3 53 Chem 1AA3 54 More alkyl names n-butyl R sec-butyl R isobutyl R R tert-butyl Substituents Vinyl groups Allyl groups R R R Phenyl groups Example: Allyl acetate O O 18
  • 19. PH Diagnostic iClicker Question What is the name of this compound? O O (a) sec-butyl acetate (b) butyl methyl carboxylic acid (c) ethyl butanoate (d) isobutyl acetate (e) n-butyl acetate Chem 1AA3 55 PB Diagnostic iClicker Question What is the name of this compound? O O (a) sec-butyl acetate (b) propyl butanoate (c) ethyl butanoate (d) isobutyl acetate (e) n-butyl propanoate Chem 1AA3 56 JV Diagnostic iClicker Question What is the name of this compound? O O (a) sec-butyl acetate (b) butyl methyl carboxylic acid (c) ethyl butanoate (d) isobutyl acetate (e) n-butyl acetate Chem 1AA3 57 19
  • 20. HS Diagnostic iClicker Question What is the name of this compound? O O (a) sec-butyl acetate (b) butyl methyl carboxylic acid (c) ethyl butanoate (d) isobutyl acetate (e) n-butyl acetate Chem 1AA3 58 Reactions of Alkanes Section 26-2 Concept Check C8H18(l) + O 2(g) ? 1) What are the products of the reaction at 298K? 2) Write a balanced chemical equation 3) Predict the signs of ∆H, ∆S and ∆G 4) What type of reaction is shown? Chem 1AA3 60 20
  • 21. Concept Check: Solution C8H18(l) + 25 2 O2(g) → 8 CO2(g) + 9 H2O(l) ∆H° = -5.48 × 103 kJ mol−1 (exothermic!) ∆So is negative ∆Go = ∆H°-T∆So, ∆Go should be negative (∆H° is large) Reaction type: Combustion, redox Chem 1AA3 61 Chem 1AA3 62 Halogenation CH4 X2 CH3X + HX + CH3-CH3 Light or heat Halogenation Initiation: Propagation: Cl-Cl ∆ or hν → 2 Cl· H3C-H + Cl· → H3C· + HCl H3C· + Cl2 → H3C-Cl + Cl· Termination: Cl· + Cl· → Cl-Cl H3C· + Cl· → H3C-Cl H3C· + H3C· → H3C-CH3 Applicable also for F2 (often explosive), Br2, I2 (slow) Chem 1AA3 63 21
  • 22. Grignard Reagent Mg R X Et2O R MgX X = Cl, Br or I Mg Cl Et2O MgCl Look at the change in oxidation state of the Mg: Mg(0) Question: What gets reduced? Cl Mg(II) Mg2+ClChem 1AA3 64 Bonding in alkanes Hybridization Section 11-3 Review: Electronic Structure and Bonding The following section, up to "Review: p-orbitals", is assumed knowledge and will not be discussed in class. The Atom: A dense nucleus surrounded by a much larger extranuclear space Chem 1AA3 66 22
  • 23. Review: Principal Energy Levels • Electrons are confined to shells defined by the principal quantum number (n) • n = 1, 2, 3 … • Each shell can contain 2n2 electrons • The lower the value of n-the lower the energy of the shell (nearest to the nucleus) Chem 1AA3 67 Review: Orbitals • Shells are divided into sub-shells labelled s, p, d, f • p, d, and f orbitals are further divided up based on their spatial orientation Chem 1AA3 68 Review: Orbitals in Shells Shell n=1 n=2 Orbitals in that shell 1s 2s, 2px, 2py, 2pz n=3 3s, 3px, 3py, 3pz, + 5 3d Chem 1AA3 69 23
  • 24. Review: Electron Configuration Three principles/rules are used to determine the electron configuration: Aufbau Principle Pauli Exclusion Principle Hund’s rule Chem 1AA3 70 Review: Orbitals (subshells) • Each type of orbital (s, p, d, f) has a distinct shape • The shape represents the probability of finding an electron (quantum mechanics) • Organic chemists are interested in shells 1, 2, and sometimes 3 Chem 1AA3 71 Chem 1AA3 72 Review: s-orbitals Spherical: 24
