Superposable Vs. SuperimposableSuperposable Vs. SuperimposableSlide Number 3Slide Number 4Introduction Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 10Slide Number 11Slide Number 12Slide Number 13Slide Number 14Slide Number 15Superposable Vs. Superimposable: Part 2Slide Number 17Bond Breaking and Bond Making ProcessSlide Number 19Mechanism of the SN2 reactionSlide Number 21Slide Number 22Slide Number 23A Free Energy Diagram for a Hypothetical Reaction with a Positive Free-Energy Change Slide Number 25Temperature & Reaction RateVideo SN2The Stereochemistry of SN2 ReactionsSlide Number 29Slide Number 30Slide Number 31Slide Number 32Mechanism for SN1 Mechanism: Step (1)Slide Number 34Slide Number 35Slide Number 36Video SN1CarbocationsCarbocation StabilityCarbocation StabilityThe Stereochemistry of SN1 ReactionsSlide Number 42Slide Number 43Slide Number 44Slide Number 45Slide Number 46Slide Number 47Slide Number 48Slide Number 49Reactivity of the Substrate in SN1 ReactionsSlide Number 51(3) Solvent Effect in SN1 and SN2 ReactionsClassification of SolventsSlide Number 54Slide Number 55Slide Number 56Slide Number 57Slide Number 58Slide Number 59Slide Number 60Slide Number 61Slide Number 62Slide Number 63Slide Number 64StereochemistrySlide Number 66Elimination Reactions of Alkyl Halides Slide Number 68Slide Number 69Dehydrohalogenation Alkoxide BasesSlide Number 72Slide Number 73Slide Number 74E1 Mechanism: Step (1)E1 Mechanism: Step (2)Slide Number 77Slide Number 78Slide Number 79Slide Number 80Slide Number 81Basicity vs. NucleophilicitySlide Number 83SummarySlide Number 85REVIEWSlide Number 87Slide Number 88Slide Number 89Slide Number 90Slide Number 91Slide Number 92Slide Number 93Slide Number 94Slide Number 95Slide Number 96Slide Number 97Slide Number 98Slide Number 99Slide Number 100Slide Number 101Slide Number 102Slide Number 103Superposable Vs. Superimposable • Textbook: Many object are achiral. By this, we mean that the object and its mirror image are identical—the object and its mirror image are superposable. Footnote: superimposable different from superposable. Superposable infers that all part of the object coincide. Question 126: An achiral molecule is one that is [superimposable or superposable] upon its mirror image? 1 su·per·im·pose verb (used with object), su·per·im·posed, su·per·im·pos·ing. 1. to impose, place, or set over, above, or on something else. su·per·pose verb (used with object), su·per·posed, su·per·pos·ing. 1. to place above or upon something else, or one upon another. 2. geometry to transpose (the coordinates of one geometric figure) to coincide with those of another Verb1. superimpose - place on top of; "can you superimpose the two images?“ means lay over, superpose• They are interchangeable. Superposable is a broader term (ability for an object to be placed over another object; without the visibility restriction) while superimposable is the same thing except they have to be done in such a way that both will be visible. 2 Superposable Vs. SuperimposableChapter 6 Ionic Reactions Nucleophilic Substitution and Elimination Reactions of Alkyl Halides 3In this chapter : 1. What groups can be replaced (i.e., substituted) or eliminated 2. The mechanisms by which these processes occur 3. The conditions that can promote these reactions 4The polarity of a carbon-halogen bond leads to the carbon having a partial positive charge. In alkyl halides this polarity causes the carbon to become activated to substitution reactions with nucleophiles. Introduction • Carbon-halogen bonds get longer and weaker in going from fluorine to iodine. 5 Vinyl halides (Alkenyl halides)  Aryl halides  Acetylenic halides (Alkynyl halides) sp2Xsp2Xbenzene or aromatic ringspX6 Structural Types of Organic HalidesH2CCH3Clethyl chlorideCH2HCCH2Clallyl chlorideClphenyl chlorideH2CClbenzyl chloride7 In Class Practice What hybridization are the C indicated by the arrow? (1) sp3 (2)sp2 (3) sp (D) (C) (B) (A)CXsp3δ+δ−Alkyl halides Prone to undergo Nucleophilic Substitutions (SN) and Elimination Reactions (E) (the focus of this Chapter) sp2XX Xsp2sp• Sp2 & sp alkyl halides have different reactivity than alkyl halides, • Do not undergo SN or E reactions 8Nucleophilic Substitution Reactions In these types of reactions a nucleophile (a species with an unshared electron pair) reacts with an electron deficient carbon bearing a leaving group. The leaving group is displaced by a nucleophile and separates from the carbon with its pair of electrons. 9 Nu+C Xδ+δ−CNu+X(nucleophile) (substrate) (product) (leavinggroup)The bond between C and LG breaks, giving both e⊖ from the bond to LG The Nu⊖ uses its e⊖ pair to form a new covalent bond with the substrate C The LG gains the pair of e⊖ originally bonded in the substrate The Nu⊖ donates an e⊖ pair to the substrateNucleophilic Substitution Reactions In these types of reactions a nucleophile (a species with an unshared electron pair) reacts with an electron deficient carbon bearing a leaving group. The leaving group is displaced by a nucleophile and separates from the carbon with its pair of electrons. Examples of nucleophilic substitution: 10 Nu+CXδ+δ−CNu+X(nucleophile) (substrate) (product) (leavinggroup)The nucleophile reacts at the electron deficient (electrophilic) carbon. A nucleophile may be any negative ion or neutral molecule that has at least one unshared electron pair. 11A leaving group is a substituent that can leave as a relatively stable entity with the pair of electrons originally bonding it to carbon. It can leave as an (1) anion or (2) neutral species. 12 (1) (2)To be a good leaving group, the substituent must be able to leave as a relatively stable, weakly basic molecule or ion e.g.: I⊖, Br⊖, Cl⊖, TsO⊖, MsO⊖, H2O, NH3 OMs =OTs =O SOOCH3O SOOCH3(Tosylate)(Mesylate)13In Class Problems: Designate the nucleophile, the electrophile, and the leaving group for each of the following reactions. CH2Cl+KCNCH2CN+KCl(1)OH2C CCH3CH3+CH3ONaH3CO CH2CCH3CH3OH(2)1415 In Class Problems: Designate the nucleophile, the electrophile, and the leaving group for each of the following reactions.• Q 126: Wiley changed the answer to superposable sometime on Thursday • Full credit was given • Exemption policy: “turned in all homework assignments on the designated due dates and has an average score of