Overlap of sp 3 orbitals from carbon and 1s orbitals from hydrogen 1095 o 82 82

Overlap of sp 3 orbitals from carbon and 1s orbitals

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Overlap of sp3 orbitals from carbon and 1s-orbitals from hydrogen109.5o8282Chem1AA3Diagnostic iClicker QuestionHow many σ-bonds are there in this molecule?(a)(b)(c)(d)PH83Chem1AA3Diagnostic iClicker QuestionHow many sp3-orbitals are there in this molecule?(a)(b)(c)(d)HPB84Chem1AA3Diagnostic iClicker QuestionHow many sp3-sp3σ-bonds are there in this molecule?(a)(b)(c)(d)JV
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CO CO
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1) Functional group interconversion – ex. Converting an aldehyde to an alcohol 2) Carbon-carbon bond forming reactions – ex. Grignard reaction
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1 Alkenes Section 26-3 98 Chem 1AA3 Alkenes (C n H 2n ) 99 99 Chem 1AA3 Multiple Covalent Bonds Ethylene has a double bond in its Lewis structure VSEPR says trigonal planar shape at C sp 2 hybridization p. 435 100 100 Chem 1AA3 sp 2 Hybrid Orbitals (section 11-4) Combine one Æ three sp 2 orbitals Hybrid orbital lobes pointing in the direction of an equilateral triangle: bond angles 120 101 Chem 1AA3 sp 2 Hybrid Orbitals 102 Chem 1AA3 sp 2 Hybrid Orbitals The extra p-orbital can be used to form π - bonds π -bonds are covalent bonds that form by the sideways overlap of parallel p-orbitals
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1 103 Chem 1AA3 Ethene Section 11-4 104 Chem 1AA3 Recall: Conformations of alkanes 105 105 Chem 1AA3 Alkenes have restricted rotation p. 1086 106 106 Chem 1AA3 Fats and Oils: Triacylglycerols O O O O R R O O R triacylglycerol Fat: solid at room temp. Oil: liquid at room temp. Key Factors: • Chain length (MW) • Number of double bonds • Geometry of the double OH OH OH glycerol (More information available on p. 1137-1139) 107 Chem 1AA3 Concept Check Which of these two fatty acids has the higher melting point and why? RO O Linoleic acid (R = H) RO O Stearic acid (R = H) 108 Chem 1AA3 Concept Check: Solution RO O Linoleic acid (R = H) RO O Stearic acid (R = H) Straight chain allows more efficient packing, therefore stronger
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1 109 Chem 1AA3 Impact of Geometry 110 Chem 1AA3 The E,Z System of Nomenclature Need a new system • Higher priority Æ higher atomic number p. 1106 111 111 Chem 1AA3 Concept Check O Me 2 N O Me 2 N Label the tamoxifen isomers as E or Z : 112 112 Chem 1AA3 Formative iClicker Question #2 Which molecule has an configuration? (a) (b) (c) (d) (e) PH 113 Chem 1AA3 Formative iClicker Question #2 Which molecule has an configuration? (a) (b) (c) (d) (e) PB 114 Chem 1AA3 Formative iClicker Question #2 Which molecule has an configuration? (a) (b) (c) (d) (e) JV
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2 115 Chem 1AA3 Formative iClicker Question #2 Which molecule has an configuration? (a) (b) (c) (d) (e) HS 116 Chem 1AA3 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: 117 117 Chem 1AA3 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 (2 nd year) 118 118 Chem 1AA3 Diagnostic iClicker Question Which molecule has the highest degree of unsaturation? (a) (b) (c) PH 119 Chem 1AA3 Diagnostic iClicker Question Which molecule has the highest degree of unsaturation? (a) (b) (c) PB 120 Chem 1AA3 Diagnostic iClicker Question Which molecule has the lowest degree of unsaturation? (a) (b) (c) JV
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2 121 Chem 1AA3 Diagnostic iClicker Question Which molecule has the lowest degree of unsaturation? HS (a) (b) (c) Reactions involving alkenes Section 26-3 123 123 Chem 1AA3 Addition Reactions Markovnikov’s rule: the p. 1087-1088 124 124 Chem 1AA3 Explanation of Markovnikov’s rule 2 o carbocation - less stable 3 o carbocation - more stable X haloalkane product 125 Chem 1AA3 Curly arrows The curly arrow represents electrons moving from the alkene π -bond to the proton of HBr, forming a C-H bond. We will examine this in more detail in nucleophilic substitution reactions (Section 26-11) 126 Chem 1AA3 Carbocation stability Stability: Why do alkyl substituents increase cation stability? Steric: The cationic carbon rehybridizes from sp methyl < < < Br H 3 C H 3 C CH 3 Br - CH 3 H 3 C H 3 C