  • 25. Review: p-orbitals 3 of them: px, py, pz Chem 1AA3 73 Example: Carbon 1s22s22p2 The outer most electrons of atoms (valence electrons) govern the chemical and physical properties Chem 1AA3 74 p-Orbital Shapes • The p-orbitals in carbon are at 90o to each other • Atoms bonding to a carbon atom should therefore be situated at 90o to each other Chem 1AA3 75 25
  • 26. Methane - CH4 • Problem: the shape of methane is tetrahedral (AX4) • Bond angles are 109.5o not 90o Chem 1AA3 76 Hybridization • Comes from the word hybrid which means something of mixed origin or composition • Hybrid orbitals arise by combination of atomic orbitals within an atom Chem 1AA3 77 sp3 Hybridization (section 11-3) 1s22s22p2 4 sp3 hybrid orbitals Ground state 4 atomic orbitals Chem 1AA3 78 26
  • 27. sp3 Hybridization Chem 1AA3 79 sp3 Hybridization The number of hybrid orbitals is equal to the number of combining atomic orbitals Combine one 2s orbital and three 2p orbitals four sp3 orbitals Chem 1AA3 80 Bonding-methane Overlap of sp3 orbitals from carbon and 1sorbitals from hydrogen 109.5o End-on (or end-to-end) overlap produces sigma (σ) bonds. End-on overlap of sp3-orbitals also produces σ-bonds. Chem 1AA3 81 27
  • 28. PH Diagnostic iClicker Question How many σ-bonds are there in this molecule? H H H H H H (a) 1 (b) 2 (c) 7 (d) 14 Chem 1AA3 82 PB Diagnostic iClicker Question How many sp3-orbitals are there in this molecule? H H H H H H (a) 1 (b) 2 (c) 7 (d) 8 Chem 1AA3 83 JV Diagnostic iClicker Question How many sp3-sp3 σ-bonds are there in this molecule? (a) 1 (b) 2 (c) 7 (d) 14 Chem 1AA3 84 28
  • 29. HS Diagnostic iClicker Question How many sp3-hybridized atoms are there in this molecule? (a) 2 (b) 6 (c) 8 (d) 26 Chem 1AA3 85 Chem 1AA3 87 Moving beyond alkanes: Functional Groups Sample Problem CO2H H N H2N O OMe O What functional groups do you see? 29
  • 30. Sample Problem: Solution Ester Carboxylic Acid CO2H H N H2N O OMe O Amine Aromatic/Arene Amide Chem 1AA3 88 Chem 1AA3 89 Chem 1AA3 90 Table 26.2 * p. 1080 * Not a functional group Table 26.2 carboxylic acid anhydride O R O O O R H3 C O O CH3 30
  • 31. Table 26.2 You must be able to recognize these functional groups 91 Chem 1AA3 PH Diagnostic iClicker Question Which functional group is not found in this molecule? NH2 HO N (a) aryl (b) amine (c) amide (d) phenol H 92 Chem 1AA3 PB Diagnostic iClicker Question Which functional group is not found in this molecule? H N O (a) aryl (b) hydroxyl (c) aryl halide (d) ester OH OH O N OH F Chem 1AA3 93 31
  • 32. JV Diagnostic iClicker Question Which functional group is not found in this molecule? O (a) amide (b) ketone (c) aryl halide (d) alkene H N N H Cl O Chem 1AA3 94 PB Diagnostic iClicker Question Which functional group is not found in this molecule? N EtO N N N (a) aryl (b) hydroxyl (c) amine (d) amide S NH N O O O Chem 1AA3 95 Synthesis 1) Functional group interconversion – ex. Converting an aldehyde to an alcohol O OH H 2) Carbon-carbon bond forming reactions – ex. Grignard reaction R MgX 1. CO2 2. H3O+ R CO2H Chem 1AA3 96 32
