Organic Chemistry 2 · Carbonyl and enolate chemistry
Addition to aldehydes and ketones: practice problems
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- Acetone cyanohydrin from acetone and HCN
- Track addition in an aqueous carbonyl system
- Follow a carbon nucleophile
- A fluorinated aldehyde in acidic water
- A geminal diol returns to a carbonyl
- Alcohol addition with a basic catalyst
- A hemiacetal under basic equilibrium conditions
- An internal alcohol encounters a ketone
- Recovering a carbonyl from a cyanohydrin
Draw the mechanism 89
- Track addition in an aqueous carbonyl systemDraw nucleophilic addition and catalyst-regenerating proton transfer with all atoms conserved.
- Follow a carbon nucleophileTrack carbon-end cyanide addition and protonation without moving the nitrile pi bonds.
- A fluorinated aldehyde in acidic waterComplete acid-catalyzed hydration using a neutral nucleophile and regenerate the catalyst.
- A geminal diol returns to a carbonylReverse hydration without expelling hydroxide from an acid-activated substrate.
- Alcohol addition with a basic catalystConnect alcohol activation, carbonyl addition and catalyst-regenerating protonation.
- A hemiacetal under basic equilibrium conditionsTrace carbonyl recovery and distinguish cleavage at the acetal carbon from methyl substitution.
- An internal alcohol encounters a ketoneCount a five-membered hemiketal ring and retain both oxygen identities.
- Recovering a carbonyl from a cyanohydrinBreak the newly formed C–C bond while preserving the nitrile triple bond.
- A sulfur donor adds to an aldehydeTrack sulfur-end addition, a solvent proton shuttle and expanded-valence sulfur bookkeeping.
- NaBH₄ reduction — benzaldehyde to benzyl alcoholDraw hydride transfer from a B–H bond, then add a proton to oxygen.
- Cannizzaro reaction — benzaldehyde disproportionationFollow hydroxide addition, concerted intermolecular hydride transfer and final proton transfer.
- Sulfur capture without dehydrationDistinguish hemithioacetal addition from thioacetal condensation and regenerate a sulfur nucleophile.
- Wittig reaction — butanal to pent-1-eneFollow both alkene carbons and the oxygen as the four-membered Wittig ring forms and breaks.
- Wittig methylenation of acetoneDraw the deprotonation of methyltriphenylphosphonium by butyllithium, the addition of the ylide to acetone, ring closure to the oxaphosphetane and its collapse to 2-methylpropene and triphenylphosphine oxide.
- Wittig ethylidenation of cyclohexanoneDraw the formation of the ethylidene ylide with butyllithium and its Wittig reaction with cyclohexanone, ending with ethylidenecyclohexane and triphenylphosphine oxide.
- Wolff–Kishner reduction of cyclohexanoneDraw the formation of cyclohexanone hydrazone and its base-promoted reduction, with loss of nitrogen gas, to cyclohexane.
- Oxygen-18 exchange of acetone through its hydrateDraw acid-catalysed addition of labelled water to acetone, proton transfers in the gem-diol and loss of unlabelled water that give oxygen-18 labelled acetone.
- Sodium acetylide adds to acetone: 2-methylbut-3-yn-2-olDraw the acetylide carbon adding to the carbonyl carbon of acetone and the NH4+ workup that protonates the alkoxide to 2-methylbut-3-yn-2-ol.
- 1-Phenylbut-3-en-1-ol from allylmagnesium bromideDraw allylmagnesium bromide adding to benzaldehyde and the NH4Cl workup that gives the homoallylic alcohol 1-phenylbut-3-en-1-ol.
- 1-Allylcyclohex-2-en-1-ol by Grignard 1,2-additionDraw allylmagnesium bromide adding 1,2 to cyclohex-2-enone and the NH4Cl workup, and explain why the Grignard reagent attacks the carbonyl carbon rather than the β-carbon.
- Cyanide-catalysed benzoin: 4-methoxybenzaldehyde to anisoinDraw the cyanide-catalysed benzoin condensation of 4-methoxybenzaldehyde, showing how the cyanohydrin anion reverses the polarity of the aldehyde carbon.
- Base-catalysed hydration of acetaldehyde to ethane-1,1-diolDraw hydroxide adding to the carbonyl carbon of acetaldehyde, then proton transfer from water to the alkoxide that regenerates hydroxide.
- 1-Phenylpropan-2-ol from acetaldehyde and a benzyl GrignardDraw benzylmagnesium chloride adding to the carbonyl carbon of acetaldehyde and the ammonium chloride workup that gives 1-phenylpropan-2-ol.
- Regenerating heptanal from its bisulfite adduct with Na2CO3Draw carbonate removing the hydroxyl proton of sodium 1-hydroxyheptane-1-sulfonate and the alkoxide pushing out sulfite to give heptanal.
