Week 9 Homework/Lecture Notes
Week 9 Homework/Lecture Notes CHEM 2321
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This 15 page Class Notes was uploaded by Hayley Lecker on Friday October 23, 2015. The Class Notes belongs to CHEM 2321 at University of Texas at El Paso taught by Dr. James Salvador in Fall 2015. Since its upload, it has received 59 views. For similar materials see Organic Chemistry I in Chemistry at University of Texas at El Paso.
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Date Created: 10/23/15
Organic Chemistry Week 9 Important Information Professor s Email isalutepedu Class Website organicutepeducourses2324 Class Code Ebook utep232Xfall2015 L20 M3M4 76 reference pages 319324 76 Reaction with Nitrogen Nucleophiles When aldehydes and ketones reaction with primary amines a class of compounds with a carbonnitrogen double bond is produced called imines sometimes called Schiff bases 1W3 CH2JCITH BEENHg Iii ECH N Meth rl I Ipiqaa imine Biliii Imines lack stablity but are important intermediates in many reactions Formation of lmine 1 Nucleophilic addition to carbonyl group 2 A proton transfer to oxygen The solution requires acid catalysis in solution where a pH is between 3 and 5 Outside this range the reaction slows down PF EH EiH it on II I H CHEEHgClII Cir132m CH3NH2 CHng H ILliCliIg EH CHECHEEIEH H trim At a high pH the 3rel step is the rate limiting step in the reaction sequence a C g g llI miquot g g 39539 g H H ill The elimination step proceeds slowly because of the charge separtion in the products and the number of charged species changes from substrate to products The substrate is uncharged and the products both have a charge When the number of charged species increases from reactants to products the reaction requires more energy than if there is no change in number of charged species When pH is 3 to 5 the solution contains enough protons to pronate OH group The OH group then leaves as water This requires less energy than outside the pH range This is less energy because there is no change in number of charged species H g z m In ifampiI E 1 I li IC Hill C x H 1 E1212 MC x When the solution has a low pH pronation occurs at amine itself In this case amine is not a nucleophile because nitrogen no longer contains a nonbonding pair of electron Without the pair of electron bonding to carbonyl group this reaction doesnot take place a F39 v a quotJ lf H2 l39 4 i NH3 Secondary amines R2NH react as nucleophiles with ketones and aldehydes and form enamines When they dehydrate they make a stable compound with a carboncarbon double bond f rm N J l E j i I l Hg my e t39I Pila di r a N mjnhem mipe dtm Wg 39 The reaction starts with a nucleophile reacting with carbonyl group to form intermediat carbinoamine Next carbinoamine dehydrates water loss Because nitrogen has no hydrogens adjacent carbon losses hydrogen Loss of hydrogen results in double bond between CC Enamines are useful intermediate reactions Nucleophile I Product NHEIDH I c NoH Hydruxyrlamiine Am mime HEINNHE Hydm ne A lilydrawing E II Huic of Phenyl lwdmimei A phe njrl lllyrdraznne Nucleophile I Product 5 GEN 39 ND H a I 1quot N02 a nmimitmph n mwdr m E ii 2 4 ilnil prh flhfdi 39 l I I r Semicam llhaaide A seminarlmmme L21 Reductive Addition to Aldehvdes and Ketones 7778 reference pages 326338 77 Reaction with Hydride Nucleophile Reductive reactions is a term used by chemists when talking about addition reactions In reduction reactions two hydrogens bonded to a carbon and oxygen in a conbonyl R IJHE group and form an alcohol The carbonyl group is reduced v by a nucleophilic addition of H ion H I 0H or Alcohol A complex metal hydrid delievers the H ion to carbonyl carbon Examples of metals used are LiAlH4 lithium aluminium hydrid and NaBH4 sodium borohydride LiAlH4 is very reactive and a very powerful reagent When using the reaction is carried out in a solution of anhydrous terahydrofruan or diethyl ether It cannot be carried out in water because a violent reaction will occur and it gives off hydrogen gas The hyndrogen gas then iginites because of the high heat of reaction The desiered reaction is below 3 I I 1 MM E EI I CH IgCHgC C H3 CHg 39HgCHg Hg a aw I H 3 Pme 91 Key notes in the reaction is the H from LiAlH4 goes to carbonyl carbon AIH3 is a Lewis Acid so it is an electrophile so this leads to an increase in carbon s reactivity A H J I H E 3 Jr IKE ersz AIR L l h Ell 13 L11 Vr H H The reaction occurs 4 times for each H ion 1 mole of LiAlH4 can react to 4 moles of a ketone or aldehyde H H a all m 1 xiii M Li F H E o AJ Li Hf EH I Hydrolysis is the last step to yield an alcohol 11169 H c pfm Li II E DH I LiAlH4 can reduce a variety of functional groups NaBH4 is less reactive more selective and reduced usually only aldehydes and ketones It is carrried out in aqueous alcohol So why is sodium borohydride selective Look at an ester carbozlyic acid derviative vs an aldehyde i quotiquot REEI REDEquot Aldehyde Ester They have different inductive effects EEEIE 339 Inductive e 39 cts The higher positive charge should make the carbonyl carbon of the ester more suseptible to nucleophilic addition but expierments show it is less and less reactive Ester have resonance so with inductive effects the carbonyl carbon ends have less