  • 33. Alkenes Section 26-3 Alkenes (CnH2n) Chem 1AA3 98 Multiple Covalent Bonds • Ethylene has a double bond in its Lewis structure • VSEPR says trigonal planar shape at C sp2 hybridization p. 435 Chem 1AA3 99 33
  • 34. sp2 Hybrid Orbitals (section 11-4) Combine one 2s orbital + two 2p orbitals three sp2 orbitals (+ one 2p orbital left over) Hybrid orbital lobes pointing in the direction of an equilateral triangle: bond angles 120o Chem 1AA3 100 Chem 1AA3 101 sp2 Hybrid Orbitals sp2 Hybrid Orbitals • The extra p-orbital can be used to form πbonds • π-bonds are covalent bonds that form by the sideways overlap of parallel p-orbitals eclipsed p-orbitals π-bond staggered p-orbitals no π-bond Chem 1AA3 102 34
  • 35. Ethene Section 11-4 Overlap above and below plane of atoms gives 1 π bond Chem 1AA3 103 Chem 1AA3 104 Chem 1AA3 105 Recall: Conformations of alkanes Alkenes have restricted rotation Geometric Isomers cis p. 1086 trans 35
  • 36. Fats and Oils: Triacylglycerols Fat: solid at room temp. Oil: liquid at room temp. O OH O R O OH O R OH O glycerol R O Key Factors: • Chain length (MW) • Number of double bonds • Geometry of the double bonds triacylglycerol Chem 1AA3 106 Chem 1AA3 (More information available on p. 1137-1139) 107 Concept Check Which of these two fatty acids has the higher melting point and why? O RO Linoleic acid (R = H) O RO Stearic acid (R = H) Concept Check: Solution O RO Linoleic acid (R = H) mp = -5oC Less efficient packing because of kink in chain geometry, therefore weaker intermolecular forces and lower melting point. O RO Stearic acid (R = H) mp = 70oC Straight chain allows more efficient packing, therefore stronger intermolecular forces and higher melting point. Chem 1AA3 108 36
  • 37. Impact of Geometry Chem 1AA3 109 Chem 1AA3 110 Chem 1AA3 111 The E,Z System of Nomenclature • Need a new system • Higher priority higher atomic number Z isomer E isomer p. 1106 Concept Check Label the tamoxifen isomers as E or Z: Me2N Me2N O O Z E 37
  • 38. PH Formative iClicker Question #2 Which molecule has an E configuration? (a) Cl (b) F (c) Cl (d) (e) F Chem 1AA3 112 PB Formative iClicker Question #2 Which molecule has an E configuration? (a) (b) (c) F (d) F (e) F F Chem 1AA3 113 JV Formative iClicker Question #2 Which molecule has an E configuration? (a) (b) (c) Cl (d) Cl (e) Cl Cl Chem 1AA3 114 38
  • 39. HS Formative iClicker Question #2 Which molecule has an E configuration? (a) (b) F Cl F (c) F Cl (d) (e) Cl Chem 1AA3 115 Degree of Unsaturation • A hydrocarbon with one π-bond or ring has two fewer H-atoms than a linear alkane; it is said to have “1 degree of unsaturation” • The molecular formula of a hydrocarbon can be used to determine the number of π-bonds and/or rings in a compound. • The "degree of unsaturation" (d.o.u.) can be calculated using: d.o.u. = (2n + 2 - m) / 2 (m = # of H-atoms, n = # of C-atoms) Chem 1AA3 116 Degree of Unsaturation (d.o.u.) • Rings count as one d.o.u. • Double bonds count as one d.o.u. • Triple bonds count as two degrees of unsaturation • d.o.u. does not give the type or number of each type of unsaturation (ring, π bond); this is determined using spectroscopic techniques (2nd year) • Note: a molecule can be saturated yet have a degree of unsaturation (e.g., cyclohexane) Chem 1AA3 117 39