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2 127 Chem 1AA3 Carbocation stability Why do alkyl substituents increase cation stability? Electronic: Alkyl substituents are electron donating compared with H. Donating electrons to an electron deficient (positively charged) centre stabilizes it. = a permanent electric dipole δ - δ + 128 Chem 1AA3 Formative iClicker Question #3 What is the expected product, according to Markovnikov's rule? (a) (b) (c) (d) PH 129 129 Chem 1AA3 Formative iClicker Question #3 What is the expected product, according to Markovnikov's rule? (a) (b) (c) (d) PB 130 130 Chem 1AA3 Formative iClicker Question #3 What is the expected product, according to Markovnikov's rule? (a) (b) (c) (d) JV 131 Chem 1AA3 Formative iClicker Question #3 What is the expected product, according to Markovnikov's rule? (a) (b) (c) (d) HS 132 Chem 1AA3 Hydration Reaction • Addition is favoured (forward reaction) in dilute acid • Elimination is favoured (reverse reaction) in concentrated acid
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2 133 Chem 1AA3 Hydration also follows Markovnikov's rule 134 Chem 1AA3 Reduction of Alkenes H H catalyst Hydrogenation 135 135 Chem 1AA3 Application: Hydrogenation of Natural Products CH 2 OC(CH 2 ) 7 CH CHOC(CH 2 ) 7 CH O CH(CH 2 ) 7 CH 3 CH(CH 2 ) 7 CH 3 O CH 2 OC(CH 2 ) 7 CH O CH(CH 2 ) 7 CH 3 CH 2 OC(CH 2 ) 16 CH 3 CHOC(CH 2 ) 16 CH 3 O O CH 2 OC(CH 2 ) 16 CH 3 O (More information available on p. 1137-1139) 136 136 Chem 1AA3 Partial Hydrogenation RO O RO O H H 137 Chem 1AA3 cis versus trans fatty acids Alkynes Section 26-3
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2 139 Chem 1AA3 Alkynes According to VSEPR, alkynes are linear p. 1085 140 Chem 1AA3 sp Hybrid Orbitals Combine one Æ two sp orbitals Section 11-4, p. 436 141 141 Chem 1AA3 sp Hybrid Orbitals 142 142 Chem 1AA3 Acetylene: Orbitals Acetylene, C 2 H 2 , has a triple bond. Linear at carbon Reactions of Alkynes 144 Chem 1AA3 Reduction of Alkenes and Alkynes H H H H catalyst CH 3 CH 2 C CCH 3 + H 2 Lindlar's catalyst CH 3 CH 2 C CCH 3 + H 2 Pd/C p. 1088
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2 The Carbonyl Group: ketones and aldehydes Section 26-6 146 Chem 1AA3 Examples Ketones Aldehydes O Acetone Methyl ethyl ketone (MEK) Testosterone O OH CH 3 H 3 C O H O H O H H O Formaldehyde Benzaldehyde Cinnamaldehyde p. 1094-1095 147 147 Chem 1AA3 Structure and Polarity H 3 C CH 3 O 122 o 116 o 122 o H CH 3 O 124 o 118 o 118 o H H O 121 o 118 o 121 o Synthesis and reactions of aldehydes and ketones Section 26-5, 26-6 149 Chem 1AA3 Synthesis Oxidation of alcohols: OH OH Oxidation: Addition of an oxygen atom or removal of (a molecule of) hydrogen [O] = Oxidizing agent [O] [O] 150 Chem 1AA3 Primary, Secondary & Tertiary Alcohols Primary (1 o ) Secondary (2 o ) Tertiary (3 o )
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2 151 Chem 1AA3 Oxidation Primary alcohol Æ Secondary alcohol Æ Tertiary alcohol Æ – a C-C bond would have to break in order for oxidation to occur 152 Chem 1AA3 Formative iClicker Question #4 What is the expected product of oxidation of (a) (b) 2,2-dimethylpropanone (c) 2-methyl-2-propanal (d) PH 153 153 Chem 1AA3 Formative iClicker Question #4 What is the expected product of oxidation of (a) (b) 2-pentanone (c) (d) PB 154 154 Chem 1AA3 Formative iClicker Question #4 What is the expected product of oxidation of (a) (b) 2-pentanone (c) (d) JV 155 Chem 1AA3 Formative iClicker Question #4 What is the expected product of oxidation of (a) (b) 2-methylbutanone (c) s (d) HS 156 Chem 1AA3 Oxidizing Agents Commonly metals in high oxidation states (transfer of 2 to 4 electrons) e.g., MnO 4 - , Cr 2 O 7 2-
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2 157 Chem 1AA3 Metabolism of Alcohol: Detoxification ethanol rapidly distributes from blood to tissues/organs Æ brain two-step oxidation of ethanol Æ acetic acid is eliminated by kidneys or metabolized into energy Enzymatic Detoxification by Two-step Oxidation "One of the disadvantages of wine is that it makes a man mistake words for thoughts." -- Samuel Johnson 158 Chem 1AA3 Metabolism of Alcohol: Detoxification Enzymatic Detoxification by Two-step Oxidation Alcohol Dehydrogenase Acetaldehyde Dehydrogenase + NAD + + NADH + H + + NAD + + NADH + H + oxidizing agent toxic intermediate non-toxic final product 159 159 Chem 1AA3 Addition Reactions to the Carbonyl Group Reduction: NaBH 4 is a source of H - (hydride) H O O aldehyde ketone p. 1096 Synthesis and Reactions of Carboxylic Acids and Derivatives Section 26-7 161 Chem 1AA3 Examples p. 1097 162 Chem 1AA3 Carboxylic Acid: Structure
