13 SN2 BIMOLECULARBimolecular simply refers to the rate depending on BOTH reactants because of the nature of the mechanismRate = k[RX][Nu]Rate depends on both because there isONE SINGLE COLLISION BETWEEN RX and Nu to form a Nu-R-X transition state
14 SN2 BIMOLECULAR 100% INVERSION OF STEREOCHEMISTRY OCCURS! SUBSTRATE LEAVING GROUP
15 Factors that affect SN2 RXNS: STERIC EFFECTS TO INCOMING Nu:C=C-X (vinylic) and Ar-X (aryl) TOTALL UNREACTIVE
17 Factors that affect SN2 RXNS: THE LEAVING GROUPshould be stable on its own as a free anionComparing halides, we go down the column
18 Factors that affect SN2 RXNS: Alcohols and fluorides usually do not undergo SN2 because OH- and F- aren’t good leaving groupsThis is why we use SOCl2 and PBr3 … THEY CONVERT THE –OH INTO A BETTER LEAVING GROUP
19 Factors that affect SN2 RXNS: Reaction SOLVENT can also affect the reaction.We prefer POLAR APROTIC SOLVENTSPOLAR but no –OH or –NH in the molecule (no H2O, NH3, etc…)Polar protic solvents form a CAGE around Nu
24 SN1 UNIMOLECULARUnimolecular: rate depends only on the substrate (mechanism), almost opposite of SN2Rate = k[RX]Rate is only dependent on the slowest step which is the spontaneous dissociation of your leaving group. (molecules just don’t easily dissociate!)
41 Elimination Reactions More compliated (different mechanisms)The loss of H-X can lead to a MIXTURE of alkene products (C-C-X C=C + HX)But we can predict the most stable/major poductZAITZEV’S RULE: base-induced eliminations will form more stable alkene
42 E2 eliminationAgain, bimolecular so a single collision between your Base B: and the alkyl halide.
43 E2 eliminationAnti-periplanar is favored for transition state
44 E2 eliminationAnti-periplanar is favored for transition state
54 E1cBUnimolecular, but this time CARBANION formed because a proton H+ is first removed by a base.cB stands for “conjugate base” because you deprotonate your carbon C-H into a C- and H+Usually favored for poor leaving groups (e.g. –OH)Carbanion can be stabilized with C=O groups nearby
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