  • 40. PH Diagnostic iClicker Question Which molecule has the highest degree of unsaturation? (a) (b) (c) Chem 1AA3 118 PB Diagnostic iClicker Question Which molecule has the highest degree of unsaturation? (a) (b) (c) Chem 1AA3 119 JV Diagnostic iClicker Question Which molecule has the lowest degree of unsaturation? (a) (b) (c) Chem 1AA3 120 40
  • 41. HS Diagnostic iClicker Question Which molecule has the lowest degree of unsaturation? (a) (b) (c) Chem 1AA3 121 Reactions involving alkenes Section 26-3 Addition Reactions Not observed Markovnikov’s rule: the H atom ends up attached to the carbon atom of the double bond that has the most hydrogen atoms to start with. p. 1087-1088 Chem 1AA3 123 41
  • 42. Explanation of Markovnikov’s rule + X Br - H H Br δ+ 2o carbocation - less stable δ- H + Br - 3o carbocation - more stable H Br haloalkane product Chem 1AA3 124 Curly arrows • The curly arrow represents electrons moving from the alkene π-bond to the proton of HBr, forming a C-H bond. H Br δ+ δ- • We will examine this in more detail in nucleophilic substitution reactions (Section 26-11) Chem 1AA3 125 Carbocation stability Stability: H3C+ < methyl < < 1° < < 2° < 3° Why do alkyl substituents increase cation stability? Steric: Br H3C H3C CH3 Br H3C H3C CH3 The cationic carbon rehybridizes from sp3 to sp2, relieving the steric clash between substituents Chem 126 1AA3 42
  • 43. Carbocation stability Why do alkyl substituents increase cation stability? Electronic: CH3 H3C CH3 Alkyl substituents are electron donating compared with H. Donating electrons to an electron deficient (positively charged) centre stabilizes it. δ+ δ- = a permanent electric dipole Chem 1AA3 127 PH Formative iClicker Question #3 What is the expected product, according to Markovnikov's rule? HBr Br (a) (b) Br Br Br Br (c) (d) Chem 1AA3 128 PB Formative iClicker Question #3 What is the expected product, according to Markovnikov's rule? HI (a) (b) I I I I (c) I (d) Chem 1AA3 129 43
  • 44. JV Formative iClicker Question #3 What is the expected product, according to Markovnikov's rule? HBr (b) (a) Br Br (c) (d) Br Br Chem 1AA3 130 HS Formative iClicker Question #3 What is the expected product, according to Markovnikov's rule? HCl Cl (b) (a) Cl Cl Cl (c) (d) Cl Chem 1AA3 131 Hydration Reaction • Addition is favoured (forward reaction) in dilute acid • Elimination is favoured (reverse reaction) in concentrated acid Chem 1AA3 132 44
  • 45. Hydration also follows Markovnikov's rule H H 2O HO H H3O+ H + O H JV? H + HO H3O+ H H2O O H H Chem 1AA3 133 Chem 1AA3 134 Reduction of Alkenes Hydrogenation H H H H catalyst Application: Hydrogenation of Natural Products O O CH2OC(CH2)7CH CH2OC(CH2)16CH3 CH(CH2)7CH3 O O CHOC(CH2)7CH O CH(CH2)7CH3 3H2 Ni catalyst heat CH2OC(CH2)16CH3 CH2OC(CH2)7CH CH(CH2)7CH3 Unsaturated vegetable oil (olein-liquid) CHOC(CH2)16CH3 O Solid cooking fat-shortening (stearin, solid) (More information available on p. 1137-1139) Chem 1AA3 135 45
  • 46. Partial Hydrogenation O RO H2 (1 equiv.) catalyst O RO mixture H saturated at either double bond, e.g. H Chem 1AA3 136 cis versus trans fatty acids cis-9-octadecenoic acid (Oleic acid) trans-9-octadecenoic acid (Elaidic acid) Chem 1AA3 137 Alkynes Section 26-3 46
