Week 10/Lecture Notes
Week 10/Lecture Notes CHEM 2321
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This 12 page Class Notes was uploaded by Hayley Lecker on Friday October 30, 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 292 views. For similar materials see Organic Chemistry I in Chemistry at University of Texas at El Paso.
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Date Created: 10/30/15
Organic Chemistry Week 10 Important Information Professor s Email isalutepedu Class Website organicutepeducourses2324 Class Code Ebook utep232Xfall2015 M5 Reductive Addition to Aldehydes 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 group and form an alcohol The carbonyl group is reduced E 5 13H by a nucleophilic addition of H ion ID H T 011 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 1 IlI 11mm E m CH IQCHEC C H3 C g g g g 2 Had I H E Pmt39i l 91 Key notes in the reaction is the H from LiAlH4 goes to carbonyl carbon Ang is a Lewis Acid so it is an electrophile so this leads to an increase in carbon s reactivity n as H I H a all I 53 fleo er A1 Li rr H E l lIIa Li a Hr RH l 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 3 quoteggquot I 4 AAICID L IiI C 1 Li 3 Hydrolysis is the last step to yield an alcohol l 6 H C DAJQ M II H rls DH 4 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 ii i ECH moltquot Alikhyck Esta They have different inductive effects III lac Em gt Inductive e e s 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 E b E RC QRquot quot1 3quot RCDE Eeanna nne E iact 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 DH ttlta alng alTa liI F Mada H ijlobutaml 1 HHEH JlEtlH LlIIg il a Elm CMWHECHEWCHQEHE Ei a l even milder reducing agent than sodium hDii39 hjidiE39idE is sodium cyanoborolrmjrdride NaGNEHal which will not reduce moat carbonyl ups Instead it re neea an iimine group fanning an amine A common use for ao lium cyanoibomlrmjr lt39ide is 13911 the reaction of an amine EL ketone to fonn El au batiituilte l amine IL CHM 1mm W Vquot Ha39AquotFJ H HalliJ N M lh E in rm 31 710 Solution in Elk o 1 mm H V IE I H lg r H 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 Mg Emmimam 39 CHEEHEEHEMEET Elm 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 e o e E Iiflg E n e e El l f Giig al reagent Reaction enviroment cannot contain acidic hydrogen atoms so no water aochos amines or carboxlyic acids can be used Hydrogen atoms pronates the Carbon bearing Mg so grignard reagent won t take place Solved Exemiae 32 Write a mechanism ior the reaction of ethyl niagneeinln innmine with methanoi Soiniion in the iolilowing mechanisma tile EBNIEEF ie not e ll39iown hecanee tile lGrignanfl reagent lhae signi cant ionic character tlhe E Mg r ie a counter ion The methoxide ion interaction with the 6Mg r is even more ionic r21 A an E egg9quotquot i5 i eII 3 n ang 1 engcng n gong The ailcohoil is a much stronger acid than the alkane and the lGrignanfl is a month stronger haee than the alhoxxi e ion Time ti39JE reaction proceeds to tllhe righta the aide of the weaker E39EidWJEEE pair a Girgnard reagent occurs with primary equot MEBI secondary or tertiary alkyl halides as well as we winyl and aryl halides Cl Br I work well as halogen while F doesn t because organofluorides are not very reactive l Et eaylmagaminmbmmidc I thjrlmngncsimntmomide Lithium reacts like Mg with halides to form organolithium Unlike grignard reagents organolthium does not need ether solvent but must use anhydrous reaction conditions L11 Clig ig HgEIiIg t 39339 rCIig g ltIgCIIzli m 1 Li z ral Li L l m Eh thjrliiifrhjum lt i H l J t i lithium 7 a l Li Z39asm gLi I F DEBS D g 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 a r 1 11 HEEHE co H4ng R C MEX F E E EH if II ll Hydrolysis of alkozide with dilute acid produces alcohol 11 l lg ghigm 31 2 mm 11120 L J lE r rlqiric1nhmanul H4955 G gn rd reagents madam primary sm arjr or tartar almh nla depem jmg an