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2 Synthesis and Reactivity Section 26-7 164 Chem 1AA3 Carboxylic acids Weak acids: OH O + H 2 O OH O + NaOH Acid chloride Ester Amide Anhydride Derivatives: 165 165 Chem 1AA3 Preparation of Esters OH O + CH 3 CH 2 OH • Acid catalyst • Condensation reaction p. 1098 166 166 Chem 1AA3 Hydrolysis of Esters OCH 2 CH 3 O + H 2 O • Reverse of previous reaction • Also requires acid catalyst 167 Chem 1AA3 Acid chlorides Acid chloride R Cl O R NH 2 + R Cl O R OH + R OH O R NH 2 Carboxylic acid amide ester 168 Chem 1AA3 Acetyl Group p. 1097
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2 Synthesis Section 26-12 170 Chem 1AA3 Concept Check: Synthesis Fill in the missing reagents: OH O 171 171 Chem 1AA3 Concept Check: Solution 172 172 Chem 1AA3 Formative iClicker Question #4 What are conditions i and ii ? i ii PH (d) (c) (b) (a) ii i 173 Chem 1AA3 Formative iClicker Question #4 What are conditions i and ii ? i ii PB (d) (c) (b) (a) ii i 174 Chem 1AA3 Formative iClicker Question #4 What are conditions i and ii ? i ii JV (d) (c) (b) (a) ii i
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3 175 Chem 1AA3 Formative iClicker Question #4 What are conditions i and ii ? i ii HS (d) (c) (b) (a) ii i Substitution Reactions and Mechanisms Section 26-11 177 177 Chem 1AA3 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 - ) 178 178 Chem 1AA3 Chemical Reactions Continued The reagent does not necessarily need to be charged: Lone electron pairs would also be attracted to a dipole 179 Chem 1AA3 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 180 Chem 1AA3 Chemical Reactions In most organic reactions the orbitals of the nucleophile and electrophile are directional Æ therefore the two orbitals must be correctly aligned for a reaction to occur
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3 181 Chem 1AA3 Substitution Reactions at sp 3 Hybridized Carbon Charged nucleophiles Neutral nucleophiles 182 Chem 1AA3 Mechanism The flow of electrons between a nucleophile and electrophile can be represented by a double-headed curly arrow The result of the movement is to form a bond between an electrophile and a nucleophile 183 183 Chem 1AA3 Mechanism (continued) The arrow tail starts at the source of the moving electrons and the arrow head indicates its final destination 184 184 Chem 1AA3 S N 2 Mechanism S = substitution; N = nucleophilic, 2 = bimolecular p. 1111 185 Chem 1AA3 Diagnostic iClicker Question (d) (c) (b) (a) Electrophile Nucleophile PH What are the nucleophile and the electrophile in this reaction? 186 Chem 1AA3 PB Diagnostic iClicker Question (d) (c) (b) (a) Electrophile Nucleophile What are the nucleophile and the electrophile in this reaction?
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3 187 Chem 1AA3 JV Diagnostic iClicker Question What are the nucleophile and the electrophile in this reaction? (d) (c) (b) (a) Electrophile Nucleophile 188 Chem 1AA3 HS Diagnostic iClicker Question What are the nucleophile and the electrophile in this reaction? (d) (c) (b) (a) Electrophile Nucleophile 189 189 Chem 1AA3 S N 2 Mechanism More on mechanisms in the next section δ - δ - 190 190 Chem 1AA3 S N 2: Inversion of Configuration 191 Chem 1AA3 S N 1 Mechanism (unimolecular) p. 1112 192 Chem 1AA3 S N 1 Mechanism sl ow fast fast
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3 193 Chem 1AA3 S N 1 versus S N 2 The mechanism depends on many factors, but as a general rule of thumb: • 1 o electrophile = S – less stable carbocation intermediate, less steric hindrance to nucleophilic attack • 2 o electrophile = ? – hard to predict (you will see this next year) • 3 o electrophile = S – more stable carbocation intermediate, more steric hindrance to nucleophilic attack 194 Chem 1AA3 Formative iClicker Question #5 Rank the likelihood of the following compounds to undergo S N 2 nucleophilic substitutions: (a) (b) (c) (d) PH 195 195 Chem 1AA3 Formative iClicker Question #5 Rank the likelihood of the following compounds to undergo S N 2 nucleophilic substitutions: (a) (b) (c) (d) PB 196 196 Chem 1AA3 Formative iClicker Question #5 Rank the likelihood of the following compounds to undergo S N 2 nucleophilic substitutions: (a) (b) (c) (d) JV 197 Chem 1AA3 Formative iClicker Question #5 Rank the likelihood of the following compounds to undergo S N 2 nucleophilic substitutions: (a) (b) (c) (d) HS
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  • Organic chemistry, Chem, Carboxylic acid, H H H H H C C C C C H H H H H H 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

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