Cehm Basics Essay

628 WordsNov 14, 20133 Pages
Organic Chemistry Exam #3 Material Fall 2013 Substitution and Elimination Reactions Naming Alkyl Halides and E/Z Nomenclature SUBSTITUTION REACTIONS “Substrate” = the electrophile (electron loving) (positive charge) - Substrate must contain a leaving group to participate in a sbsitution reaction Alkyl Halides: H bonded to an EN atom (B-, I-, Cl-) Primary Alkyl Halides: One Carbon group attached to center Carbon Secondary Alkyl Halides: 2 Carbons attached to center Carbon Tertiary Alkyl Halide: 3 Carbons attached to center Carbon Quaternary Alkyl Halide: 4 Carbons attached to center Carbon SN2 REACTION - one step Rate= k [substrate][nucleophile] -“bimolecular”- because the rate depends on 2 different compounds *INVERSION OF CONFIGURATION- if the reactant is R, the product will be S *The nucleophile can only attack from the back side -stereospecific reaction- the configuration of the product is dependent on the configuration of the starting material Order of Reactivity for SN2 reactions: 1. Methyl- most reactive because there’s less steric hindrance 2. Primary 3. Secondary 4. Tertiary- too slow to measure because of steric hindrance *STRONG NUCLEOPHILE FAVORS SN2 I- HO- BR- RO- Cl- N=C- HS- H2S RSH *NEED A VERY STRONG LEAVING GROUP; BECAUSE IT LEAVES IN ITS OWN STEP *POLAR APROTIC SOLVENT (contains no hydrogen directly bonded to EN) DMSO DMF CH3CN SN1 REACTION -2 steps: LG leaves (SLOW STEP) then nucleophile attacks (FAST STEP) -step one: Rate determining step because it’s the slowest step Rate= k[substrate] *unimolecular: because the rate is dependent on only one compound *CARBOCATION INTERMEDIATE: must be as stable as possible. -Therefore, SN1 Reactions favor tertiary alkyl halides because more Carbon atoms allows for the delocalization of the charge; making it more stable Order of

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