  • 47. Alkynes According to VSEPR, alkynes are linear Chem 1AA3 p. 1085 139 sp Hybrid Orbitals • Combine one 2s orbital + one 2p orbital two sp orbitals (+ two 2p orbitals left over) sp hybridization Section 11-4, p. 436 Chem 1AA3 140 Chem 1AA3 141 sp Hybrid Orbitals 47
  • 48. Acetylene: Orbitals • Acetylene, C2H2, has a triple bond. • Linear at carbon Chem 1AA3 142 Reactions of Alkynes Reduction of Alkenes and Alkynes H H H H catalyst CH3CH2C CCH3 CH3CH2C CCH3 + H2 + H2 Pd/C CH3CH2CH2CH2CH3 Et Lindlar's catalyst H CH3 H Cis isomer only! p. 1088 Chem 1AA3 144 48
  • 49. The Carbonyl Group: ketones and aldehydes Section 26-6 Examples CH3OH Ketones H3C O O O Acetone Methyl ethyl ketone (MEK) Aldehydes Testosterone O O O H H H H Benzaldehyde Formaldehyde Cinnamaldehyde Chem 1AA3 p. 1094-1095 146 Structure and Polarity 121o H O 121o 118o H 118o H O 118o 124o 122o CH3 H3C O O 116o 122o CH3 δ- δ+ R R Chem 1AA3 147 49
  • 50. Synthesis and reactions of aldehydes and ketones Section 26-5, 26-6 Synthesis Oxidation of alcohols: [O] O OH H [O] OH O Oxidation: Addition of an oxygen atom or removal of (a molecule of) hydrogen [O] = Oxidizing agent Chem 1AA3 149 Primary, Secondary & Tertiary Alcohols R CH2 OH Primary (1o) R CH OH R' Secondary (2o) R'' R C R' OH Tertiary (3o) Chem 1AA3 150 50
  • 51. Oxidation • Primary alcohol acid aldehyde carboxylic O OH O H • Secondary alcohol ketone O OH • Tertiary alcohol OH no reaction – a C-C bond would have to break in order for oxidation to occur Chem 151 1AA3 PH Formative iClicker Question #4 What is the expected product of oxidation of 2,2-dimethylpropanol? (a) (b) (c) (d) 2,2-dimethylpropanoic acid 2,2-dimethylpropanone 2-methyl-2-propanal no reaction Chem 1AA3 152 PB Formative iClicker Question #4 What is the expected product of oxidation of s-pentanol? (a) (b) (c) (d) methyl butyl ketone 2-pentanone pentanoic acid none of the above Chem 1AA3 153 51
  • 52. JV Formative iClicker Question #4 What is the expected product of oxidation of isopentanol? (a) (b) (c) (d) methyl butyl ketone 2-pentanone 4-methyl pentanoic acid none of the above Chem 1AA3 154 HS Formative iClicker Question #4 What is the expected product of oxidation of 2-methylbutanol? (a) (b) (c) (d) 2-methylbutanoic acid 2-methylbutanone s-pentanoic acid none of the above Chem 1AA3 155 Oxidizing Agents • Commonly metals in high oxidation states (transfer of 2 to 4 electrons) e.g., MnO4-, Cr2O72- (KMnO4, K2Cr2O7) • Usually done in acid or base to facilitate electron transfer • Pyridinium chlorochromate (PCC) – Specific for oxidizing 1o alcohols aldehydes Chem 1AA3 156 52
  • 53. Metabolism of Alcohol: Detoxification Enzymatic Detoxification by Two-step Oxidation ethanol rapidly distributes from blood to tissues/organs two-step oxidation of ethanol acetaldehyde brain acetic acid acetic acid is eliminated by kidneys or metabolized into energy "One of the disadvantages of wine is that it makes a man mistake words for thoughts." -- Samuel Johnson Chem 1AA3 157 Metabolism of Alcohol: Detoxification Enzymatic Detoxification by Two-step Oxidation toxic intermediate oxidizing agent Alcohol Dehydrogenase + OH + NAD O H O H Acetaldehyde Dehydrogenase + NAD+ + NADH + H+ O OH + NADH + H+ non-toxic final product Chem 1AA3 158 Addition Reactions to the Carbonyl Group Reduction: NaBH4 is a source of H- (hydride) O 1. NaBH4 H OH 2. H3O+ 1o alcohol aldehyde O ketone p. 1096 1. NaBH4 OH 2. H3O+ 2o alcohol Chem 1AA3 159 53