the gammy used F l39f ldl hjf HUIHDZ I pm lu es a primary a mh lm v31 ITIMEEHIIE E39Iilg i39IZI 3 11303 44 Dim hjrl l hmml 53 Ether al l hji d pmduBe m am39jr a llmhnls I M E l 39 gt AIJHUH 2 E a 1 EH 3 11305 55 And kaemnes pmdu e mummy a mhn lls 1 Mg a mr CH HggEIil g p C g g g g ID 11 IIlg g 1 331ch LIE T lm hjrl l pmtmul 04 Barbee dimtiiile 11315 e etmetut39e similar tel a E l I ijFll group In fact it is reallyr two ea rhetmjrl ape sharing one calhem atom i t Thus yen meet exclude atmeephetie ea rhetm liliexide from the teaelriieftm treeeel lming a Grigtma riil i39eaetiietm Hewe ve rj teacher with eathen iexi e ie a valuable technique fer the ejrtmtheeie ef Team helxjrllic a eiiiile mnteitming time were carbon than the erigitmel alkyl halide ll a r c 1quot HMEBI Stile aquot l quot L The mechanism ef the reatetien with 3133 is parallel to the meantime with a ea rhetmjrl grainy L22 The Wittig Reaction reference pages 341347 710 The Wittig Reaction In 1954 Georg Wittig discovered how to convert aldehydeketone to a carboncarbon double bond The Wittig reaction involves a nucleophilic addition of a phosphousstabilizied carbanion to ketone or aldehyde then elimination of phosophous gives an alkene Rt P111 e R M e fee P11 fill fix a Ecztca t JP x e P11 R R R eh Pile epheme li k A phosphous stablized carbanion ylide has a negative charged carbon and a positive charged phosphous adjacent to each other some ylides have sulfurs instead The net charge is zero The preparation of phosphous ylide has 2step reaction of triphenylphosphine and alkyl halide 1 A nucleophilic phosphous attacks the saturated carbon with halogen The halogenbearing carbon is usually a primary carbon The product is an alky triphenylphosphonium salt Eh P11 5 P11 P 3 REHng 1Ih P M r f P11 39tliphmylplmepime a plimaly alkyltm yphmmyl heephe imm ealt elker halide 2 The salt is treated with a strong base usually butyl lithium this removes a proton from carbon quotquot A aquot P11 11 il a CH13EH2 H3CHgquot Li 121 E 1111 Eh T11 ylide Ylide s are reasonace hybrids with 2 reasonace structures One has a charge of Phosphous and Carbon The other has a double bond between phosphous and carbon Pig a 111 1111 11 1quot it h Plij CHE Pl 131 When converting the carbonyl into alkene the ketone or aldehyde react with ylide in a typical nucleophlic addition reaction The reaction produces an intermediate called betaine II 11 F EP39E 15quotquot A y g is x 1 11 l PIrP ctm 39 LLE 13 i QC 39C li h Ill l A betaime Because of the close proximity of the postive charged Phosphouse and negatively charged Oxygen phosphous and oxygen form a bond and create a 4 memebered ring P11 quotquot1 VHFasi Jain1139 Ella u gc c IF Eh 1 H ill 1 i R I Hi l The ring rapidly collaspes to give alkene and triphenylphosphine oxide a very stable and usually insoluble compounds in this reaction 11 Pl 3 ilIa gal P115 I P1111Poz ESP i E I 1 P11 n P11 Hg39q E H R Ritz 1 11quot K Examples of Wittig reactions where cis and trans geometric isomers are found Pth E HCH 4 I o SHEi Ethjj idti soyolopootms sos 39339 til Pth IC H if I Hots Lay sHJJCH ssa sk L l t I 12Dipltlmylstltls s to Example of a solved wittig reactions lo ilill Cos sass quot if m T U th 2 11 This p oohiom has two possible solutions lbul tho following solution oursporos the glide from 1hoomolbutons at primary oilfile holids 0f the two possible solutions it gives o hotter yiolld Pilgp EHEHEEHEEHE L4 f H 2 L23 Carboxylic Acids Common and Systematic Nomenclasture reference pages 300301 71 THE FIRST PART OF THIS CHAPTER WAS COVERED A FEW WEEKS BACK Carboxylic acids COOH are present in or are derived from many natural substances A carboxylic acid is an oxygen doubled bonded to a carbon that is bonded to a hydrogen or alkyl group and also a hydroxy group OH To Name Carboxylic Acids similar to aldehyde 1 Name the parent compound 2 For straight chain alkanes drop the e of the alkane name and add the suffix oic acid to