Learning Guide for Chapter 8 - Organic Reactions III. Substitution, Addition, and Elimination ReactionsII. Oxidation and Reduction Reactions III. Radical Reactions IV. Reactive Intermediates V. Stereochemistry of ReactionsI. Substitution, Addition, and Elimination ReactionsIn the previous chapter, we learned to use association, dissociation, and displacement to describe Lewis acid/base reactions. Complete the following reactions.HOH+OHHHOH+dissociationClO+OCl+displacementOH2associationAre these complete reactions?no - reactions usually start and end with neutral moleculesthese are steps in the mechanism of a reactionWhat do the following terms mean?addition:How are they different from the terms above?they refer to the end result of a reaction, not what happens to the electronswhere did the C+ come from?how will this compound become neutral?how did the alcohol become protonated?what will happen to the C+?how did the alcohol get deprotonated?substitution:elimination:a bond to one group is substituted for a bond to another groupnew atoms are added to a molecule, and a double bond is lostatoms are lost from a molecule, and a double bond is gainedLG Ch 8 p 2Match the following reactions with one of the three descriptions on the previous page.ClNaHN2NH3NH2+ NaClsubstitutionH2SO4H2OOHadditionBr(CH3)3COKelimination+ (CH3)3COH + KBrWhich of these involve C=C?addition starts with a C=Celimination ends with a C=CII. Oxidation and Reduction ReactionsHow are oxidation and reduction defined in organic chemistry?oxidation: gaining bonds to O and/or losing bonds to Hreduction: losing bonds to O and/or gaining bonds to HHow is oxidation defined in general chemistry?oxidation - loss of electrons (decrease in charge)reduction - gain of electrons (increase in charge)Ag --> AgO0+2KMnO4 --> MnO2+7+4Why won't this work in organic chemistry?compounds can be oxidized or reduced without changing chargeOHKMnO4H2OMnO2O+Mn was reduced, so theorganic compound musthave been oxidizedoxidation states are more difficult to calculateLG Ch 8 p 3Is only oxygen involved?no - any other atom which is more electronegative than C counts (N, halogens)Which of the following is occurring in each of these transformations?HOOHC loses bonds to O and gains a bond to H reductionOboth C's lose a bond to H and gain a bond to OoxidationOHOHOC gains 2 bonds to Ooxidationboth C's gain a bond to HreductionNO2NH2N loses 3 bonds to O, gains 2 bonds to HreductionWhat are the highest and lowest oxidation states of carbon?lowest - methanehighest - carbon dioxideCH HH HC OOCan atoms other than carbon be oxidized or reduced? yesClnot as common to use these termsC lost a bond to Cl, gained a bond to HreductionOHOHOH HOboth C's gain a bond to Ooxidationcalled oxidative cleavage because a C-C was also brokenAre all reactions oxidation and reductions?no - sometimes the starting material and product are in the same oxidation stateLG Ch 8 p 4OOHHO+OO1st C stays at 3 bonds to O2nd C stays at 1 bond to Ono changeOH1 C gained a bond to O, 1 C gained a bond to Hno net changeBrOHC lost a bond to Br, gained a bond to Oboth are more EN than Cno changeOHOloss of H and change of charge means no change in oxidation stateacid/base reactions are not redox reactionsWhat is an oxidizing agent?a compound which is easily reduced, oxidizes other compoundsWhat are some common oxidizing agents, and how can you recognize them?Na2CrO4sodium chromateKMnO4potassium permanganteH2O2hydrogen peroxideO3ozonemetal atom in a high oxidation state, lots of O'sO bonded to itselfWhat is a reducting agent, and how can you recognize them?a compound which is easily oxidized, reduces other compoundsH2NaBH4LiAlH4NaSnhydrogen gassodium borohydridelithium aluminum hydride (LAH)sodium metaltin metalmetals in elemental statehydride reagents (H bonded to group III atoms)LG Ch 8 p 5III. Radical reactionsWhat is a radical?an atom (or molecule) with an unpaired electronH Ohydroxyl radicalBrbromine radicalcarbon radicalAre radicals very reactive?yes! they have an incomplete octetHow are radicals formed?a molecule with a weak bond absorbs energy from heat or light and breaks homolyticallyBr BrO OBr Br+H3C OCH3O+hv orlighthv orlightWhat kinds of molecules form radicals in this way?molecules with two highly EN and/or large atoms bonded to each otherinitiation stepsHow are carbon radicals formed?Are radicals dangerous?yes - when they are formed inside the body, they can react with proteins and DNA and cause damage to cells; they are thought to play a part in agingHBr+H Br+they react with radicals formed by initiation stepsWhat are reactions like this called?initiation steps - bonds break to form radicalsWhat is this type of reatction called?propogation - one radical creates anotherLG Ch 8 p 6How do carbon radicals become stable again?1) they take atoms from stable molecules, forming new radicals2) two radicals come togetherWhich of these two is more likely?2 ways:a radicals are very reactive, very short lived, radical reactions are very fastso a radical is more likely to collide with a stable molecule than a radicalWhat are these kinds of reactions called?termination - two radicals come togetherBr Br+Branother propagation step+Br+The halogenation of alkanes is a radical reaction. What does its mechanism look like?CH4 + Cl2 CH3Cl + HClh!or heatInitiation step:Propagation steps:Termination steps:Cl ClCl Cl+hv orlightCH HH HCl+HCHHCl Cl+CH HH ClCl+Cl Cl+Cl ClHCHHCl+CH HH Cl+How are reactions involving radicals different from reactions of acids and bases or nucleophiles and electrophiles?electrons don't move in pairsHow are the arrows different?they are single-headed; they flow in opposite directionsWhich is more common in organic chemistry?only a few reactions in this course have a radical mechanismLG Ch 8 p 7What role do termination steps play?they are side reactions they slow the reaction downone recreates SM, one creates product, one creates a side productthey occur mostly at the end when no reagents are leftwe don't always worry about theseWhat role does the initiation step play?gets the reaction started - no light or heat, nothing happensWhy are many chemicals stored in dark bottles in cool places?to prevent radicals from formingWhat role do the propagation steps play?organic compound reacts and forms the product - main stepsDoes the reaction stop at the product shown? What other products would be formed?nope - the product could react with another Cl radicalCH2Cl, CHCl3,