65 65 Chem 1AA3 Bonding methane Overlap of sp 3 orbitals from carbon and 1s

65 65 chem 1aa3 bonding methane overlap of sp 3

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1) Functional group interconversion – ex. converting an aldehyde to an alcohol 2) Carbon-carbon bond forming reactions
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Alkenes Section 26-3 74 Chem 1AA3 Alkenes (C n H 2n ) 75 75 Chem 1AA3 Multiple Covalent Bonds Ethylene has a double bond in its Lewis structure VSEPR says trigonal planar at carbon 76 76 Chem 1AA3 sp 2 Hybrid Orbitals Combine one 2s orbital + two 2p orbitals ! Hybrid orbital lobes pointing in the direction of an equilateral triangle: bond angles 120 o
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77 77 Chem 1AA3 sp 2 Hybrid Orbitals 78 Chem 1AA3 sp 2 Hybrid Orbitals (section 11-4) The extra p-orbital can be used to form " - bonds " -bonds are covalent bonds that form by the sideways overlap of parallel p-orbitals 79 79 Chem 1AA3 Ethene Section 11-4 80 80 Chem 1AA3 Recall: Conformations of alkanes
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81 81 Chem 1AA3 Alkenes have restricted rotation Geometric Isomers 82 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. OH OH OH glycerol 83 83 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) 84 84 Chem 1AA3 Solution RO O Linoleic acid (R = H) RO O Stearic acid (R = H)
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85 85 Chem 1AA3 Impact of Geometry 86 Chem 1AA3 The E,Z System of Nomenclature 87 87 Chem 1AA3 Concept Check O Me 2 N O Me 2 N Label the isomers as E or Z: Reactions involving alkenes Section 26-3
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89 89 Chem 1AA3 Addition Reactions Markovnikov’s rule: 90 Chem 1AA3 Concept Check HBr Draw the product expected, according to Markovnikov’s rule 91 91 Chem 1AA3 Concept Check 92 92 Chem 1AA3 Hydration Reaction • Addition is favored (forward reaction) in dilute acid • Elimination is favored (reverse reaction) in concentrated acid
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93 93 Chem 1AA3 Reduction of Alkenes H H catalyst Hydrogenation 94 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 3H 2 Ni catalyst heat 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 Unsaturated vegetable oil (olein-liquid) Solid cooking fat-shortening (stearin, solid) 95 95 Chem 1AA3 Partial Hydrogenation RO O RO O H 2 (1 equiv.) catalyst H H mixture saturated at either double bond, e.g. 96 96 Chem 1AA3 cis versus trans Cis -9-octadecenoic acid (Oleic acid) Trans -9-octadecenoic acid (Elaidic acid)
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Alkynes Section 26-3 98 Chem 1AA3 Alkynes 99 99 Chem 1AA3 sp Hybrid Orbitals Combine one 2s orbital + one 2p orbital ! two sp orbitals (+ two 2p orbitals left over) Section 11-3 100 100 Chem 1AA3 sp Hybrid Orbitals
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101 Chem 1AA3 Acetylene: Orbitals Acetylene, C 2 H 2 , has a triple bond. Linear at carbon Reactions of Alkynes 103 103 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 The Carbonyl Group: ketones and aldehydes Section 26-6
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105 Chem 1AA3 Examples Ketones Aldehydes O O OH CH 3 H 3 C O H O H O H H O 106 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, 26-6 108 108 Chem 1AA3 Synthesis Oxidation of alcohols: OH OH Oxidation: [O] = Oxidizing agent [O] [O]
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109 Chem 1AA3 Primary, Secondary & Tertiary Alchols R CH 2 OH R CH OH R' R C OH R' R'' 110 Chem 1AA3 Oxidation Primary alcohol ! aldehyde ! carboxylic acid Secondary alcohol ! ketone 111 111 Chem 1AA3 Concept Check What would you expect the product to be for the oxidation of tertiary (3 o ) alcohols, e.g. tert -butanol? CH 3 H 3 C CH 3 OH Tertiary alcohols tend not to react, as a carbon-carbon bond would have to be broken in order for the oxidation to occur. 112 112 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- (KMnO 4 , K 2 Cr 2 O 7 ) Usually done in acid or base to facilitate electron transfer Pyridinium chlorochromate (PCC)
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113 Chem 1AA3 Addition Reactions to the Carbonyl Group Reduction: NaBH 4 is a source of H - (hydride) H O 1. NaBH 4 2. H 3 O + O 1. NaBH 4 2. H 3 O + Aldehyde ketone Synthesis and Reactions of Carboxylic Acids and Derivatives Section 26-7 115 115 Chem 1AA3 Examples 116 116 Chem 1AA3 Carboxylic Acid: Structure
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Synthesis and Reactivity Section 26-7 118 Chem 1AA3 Carboxylic acids Weak acids: Derivatives: OH O + H 2 O R Cl O R O O R R NHR O R O O R O OH O + H 2 O NaOH 119 119 Chem 1AA3 Preparation of Esters OH O H + + CH 3 CH 2 OH 120 120 Chem 1AA3 Hydrolysis of Esters OCH 2 CH 3 O H + + H 2 O
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121 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 122 Chem 1AA3 Acetyl Group Synthesis Section 26-12 124 124 Chem 1AA3 Concept Check: Synthesis Fill in the missing reagents: OH O
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125 Chem 1AA3 Solutions Substitution Reactions and Mechanisms Section 26-11 127 127 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 128 128 Chem 1AA3 Chemical Reactions Continued The reagent does not necessarily need to be charged:
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129 Chem 1AA3 Chemical Reactions The majority of reactions in organic chemistry involve the flow of electrons from one molecule to another nucleophile (nucleus loving) electrophile (electron loving) 130 Chem 1AA3 Chemical Reactions In most organic reactions the orbitals of the nucleophile and electrophile are directional ! 131 131 Chem 1AA3 Substitution Reactions at sp 3 Hybridized Carbon Charged nucleophiles Neutral nucleophiles 132 132 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
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133 Chem 1AA3 Mechanism (continued) NH 3 E + 134 Chem 1AA3 Concept Check Na + OH - + CH 3 Cl CH 3 OH + NaCl Which species is the nucleophile? Which species is the electrophile? Draw the mechanism of the reaction? 135 135 Chem 1AA3 S N 2 Mechanism S = substitution; N = nucleophilic, 2 = bimolecular 136 136 Chem 1AA3 S N 2 Mechanism More on mechanisms in the next sections
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137 Chem 1AA3 S N 2: Inversion of Configuration 138 Chem 1AA3 S N 1 Mechanism (unimolecular) 139 139 Chem 1AA3 S N 1 Mechanism Rate = k [(CH 3 ) 3 CBr] slow fast fast Stereoisomers Section 26-10
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141 Chem 1AA3 Chirality Stereoisomers: Same molecular formula and connectivity of atoms but – - cis/trans (E/Z) - R and S 142 Chem 1AA3 Chiral Compounds Structures are chiral if they cannot be superimposed upon their mirror image Achiral compounds can be superimposed upon their mirror images 143 143 Chem 1AA3 Chirality 144 144 Chem 1AA3 Stereogenic Centers
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