the parent name Example to the left gt if HglC HgC H CHECHEngcs oos Psotsooio acid 3 To number substituents assume that carbon bearing the carozylic acid functional group is 1 omit the number 1 but number the substitutents For eraample CHEJEGHEHEGDDH is 3methylhutan ie acid 4 When bonds in a ring do not drop the e before adding carboxylic acid to ring name E E ymlop ttantcaib xylic acid Some common carboxylic names are formic acid for methanoic acid acetic acid for ethanoic acid Carboxylic acids for a number of derivatives that are common chemical compounds these derivatives are formed by replacing the OH group with another heteroatomgroup Replacements include halohens ex Cl or Br this will form acyl halides Carboxylate RCOO these form carboxylic anhydrides Alkoxy RO these form esters and amino NR2 F forms amides Each has a specific naming system Acyl Halides For naming acyl halides add suffix oy to parent name follwed by sperate name for halogen o H E HgCHEE IC I Pmpanoyl chlmicle Carboxylic Anhydride For carboxlic anhydrides use proper carboxylic name then replace acid with anhydride 3 i E Hgii fCHE Etl ia oic Italially acetic Ester For esters first name the alkyl group bonded to oxygen follwed by carboxylic acid name using suffix oate to reaplace oic acid Name alkyl alkanotes if i A EC H HBIC HECHE E HgiC HEEZDE39HE a Methyl pmpmma te Ethyl cyclopmta ecmhoxylate Amides For amides replace final 0e of parent name with suffix amide Name secondary and tertiary amides as substituents to parent compounds by adding N to show group is bonded to nitrogen E39HEIE NHE39HE NmMethylethmml de Lt511311 N metlhyleeetmmi Nitriles Nitriles A carbonNitrogen TRIPLE bond are often considered deriviates of carboxylic acids because they are easily converted to acids and made from amides To Name A Nitrile 1 Determine parent name 2 Add suffix nitrile to parent name 3 Number substituents include carbon of nitrile in group when counting for positions 4 Use prefix cyano if nitrile group is a substituent HgCHQEHECEH M MEREGEN Elmm 39i lil 3 illlethylpeute tm e NE E C HQCU39H Cwmetlmmie acid Example 3 ei The eempeund ie an ester derived frem a tee Barbtin earhe yl ie acid Thule the IUPHG name fie phsemrl etheneete Lecture Notes Moodle Questions 1 For naming these the table acyl substitution was used It is hard to understand at first but once you get the hang it becomes very easy 3methylbutanoyl chloride methanol pyridine catalysis methyl 3methylbutanoate 3methylbutanoic anhydride water 3methylbutanoic acid ammonium 3methylbutanoate heat 3methylbutanamide 3methylbutanoic acid heat acid catalysis 3methylbutanoic anhydride 3methylbutanamide water acid catalysis heat 3methylbutanoic acid 3methylbutanoic acid methanol acid catalysis methyl 3methylbutanoate 3methylbutanoic acid ammonia heat 3methylbutanamide 3methylbutanoyl chloride sodium 3methylbutanoate 3methylbutanoic anhydride 3methylbutanoic anhydride methanol acid catalysis methyl 3methylbutanoate methyl 3methylbutanoate ammonia heat 3methylbutanamide 3methylbutanamide thionyl chloride heat 3methylbutanenitrile methyl 3methylbutanoate sodium hydroxide heat sodium 3methylbutanoate 3methylbutanoic acid diazomethane methyl 3methylbutanoate 3methylbutanoic acid thionyl chloride pyridine catalysis 3methylbutanoyl chloride 3methylbutanoyl chloride water 3methylbutanoic acid sodium 3methylbutanoate hydrochloric acid 3methylbutanoic acid 3methylbutanenitrile water acid catalysis heat 3methylbutanoic acid 3methylbutanoic acid ammonia ammonium 3methylbutanoate 3methylbutanoyl chloride excess ammonia 3methylbutanamide Pd hydrogenation reagent 1quot U va diieebugileluminum hydride qquot H LI vi rlil l E lithium tiiiitertbutmtyaluminum hydride qquot RLi H W alkyl lithium sf Ll M lithium dialkyleupirate sf Hi Dllll R H lR ClLll R Riliilgx Hr m gm 3 Grignard reagent 1quot H if Hl rditr lH lithium aluminum hydride f H
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