- Bisulfite adduct of heptanal: 1-hydroxyheptane-1-sulfonateDraw the sulfur of bisulfite adding to the carbonyl carbon of heptanal and the water-relayed proton transfer that gives sodium 1-hydroxyheptane-1-sulfonate.
- 1,1-Diphenylpentan-1-ol from butyllithium and benzophenoneDraw n-butyllithium adding to benzophenone and the NH4Cl workup that gives the tertiary alcohol 1,1-diphenylpentan-1-ol.
- Cannizzaro reaction of 2,2-dimethylpropanalDraw hydroxide addition, hydride transfer and the final proton transfer that split two 2,2-dimethylpropanal molecules into the alcohol and the carboxylate.
- Hydration of chloral to chloral hydrateDraw water adding to the carbonyl carbon of chloral and the two proton transfers that give the isolable chloral hydrate.
- Corey–Chaykovsky reaction: cyclohexanone to 1-oxaspiro[2.5]octaneDraw NaH deprotonating trimethylsulfonium, the ylide adding to cyclohexanone, and the alkoxide displacing dimethyl sulfide to close the spiro epoxide.
- Crossed Cannizzaro: benzaldehyde to benzyl alcoholDraw hydroxide adding to formaldehyde, hydride transfer from that adduct to benzaldehyde, and the proton transfer that gives benzyl alcohol and formate.
- Acetone cyanohydrin from acetone and HCNDraw cyanide adding to the carbonyl carbon of acetone and HCN protonating the alkoxide to give acetone cyanohydrin.
- Mandelonitrile from benzaldehydeDraw cyanide addition to benzaldehyde and protonation of the alkoxide on acidification, and explain why mandelonitrile forms racemic.
- 2-Hydroxy-2-methylbutanenitrile from butan-2-one and KCNDraw hydronium protonating the carbonyl oxygen of butan-2-one and cyanide adding to the activated carbonyl carbon to give 2-hydroxy-2-methylbutanenitrile.
- 2-Hydroxy-2-methylpropanoic acid from acetone cyanohydrinDraw acid-catalysed hydrolysis of the nitrile of acetone cyanohydrin through the amide to 2-hydroxy-2-methylpropanoic acid and ammonium.
- 1-Amino-2-methylpropan-2-ol from acetone cyanohydrinDraw two hydride transfers from LiAlH4 to the nitrile carbon of acetone cyanohydrin and the aqueous workup that frees the primary amine.
- Cyclopropane-1,1-diol from cyclopropanone and waterDraw water adding to the strained carbonyl carbon of cyclopropanone and the proton transfers that give cyclopropane-1,1-diol.
- 1-Phenylprop-2-yn-1-ol from ethynylmagnesium bromideDraw ethynylmagnesium bromide adding to benzaldehyde and the NH4Cl workup that gives the propargylic alcohol 1-phenylprop-2-yn-1-ol.
- (2S,3R)-3-Phenylbutan-2-ol by Felkin–Anh LiAlH4 reductionDraw LiAlH4 adding hydride to (R)-3-phenylbutan-2-one and the water workup, and use the Felkin–Anh model to explain why (2S,3R)-3-phenylbutan-2-ol is the major diastereomer.
- (2R,3R)-3-Phenylbutan-2-ol by Felkin–Anh Grignard additionDraw methylmagnesium bromide adding to (R)-2-phenylpropanal and the NH4Cl workup, and use the Felkin–Anh model to explain why (2R,3R)-3-phenylbutan-2-ol is the major diastereomer.
- 1-Phenylethanol from benzaldehyde and methylmagnesium bromideDraw methylmagnesium bromide adding to the carbonyl carbon of benzaldehyde and the NH4Cl workup that gives 1-phenylethanol.
- Isopropylmagnesium bromide reduces di-tert-butyl ketoneDraw the six-membered cyclic transfer of a β-hydrogen from isopropylmagnesium bromide to the carbonyl carbon (releasing propene) and the workup to 2,2,4,4-tetramethylpentan-3-ol.
- 1-Phenylcyclohexan-1-ol from cyclohexanone and phenylmagnesium bromideDraw phenylmagnesium bromide adding to cyclohexanone and the NH4Cl workup that gives the tertiary alcohol 1-phenylcyclohexan-1-ol.
- Acid-catalysed ring closure: 4-hydroxybutanal to tetrahydrofuran-2-olDraw protonation of the aldehyde oxygen, attack of the chain OH on the carbonyl carbon, and loss of the proton to give tetrahydrofuran-2-ol.
- Horner–Wadsworth–Emmons: benzaldehyde to ethyl (E)-cinnamateDraw NaH deprotonating triethyl phosphonoacetate, the carbanion adding to benzaldehyde, ring closure onto phosphorus and fragmentation to ethyl (E)-cinnamate and diethyl phosphate.