partial positive charge than the aldehyde our Ir r nozos eII Eosousuoo o bot Sodium borohydride is easier to handle in the lab and can be run in water with ethanol added to dissolve substrate Since it reacts with acid base is added to make sure it only reacts with substrate 1 H i l i Hfg maUH DH H Ejrulohutaml i oven milldo r usdluoiug ogouit i iau sodium hoi39ohjrdiids is sodium oji39ouoihorohjrdrido NoGNEHslj which Willi not reduce most oai39houjrl ups Iusiisad it moduloes on imius group forming an amino A summon use for sodium wouoihoiuhjrdliide is iu the messtint of 3111 amino with s hstoue to form s substituted amine Hall U IL CHM hummus 14H i NM h E II iir39Hii39 miss 710 Solution no 78 Carbon Nucleophiles Organometallic compounds contain polar colvalent bonds between a carbon atom and a metal atom Metals are less electronegative than carbon so carbon bond is the negative end of the dipole Gridnard reagent significant organo reagent developed in 1902 by Victor Gridnard he received the Noble Prize in 1912 Grignard Reagent is an organomagnesium halide RMg X product of reaction of magnesium metal and alkyl halide cagrcn nln ge rcngnigc gnger nae Diethyl ether most cmmon solvent for for a grignard reagent because ether donates a pair of electrons to Mg Grignard reagent is complex Mg must readily react with alkyl halide without ether Grignard reagent do not readily form R Q E I n iIg n n o n ne Grignard reagent Reaction enviroment cannot contain acidic hydrogen atoms so no water alochols amines or carboxlyic acids can be used Hydrogen atoms pronates the Carbon bearing Mg so grignard reagent won t take place Solved Exemiae 32 a mechanism ior the reaction of ethyl lll l39lEinEEiIJ i hromide with methanoil Sciatica In the ioliowing mechanisma the EBMEEir ie not chian hecanee the lGrignai reagent hae signi cant ionic character the IE39lli39g 39si ie conei ered a counter ion The methoxide ion interaction with the Mg r is even Inoie ionic 3 25 112 I r IL ii lI 3 n ncng 1 CH3EI Io H non The aicohoil is a much stronger acid than the alha ne and the lliirignai reagent in a mnch Stronger hase than the alhoni e ion Thus the reaction proceeds to the righta the aide of the weaher acid haee pair D Girgnard reagent occurs with primary quot BI M39 H a j gm secondary or tertIary alkyl halides as well as we mm mm wmyl and aryl halides Cl Br I work well as WWWmm halogen while F doesn t because Mg organofluorides are not very reactive f w r p ghag r tetrahjrtilm nan l Bmcaylmagmeoinmbmmide I E a 39 lm x quot Phoajdmagncsimn Lithium reacts like Mg with halides to form organolithium Unlike grignard reagents organolthium does not need ether solvent but must use anhydrous reaction conditions A A Li CHEEI IECHQCHEET iI CHEEHQEHECHEH Imam Ht iitnll CHI Li j 2 Li L J w E Ethyl 39 Erquot Pittmrlii tm A arquot hurtr lt i a lt1 lithium iii 7 111 Li C am Li I 1 F ethyl ether D a SSH Grignard reagent and organolithium are strong nucleophiles strong bases In a nucleophilic addition reaction carbon nucleophile of organometallic compound reacts with carbon electrophile of carbonyl group to produce alkoxide it gt i r a HEEHE quota K H CI J 11 ng R C t MEX E E GH If II III Hydrolysis of alkozide with dilute acid produces alcohol HI 2 HEEL H Cquot l Eq ohmanul 94 g rd reagents pmdum primary Remindaw or tertiary a39lmhola dopam img on the 39l39h flillfl 112 1153i F f l y e HDlHDI I pm luoes a primary allmh lm v31 llhtlgl h rs EHEEIH 3 11303 43 Di 1 gd l hmaml 153 Either a39l lehjides pmduoe EEIl Illd E39jf alllmhn39ls I M h 1 I we rlg o 2 ammo A EH3 3 H303 55 And ketones pmduoe mummy Hamilnulls I Mglr mr EH HgEIIg l g Ir D 31 39E gm 2 I 3 H3013 33 11112 T m fhjgrl l pmtanol 4551 U l h dieeiiiie haze a structure similar to e ee39rhehjrii gmuu In fact it is really 39l39h fliiijfl 31upe eheri39hg ene calhem ateru i t Thuej yen ru uet exeiiude etmeephetie ea rheh iiiieeijde frem the maetieu Lev lming a Grigheriil maetieu Heweverj reactien with eathen die de a valuable technique fur the ejrhtheeie ef hammer aeiiiie eentei39hing nine were eerben than the erigihe39l aiiikjrii haiii em wee H309 r acid 343 The meehauiem ef the reeetien with CUE is peraiiiie39l tn the tealetie h With a ea39rhehjrl green Lecture NotesMoodle Answers Carbonyl with secondary amine yields As you can see in the image above water is removed and the double bond changes to in between the carbons and the nitrogen is added to it making it a tertiary nitrogen D f Oxonlum Imine Hydrazine Aldehyde keto form Enamine Eno ether Hydroxylamine Primary amine Enolate Acetal Enol Hydrate Tertiary amine Hemithioketal Hemiaminalgemina amino alcohol carbinol amine this is a geminal amino alcohol Hemiketal Thioacetal Hydrate Oxonium Enol ether Hemiacetal Enolate Ketal Iminium Oxime Quaternary ammonium Ammonia Thio ketal Ketone keto form Hemithioacetal Secondary amine iminium hydrazone tertiary amide car Kn carboxylate carboxyl D primary amide G H anh dride KnI y WE acid or acy halide rm secondary amide CL ester 0 nitrile R EEN iiii R BE cyanohydrin Wm carboxylic acid acy Inetnfyl pmpanuate EMWIpmpanenit le Whylpmpanam e EMHyIpmpanuiE arid 5mm Emwlpmpanuate EMWIpmpanuiE anhydr e 2mnylpmpanuyl Ehl l i E thiunyl II lll l i E umytluhexymammmnm
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