CH 243 Organic Chemistry Lecture Notes for April 22, 2003

How is your laboratory research project going?  Please write up an one-page proposal of what you plan to do!
To get ready for exam # 1, prepare a one-page (8 x 11, front and back) fact sheet to be used during the exam.

Finish Chapter 17

I.  Nucleophilic addition to alpha-beta-unsaturated aldehydes and ketones
    A.  Direct addition (added to the carbonyl group) favored when a strong nucleophile (base) is used and the reaction is irreversible.
    B.  Conjugated addition (addition across the conjugated system) favored when a weak nucleophiles (bases) are used.

II.  Nucleophilic Addition to alpha-beta-unsaturated carboxylic acid derivatives.
    A.  Conjugated addition with weak nucleophiles (bases)
    B.  Strong nucleophiles for nucleophilic acyl substitution products.

Chapter 18 More About Oxidation-Reduction Reactions

I.  Oxidation States of Carbon

II.  Reduction Reactions
    A.  Reduction by two hydrogen atoms (catalytic hydrogenations).
        1.  Alkenes, alkynes, imines, and nitriles are reduced by H2 and Pt, Pd, or Ni
        2.  Alkynes to cis-alkenes with a H2 and a Lindlar's catalyst
        3.  Carbonyl group of aldehydes and ketones with H2 and Rainey Ni
        4.  Acyl chloride reduced to alcohol, stopped at aldehyde with partially deactivated Pd.
        5.  Carboxylic acids, esters, and amides not reduced by catalytic hydrogenation.
        6.  Increasing reactivity toward H2, Pd/C:  imine < nitrile < ketone < alkene < aldehyde < alkyne < acyl chloride
    B.  Reduction by addition of an electron, a proton, an electron, a proton
        1.  Dissolving metal reduction:  Alkyne is reduced to a trans alkene by sodium in liquid ammonia.  Sodium donates an electron and ammonia donates a proton.
    C.  Reduction by a hydride ion and a proton
        1.  Aldehydes and ketones are reduced by NaBH4 and LiAlH4
        2.  Carboxylic acids, esters, and amides are reduced by LiAlH4
            a.  amides are reduced to amines
        3.  Sterically bulky hydrides reduce esters and acyl chlorides to aldehydes.
        4.  Alkenes and Alkynes are not reduced by hydride ions.
        5.  increasing reactivity toward H-, hydride ion:  nitrile < amide < caboxylic acid < ester < imine < ketone < aldehyde < acyl chloride

III.  Oxidation of Alcohols
    A.  H2CrO4 (CrO3 or Na2Cr2O7 in aqueous acid) most commonly used to oxidize 1o alcohol to carboxylic acid and 2o alcohol to ketone.
    B.  Pyridinium chlorochromate (PCC) is used to oxidize a 1o alcohol to an aldehyde.
    C.  Swern oxidation:  no toxic chromium, dimethyl sulfoxide, stops at aldehyde
    D.  3o alcohols not oxidized

IV.  Oxidation of Aldehydes and Ketones
    A.  Aldehydes are easily oxidized to carboxylic acids using any reagent that oxidizes a 1o alcohol to a carboxylic acid..
        1.  Tollen's Reagent:  Ag2O, NH3, mild reagent oxidizes aldehyde to carboxylic acid, but not 1o alcohol. Silver mirror test.
        2.  Baeyer-Villiger oxidation:  peroxyacid, oxidizes an aldehyde to a carboxylic acid and a ketone to an ester.

V.  Oxidation of Alkenes with Peroxyacids.
    A.  An epoxide is formed.
        1.  concerted reaction
        2.  more substituted alkenes react faster
        3.  stereospecific

VI.  Hydroxylation of Alkenes
    A.  Alkenes are oxidizes to 1,2-diols (vicinal diols) by KMnO4 or OsO4

VII.  Oxidative Cleavage of 1,2-diols with HIO4.

VIII.  Oxidative Cleavage of Alkenes.
    A.  Use O3 and a "work-up"
    B.  KMnO4 with acid or base and heat

IX.  Oxidative Cleavage of Alkynes use O3 no work-up needed

X.  Designing a Synthesis V:  Functional Group Interconversion

Chapter 19 Carbonyl Compounds III, Reactions at the alpha-carbon

I.  Acidity of the alpha-carbon p. 828

II.  Keto-Enol Tautomerism

III.  Reactivity Consideration