- HWE reaction of cyclohexanone: ethyl cyclohexylideneacetateDraw NaH deprotonating triethyl phosphonoacetate, its carbanion adding to cyclohexanone, ring closure onto phosphorus and fragmentation to ethyl 2-cyclohexylideneacetate.
- HWE: 2-methylpropanal to ethyl (E)-4-methylpent-2-enoateDraw the phosphonate carbanion from triethyl phosphonoacetate adding to 2-methylpropanal, oxaphosphetane formation and collapse to ethyl (E)-4-methylpent-2-enoate.
- Hydration of formaldehyde to methanediolDraw neutral water adding to formaldehyde, then the two water-relayed proton transfers that give methanediol.
- Selective NaBH4 reduction: 4-oxopentanal to 5-hydroxypentan-2-oneDraw the hydride of borohydride adding to the aldehyde carbon of 4-oxopentanal (not the ketone) and the protonation of the alkoxide by ethanol.
- Intramolecular Cannizzaro reaction: glyoxal to glycolateDraw hydroxide addition to glyoxal, the 1,2-hydride shift between its two carbonyl carbons and the proton transfers that give glycolate.
- Julia–Kocienski: benzaldehyde to (E)-pent-1-enylbenzeneDraw KHMDS deprotonating the PT sulfone, addition to benzaldehyde, the Smiles rearrangement and the elimination of SO2 and tetrazolate to (E)-pent-1-enylbenzene.
- cis-2-Methylcyclohexanol from L-Selectride reductionDraw L-Selectride delivering hydride to the equatorial face of 2-methylcyclohexanone and the peroxide workup, and explain why cis-2-methylcyclohexanol is the major diastereomer.
- cis-4-tert-Butylcyclohexanol by L-Selectride reductionDraw equatorial hydride delivery from L-Selectride to 4-tert-butylcyclohexanone and the peroxide workup, and explain why the bulky reagent gives cis-4-tert-butylcyclohexanol with an axial OH.
- 1-(Phenylethynyl)cyclohex-2-en-1-ol from an alkynyllithiumDraw lithium phenylacetylide adding 1,2 to the carbonyl of cyclohex-2-enone and the NH4Cl workup, and explain why direct addition beats conjugate addition.
- (E)-4-Phenylbut-3-en-2-ol by Luche reductionDraw 1,2-hydride delivery to the carbonyl carbon of (E)-benzalacetone under Luche conditions and protonation by methanol, keeping the E alkene.
- Cyclohex-2-en-1-ol by Luche reductionDraw 1,2-hydride delivery to the carbonyl carbon of cyclohex-2-enone under Luche conditions and protonation by methanol.
- Methyllithium adds to di-tert-butyl ketoneDraw the C–Li bond pair of methyllithium adding to 2,2,4,4-tetramethylpentan-3-one to give a lithium alkoxide, and water protonating it to 2,2,3,4,4-pentamethylpentan-3-ol.
- (E)-Pent-3-en-2-ol from MeMgBr and crotonaldehydeDraw methylmagnesium bromide adding 1,2 to (E)-crotonaldehyde and the NH4Cl workup that gives (E)-pent-3-en-2-ol, keeping the alkene geometry.
- MPV reduction: acetophenone to 1-phenylethanolDraw the Meerwein–Ponndorf–Verley reduction of acetophenone: coordination to aluminium, hydride transfer from isopropoxide, and alkoxide exchange with 2-propanol.
- MPV reduction: cinnamaldehyde to cinnamyl alcoholDraw the Meerwein–Ponndorf–Verley reduction of cinnamaldehyde and show why the hydride reaches only the aluminium-bound carbonyl carbon, leaving the C=C untouched.
- 1-Deuterio-1-phenylethanol from acetophenone and NaBD4Draw NaBD4 adding deuteride to acetophenone and methanol protonating the alkoxide to 1-deuterio-1-phenylethanol, and explain why the product is racemic.
- α-Deuteriobenzyl alcohol from benzaldehyde and NaBD4Draw NaBD4 delivering deuteride to benzaldehyde and methanol protonating the alkoxide, and use the label to show which atom comes from boron and which from the solvent.
- trans-2-Methylcyclohexanol from NaBH4 reductionDraw axial hydride attack by NaBH4 on 2-methylcyclohexanone and protonation by methanol, and explain why trans-2-methylcyclohexanol is the major diastereomer.
- 4-(1-Hydroxyethyl)benzonitrile by selective NaBH4 reductionDraw NaBH4 reducing only the ketone of 4-acetylbenzonitrile and methanol protonating the alkoxide, and explain why the nitrile survives.