  • 54. Synthesis and Reactions of Carboxylic Acids and Derivatives Section 26-7 Examples Chem 1AA3 p. 1097 161 Chem 1AA3 162 Carboxylic Acid: Structure 54
  • 55. Synthesis and Reactivity Section 26-7 Carboxylic acids Weak acids: O O + H2O + H2O NaOH OH O Ka = 1.4x10−5 H3O+ + O- O OH O- + + Na+ H3O 2O + H Derivatives: O O R Cl R Acid chloride O O O R R Anhydride O O R R NHR Amide Ester Chem 1AA3 164 Preparation of Esters O + OH H+ CH3CH2OH • Fischer O OCH2CH3 + H2O Esterification • Acid catalyst • Condensation reaction p. 1098 Chem 1AA3 165 55
  • 56. Hydrolysis of Esters O OCH2CH3 + O H+ H2O + CH3CH2OH OH • Reverse of previous reaction • Also requires acid catalyst Chem 1AA3 166 Acid chlorides O Carboxylic acid R Acid chloride O R NH2 R OH O O R Acid-base reaction + O- H3N R + Cl R NH2 R + HCl + HCl NH R amide O R O Cl + R OH R O R ester Chem 1AA3 167 Chem 1AA3 168 Acetyl Group p. 1097 56
  • 57. Synthesis Section 26-12 Concept Check: Synthesis Fill in the missing reagents: O OH Chem 1AA3 170 Chem 1AA3 171 Concept Check: Solution O 1. NaBH4 OH conc. H2SO4, ∆ 2. H3O+ 57
  • 58. PH Formative iClicker Question #4 What are conditions i and ii? i OH O ii i ii (a) Lindlar's catalyst KMnO4 (b) PCC 10% H2SO4 (c) NaBH4 KMnO4 (d) NaBH4 PCC Chem 1AA3 172 PB Formative iClicker Question #4 i What are conditions i and ii? OH ii i ii 10% H2SO4 conc. H2SO4 (b) PCC 10% H2SO4 (c) 10% H2SO4 H2/Pd-C (d) conc. H2SO4 10% H2SO4 (a) Chem 1AA3 173 JV Formative iClicker Question #4 What are conditions i and ii? i ii Cl i ii (a) PCC Cl2 (b) H2/Pd-C HCl (c) H2/Pd-C Cl2 (d) Lindlar's catalyst HCl Chem 1AA3 174 58
  • 59. HS Formative iClicker Question #4 What are conditions i and ii? i ii i ii (a) H2/Pd-C PCC (b) KMnO4 PCC (c) H2/Pd-C Lindlar's catalyst (d) Lindlar's catalyst H2/Pd Chem 1AA3 175 Substitution Reactions and Mechanisms Section 26-11 Chemical Reactions • Charge attraction draws molecules together • In organic chemistry, there is often not a cation reacting with an anion • It is more common to have a charged reagent be attracted to an organic compound that has a dipole – e.g., NaCN + acetone (polarized C=O bond generating an electropositive carbon atom that attracts the CN-) Chem 1AA3 177 59
  • 60. Chemical Reactions Continued • The reagent does not necessarily need to be charged: Lone electron pairs would also be attracted to a dipole Chem 1AA3 178 Chem 1AA3 179 Chemical Reactions • The majority of reactions in organic chemistry involve the flow of electrons from one molecule to another • nucleophile (nucleus loving) = electron donor = Lewis base • electrophile (electron loving) = electron acceptor = Lewis acid p. 1108 Chemical Reactions • In most organic reactions the orbitals of the nucleophile and electrophile are directional therefore the two orbitals must be correctly aligned for a reaction to occur Chem 1AA3 180 60
