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SC CHEM 334 - Forming acetals and imines

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Chem 334 1nd Edition Lecture 12Outline of Last Lecture I. Reducing alcoholsOutline of Current Lecture II. Alcohol’s to AcetalsIII. Addition of Nitrogen NucleophilesIV. Oxidation of AldehydesV. Carboxylic AcidCurrent LectureAlcohol Acetal O OH OH O O H H+ OH OH OTo go from an alcohol to an acetal, you first need to form a hemiacetal. Remember that these reactions cannot take place under basic conditions, and that these reactions are in equilibrium, meaning that they can go backwards or forwards. The addition of H2O drives equilibrium back to the starting aldehyde/ketone OO O H2O, H+ H HMechanism: H These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.O O H–O+–H O O+–H O+ OH O OH H H H H–O–H H O+ H H2O H–O–H O OH H – O OH O–H H2O O H H OH H OH H OH OH HAcetal reactivity:Aldehydes will react faster than ketones O O OH OH O O O H H+ Thioacetal:Thioactals are simply acetals derived from thiols (R-SH)O RS RS O HS HS S SThioacetals are useful for removal of carbonyl groups:S S H2, Raney Ni There are also several other ways to remove carbonyl groups besides using thioacetals, such as Clemmens or Wolff-Kishner ReductionsClemmenson reductionHO Zn(Hg) HCl, heatWolff-Kishner reductionO H2N-NH2 KOHAddition of Nitrogen Nucleophiles:A. Amines (NH3 and primary amines)  IminesO H2N-CH3,H+ NMechanism: H HO H O+ O–H O–H CH3–N+–H H–N+–CH3 H NH2–CH3 N+–CH3 N–CH3 H H H H2N-CH3 HH–O+–H H–N+–CH3 N–CH3Once again, the reaction is still in equilibrium, so we can go forwards or backwards.Imines amines: N–CH3 NaBH4 H–N–CH3 Or H2/NiReductive amination is taking a carbonyl group and reacting it all the way to an amineO N H–N NH2 H+ NaBH4 O 1. H+ H–N– NH2 H 2. NaBH4 HB. Amines (secondary amines)  enamines O N H+ N HThe term enamines means that there is a double bond next to amineMechanism: H O H O+ OH OH H– N+– H–N+– H H–N– N+– N– H H H–N– H–O+–H N+ N N– H N+–H C. hydrazine(H2N-NH2) or hydroxyamines (H2N-OH)hydrazones or oximesThese reactions have the same mechanism as primary amines from H2N-R, R=alkyl, aryl, -OH, and -NH2O H2NNH2, H+ N–NH2 O H2N-OH N–OH Oxidation of AldehydesOH [O] O [O] O H OHB. Ag2O, OH- Silver OxideO Ag2O, -OH O H OHSynthesis:O 1. BrMgCH3 H2SO4/Δ 2. H3O + Workup OHSynthesis: Br N NaCN NaBH4 SN2 N H O N DiBAHL -78⁰ H+ N H2OCarboxylic acid=CO2H=COOHNomenclature:When naming carboxylic acid structures, find the longest chain that contains the COOH. Drop e and add “-oic acid” as the suffix. OOH Pentanoic Acid OOH 2-methyl hexanoic acidFor a double bond, change “an” to “en”. Don’t forget about stereochemistry! O OH E-3-heptenoic


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