End of Chapter 19 Notes (September 28)
End of Chapter 19 Notes (September 28) CHEM-C 342
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This 6 page Class Notes was uploaded by Delaney Crane on Monday September 28, 2015. The Class Notes belongs to CHEM-C 342 at Indiana University taught by Van Nieuwenhze M in Fall 2015. Since its upload, it has received 109 views. For similar materials see ORGANIC CHEMISTRY LECTURES 2 in Chemistry at Indiana University.
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Date Created: 09/28/15
Chapter 19 Nucleophilic Aromatic Substitution o Requires good nucleophile o Requires really good leaving group LG 0 Sometimes called SNAr SNAr Br OH 1NaOH 70 C H 2H3O N02 N02 Br 1NaOH 70 C gt NO RXN 2H3O No2 Nitro group is electron withdrawing and in 2nd example is meta with no reaction Requirements for SNAr 1 Ring must have a good electron withdrawing group EWG 2 Ring must have a good LG 3 LG must be ortho or para to the EWG Mechanism Br Br Br Br Br 1 quotOH o gt 6 4 H N02 N I N O O 0 O 06 o39 6 O Meisenheiser Complex The fourth structure in the Meisenheiser Complex has a significant difference from the others The negative charge is on the O and not the C leading to it being the most stable All the resonance structures are negatively charged I NO N02 The nitro group must be either ortho or para because if it were meta then there wouldn t be the correct resonance structures never get to above structure EliminationAddition CI NaOH Heat NO RXN Cl Cl 1 NaOH 350 C Y I 2H3O NH2 NH 1NaNH2 2 NH31 gt 2H3O How do you get the second product This reaction proceeds by a very different mechanism Cl NH 2 NH 2 1NaNH2 NH3G gt 2H30 50 50 Took the structure and modified it with an isotopic label and found the label to move to 2 different locations on on Benzyne Intermediate with CC triple bond is called benzyne very highly strained BUT this is not a regular CC triple bond because there is still a pi bond in the ring but the other 2 electrons can be thought of in 2 different orbitals 0 Benzyne is very reactive so much so that it can be used as a dienophile Reactions covered in chapter 19 o Electrophilic aromatic substitution sigmacomplex o Nucleophilic aromatic substitution Meisenheimer complex 0 EliminationAddition benzyne