Lesson18 - 1) Acid-Base - hydrogen swap Classes of Chemical...

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Unformatted text preview: 1) Acid-Base - hydrogen swap Classes of Chemical Transformations This page summarizes the main classes of chemical transformations. The purpose of presenting this overview is to provide an organizational framework as an outline of upcoming studies. In learning new reactions you will benefit from recognizing to which of the seven classes the new reaction belongs. 2 & 3) Oxidation & Reduction 4) Substitution- replace Cs substituent (-X) with another (-Y), neither being -H X C Y C Y + X + neither X nor Y being hydrogen Y replaces X 5) Elimination- loss of XY elements with concomitant pi bond formation 6) Addition- gain of XY elements with concomitant loss of pi bond reduction X C H C oxidation H replaces X X replaces H change in the number of C-H bonds in relation to the number of C-X bonds X C Z Z Y C + X Y elimination addition form bond-XY break bond +XY base H X H Y Y + X + base acid acid 7) Rearrangement- isomerization process (no atoms lost or gained); results in new bonding connectivity (one of many examples shown as there is no generic representation). R CH 3 R R stands for a generic "residue" Z = C, N, O Substitution at sp 3 Carbon: Examples Nu + CH 3 Br CH 3 Nu Br + Substitution at sp 3 Carbon: Examples Nu + CH 3 Br CH 3 Nu Br + Substitution at sp 3 Carbon: More Examples Nu + CH 3 Br CH 3 Nu Br + Substitution Mechanisms Require New Elementary Steps: Nucleophile Dissociation [D N ] & the Nature of Leaving Groups Empty a Filled [D N ] involves sigma bond breaking n a a filled empty n n a n a Curved Arrows Imply the Frontier Orbitals Curved arrows indicate the HOMO-LUMO pair (Frontier Orbitals) involved in an elementary step. The tail of the arrow implies the filled orbital (HOMO) is electron pair. The head of the arrow points to an atom on the leaving group (L) suggesting that an atom-centered empty orbital (LUMO, a ) accepts the electron pair. The process produces no new bonding interactions. A good leaving group will have a high energy and low lying a . [D N ] This symbol means a dissociation of a nucleophile [D N ] involves a a no-bond interaction C L C L +-L is the leaving group Substitution Mechanisms Require New Elementary Steps: Nucleophile Association [A N ] Empty a Filled n [A N ] involves sigma bond making n a a filled...
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This note was uploaded on 01/25/2012 for the course CHEM 232 taught by Professor Miller during the Spring '08 term at University of Illinois, Urbana Champaign.

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Lesson18 - 1) Acid-Base - hydrogen swap Classes of Chemical...

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