chapter 10 organometallic compounds

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Chapter 10 Organometallic compounds. 10.1 Introduction 10.2 Preparation of organolithium and organomagnesium compounds 10.3 Carbanions as Br sted bases 10.4 Applications of organometallic comp. in organic synthesis - PowerPoint PPT Presentation

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  • What' s Organometallic Compounds?A carbon-metal bondSodium acetylideSodium ethoxideThe natures of CM bondsThe electronegativity of the metalCarbanions()

  • 10.2 Preparation of Organolithium and Organomagnesium compounds Alkyl halideTetrahydrofuranTHF()Anhydrous!Butyl bromideButyllithium(80% -90%)Diethyl etherEt2O

  • Grignard reagents: Alkylmagnesium HalidesPhenyl bromideCharacteristics of the reactions:Alkyl groups: 1, 2 , 3 alkyl, cycloalkyl alkenyl, aryl2. Reactivity:4. Exothermic3. Without substitutes:V. Grignard andP. Sabatier1912 Nobel PrizeAlkyl > Alkenyl or ArylRI > RBr > RCl > RFPhenylmagnesiumBromide (95%)P223,7.4Ch.P185(3)

  • Grignard found that, in the presenceof ether, magnesium reacts with alkyl and aryl halides at room temperature to form organo-magnesium compounds. These solutions,called "Grignard reagents" react with most functional groups in a synthetically useful way. For this discovery, tremendously useful in laboratory and industrial synthesis, he was awarded the 1912 Nobel Prize in Chemistry(shared with Paul Sabatier,discoverer of catalytichydrogenation).Franois Auguste Victor Grignard 1871-1935http://www.nobel.se/chemistry/laureates/1912/grignard-bio.html

  • Acidity of hydrocarbon:The stronger the acid is, the weaker the conjugate base is.10.3 Carbanions as Brsted bases:

  • Basicity of anions:Carey(4th):547

  • Organolithium compounds and Grignard reagents as base:RM reacts with much weaker acid than H2OCh. P186

  • 10.4.1 Synthesis of alcohols using Grignard reagentsReactions with carbonyl compounds:Grignard reagents react with Formaldehyde( ) Primary alcohols:B. Grignard reagents react with higher aldehydes secondary alcohols:P296,9.10

  • Example:Synthesis of Acetylenic alcohols ():C. Grignard reagents react with ketones Tertiary alcohols:

  • 10.4.2 Retrosynthetic analysis ()Target MoleculePrecursorsn-BuMgX + CH3COCH3n-BuBr + Mg

  • Elias James Corey1928- which changed the way organic chemists undertake the synthesis of complex natural products, the synthesis of longifolene, maytansine, the ginkolides, prostaglandins and leukotrienes, the development of new synthetic methods, particularly using chiral catalysts, and the application of computers to synthesis design are among his most notable achievements.Corey has received many honors, including the Wolf Prize (1986), the National Medal of Science (1988), the Japan Prize in Medicinal Science (1989) and the Nobel Prize in Chemistry (1990).Born in Massachusetts, Corey obtained the Ph.D. at M.I.T. (1951), was on the faculty at the University of Illinois (1951-59) where he became full professor at the early age of 27, and since 1959 he has been professor at Harvard. Hisresearch associates (graduate students and postdoctoral fellows) number over 500 and populate the academic and industrial laboratories of Europe, Asia and the Americas.Professor Corey (to collea-Gues and friends, E.J.) is known for his many spectacular contributions to synthetic organic chemistry. The concept of "retrosynthetic analysis",

  • Preparation of lithium dialkylcuprate reagents:Coupling reactions of Organocoppers with AlkylhalidesCh.P185(3)10.4.3 Alkanes synthesis by using organocopper reagents

  • Characteristics of the reaction:SN2 reaction The order of the reactivity : CH3 > 1> 2> 3 I > Br > Cl > F2. To alkyl halides, R: primary,vinyl and aryl groups. To Lithium dialkylcuprate, R: primary group or -CH3.

  • 12.44 Ziegle-Natta Catalysis of Alkene PolymerizationZiegle catalyst: TiCl4-Et2AlClEthylene Ethylene oligomersCharacteristics of the products:Ethylene oligomers with 6-18 carbonsHigh-density G. Nattas contributions:Isotactic polypropylene () Carey:P56714.15

  • Coordination polymerizationPolypropylene industry was started K. Ziegle and G. Natta shared the 1963 Nobel Prize in Chemistry

  • Problems: Carey(4th)P573 14.15 (b), (d)14.17 (h), (m), (n)14.18 (d), (e)14.19 ((b), (f)14.20 (d), (e)14.21 (a)-(c)14.22 (b), (f), (g)14.2314.2514.26*14.2714.28 (b)14.29

    Largely, essentially, lie between these extremes. An carbanion is an anion which the negative charge is borne by carbon.Organoithium and organomagnesium compounds are of great importance in organic synthesis. These reactions are usually carried out in ether solvents. Commonly. Grignard reagents are stable in ether solvents. Just at somewhat slowly rates. Alkyl iodides are the most reactive, alkyl fluorides are seldom used. Any substrate that bears a hydroxyl, a carbonyl or a cyano groups.Organolithium compounds are prepared in cool bath. Organolithium and organomagnesium compounds are very stronger base. they react with proton donors even as weakly acidic as water and alcohols. They also abstract protons that are much less acidic than those of water and alcohols.A carbonyl group is quite polar. Grignard reagent attacks carbonyl to lead to an alkoxylmagnesium halide, Here, a new CC bond is formed. after acidic hydration to form primary alcohols. In the same way as formaldehyde.Benzyl alcohol. Organolithium compounds react with carbonyl compounds in the same way that Grignard reagent do.In planning synthesis we are required to think backward, to work our way backwards from relatively complex molecules to simpler ones that will act as the precursor. This process is called retrosynthetic analysis.Copper(I)halide reacts with two equivalents of an alkyllithium in diethyl ether or THF. Primary alkyl iodides are the best substrates. Elimination becomes problem with secondary or tertiary alkyl halides. SN2 reaction. ROTs is more reactive.

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