  • 61. Substitution Reactions at sp3 Hybridized Carbon Charged nucleophiles Neutral nucleophiles Chem 1AA3 181 Mechanism • The flow of electrons between a nucleophile and electrophile can be represented by a double-headed curly arrow NH3 E+ • The result of the movement is to form a bond between an electrophile and a nucleophile NH3 H + H N E H E+ Chem 1AA3 182 Mechanism (continued) • The arrow tail starts at the source of the moving electrons and the arrow head indicates its final destination NH3 E+ Chem 1AA3 183 61
  • 62. SN2 Mechanism S = substitution; N = nucleophilic, 2 = bimolecular Rate = k[OH-][CH3Cl] p. 1111 Chem 1AA3 184 PH Diagnostic iClicker Question What are the nucleophile and the electrophile in this reaction? CH3Cl + Br- Cl- + CH3Br Nucleophile Electrophile (a) Cl- CH3Br (b) CH3Br Cl- (c) Cl- Br- (d) Br- CH3Cl Chem 1AA3 185 PB Diagnostic iClicker Question What are the nucleophile and the electrophile in this reaction? H3C-NH2 + CH3Cl H3C-NH-CH3 + HCl Nucleophile Electrophile (a) CH3Cl H3C-NH-CH3 (b) CH3NH2 CH3Cl (c) CH3NH2 Cl- (d) Cl- H+ Chem 1AA3 186 62
  • 63. JV Diagnostic iClicker Question What are the nucleophile and the electrophile in this reaction? H3C-NH-CH3 + HCl H3C-NH2 + CH3Cl Nucleophile Electrophile (a) CH3NH2 H3C-NH-CH3 (b) CH3Cl Cl- (c) CH3NH2 CH3Cl (d) H3C-NH-CH3 H+ Chem 1AA3 187 HS Diagnostic iClicker Question What are the nucleophile and the electrophile in this reaction? CH3Cl + Br- Cl- + CH3Br Nucleophile Electrophile (a) Cl- Br- (b) CH3Cl Cl- (c) Cl- CH3Cl (d) Br- ClChem 1AA3 188 Chem 1AA3 189 SN2 Mechanism δ- δ- More on mechanisms in the next section 63
  • 64. SN2: Inversion of Configuration Chem 1AA3 190 Chem 1AA3 191 SN1 Mechanism (unimolecular) p. 1112 slow SN1 Mechanism t fas t fas Rate = k [(CH3)3CBr] Chem 1AA3 192 64
  • 65. SN1 versus SN2 • The mechanism depends on many factors, but as a general rule of thumb: • 1o electrophile = SN2 – less stable carbocation intermediate, less steric hindrance to nucleophilic attack • 2o electrophile = ? – hard to predict (you will see this next year) • 3o electrophile = SN1 – more stable carbocation intermediate, more steric hindrance to nucleophilic attack Chem 1AA3 193 PH Formative iClicker Question #5 Rank the likelihood of the following compounds to undergo SN2 nucleophilic substitutions: Cl Cl Cl i (a) (b) (c) (d) i i i i < > > ≈ ii ii ii ii ≈ > ≈ > ii iii iii iii iii iii Chem 1AA3 194 PB Formative iClicker Question #5 Rank the likelihood of the following compounds to undergo SN2 nucleophilic substitutions: i (a) (b) (c) (d) iii i i ii ≈ ≈ > > ii ii iii i ii < > > < Cl Cl Cl iii i iii ii iii Chem 1AA3 195 65
  • 66. JV Formative iClicker Question #5 Rank the likelihood of the following compounds to undergo SN2 nucleophilic substitutions: Cl Cl i (a) (b) (c) (d) iii i i ii ≈ ≈ > > ii ii ii i Cl ii > > ≈ < iii i iii iii iii Chem 1AA3 196 HS Formative iClicker Question #5 Rank the likelihood of the following compounds to undergo SN2 nucleophilic substitutions: Cl Cl Cl i (a) (b) (c) (d) i i i ii ≈ ≈ < ≈ iii ii ii i ii < < > > iii ii iii iii iii Chem 1AA3 197 66

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