- trans-4-tert-Butylcyclohexanol by axial hydride attackDraw axial hydride attack on 4-tert-butylcyclohexanone and protonation by methanol, and explain why the trans alcohol with an equatorial OH is the major diastereomer.
- 9-Fluorenol from 9-fluorenone with NaBH4Draw NaBH4 adding hydride to the ketone carbon of 9-fluorenone and methanol protonating the alkoxide to give 9H-fluoren-9-ol.
- Racemic 1-phenylethanol from acetophenoneDraw hydride addition to acetophenone and protonation by ethanol, and explain why 1-phenylethanol forms as a racemic mixture.
- Racemic butan-2-ol from butan-2-one and NaBH4Draw NaBH4 reducing butan-2-one and ethanol protonating the alkoxide, and explain why the butan-2-ol formed is racemic.
- Cinnamyl alcohol from cinnamaldehyde with NaBH4Draw 1,2-hydride addition to the aldehyde carbon of cinnamaldehyde and protonation by methanol, leaving the conjugated C=C untouched.
- Cyclohexanol from cyclohexanone with NaBH4Draw hydride transfer from borohydride to the carbonyl carbon of cyclohexanone, then protonation of the alkoxide by methanol.
- Ninhydrin from indane-1,2,3-trione and waterDraw water adding to the central carbonyl carbon of indane-1,2,3-trione and the two proton transfers that give the gem-diol ninhydrin.
- Acid Peterson elimination: β-hydroxysilane to (Z)-oct-4-eneDraw sulfuric acid protonating the hydroxyl of (4S,5S)-5-(trimethylsilyl)octan-4-ol and the anti elimination of water and the silyl group to (Z)-oct-4-ene.
- Base Peterson elimination: β-hydroxysilane to (E)-oct-4-eneDraw potassium hydride deprotonating (4S,5S)-5-(trimethylsilyl)octan-4-ol, the alkoxide closing onto silicon and the syn fragmentation to (E)-oct-4-ene.
- Peterson olefination: benzophenone to 1,1-diphenyletheneDraw (trimethylsilyl)methyllithium adding to benzophenone, protonation to the β-hydroxysilane and the KH-promoted elimination to 1,1-diphenylethene.
- 1-Phenylcyclopentan-1-ol from phenyllithiumDraw phenyllithium adding to cyclopentanone and the NH4Cl workup that gives the tertiary alcohol 1-phenylcyclopentan-1-ol.
- Schlosser Wittig: butanal to (E)-hex-2-eneDraw the Schlosser sequence: ylide addition to butanal, PhLi deprotonation to the β-oxido ylide, protonation by HCl, ring closure and collapse to (E)-hex-2-ene.
- Still–Gennari: benzaldehyde to methyl (Z)-cinnamateDraw KHMDS deprotonating the bis(trifluoroethyl) phosphonoacetate, addition to benzaldehyde, ring closure and fast collapse to methyl (Z)-cinnamate.
- Thiamine-catalysed benzoin: furfural to furoinDraw how the thiamine ylide turns furfural into an acyl anion equivalent (the Breslow intermediate) that couples with a second furfural to give furoin.
- Tishchenko reaction: acetaldehyde to ethyl acetateDraw how aluminium ethoxide turns two acetaldehyde molecules into ethyl acetate through a hemiacetal alkoxide and an intramolecular hydride transfer.
- Tishchenko reaction: benzaldehyde to benzyl benzoateDraw the aluminium-mediated alkoxide addition and the intramolecular hydride transfer that couple two benzaldehyde molecules into benzyl benzoate.
- TMS cyanohydrin of acetophenone from TMSCN and ZnI2Draw ZnI2 activating trimethylsilyl cyanide, silyl transfer to the carbonyl oxygen of acetophenone, cyanide addition and release of the zinc catalyst.
- Mandelonitrile by HCN transfer from acetone cyanohydrinDraw Et3N deprotonating acetone cyanohydrin, loss of cyanide to give acetone, cyanide adding to benzaldehyde and protonation to mandelonitrile.
- 1-Vinylcyclohexan-1-ol from vinylmagnesium bromideDraw vinylmagnesium bromide adding to cyclohexanone and the NH4Cl workup that gives the tertiary allylic alcohol 1-vinylcyclohexan-1-ol.
- Wittig: 4-methoxybenzaldehyde to 4-methoxystyreneDraw methylenetriphenylphosphorane and 4-methoxybenzaldehyde forming the oxaphosphetane in one step and its collapse to 4-methoxystyrene.
- Stabilized Wittig: benzaldehyde to ethyl (E)-cinnamateDraw the ester-stabilized ylide adding to benzaldehyde, oxaphosphetane formation and collapse to ethyl (E)-cinnamate; explain why E forms.
- Wittig reaction: benzaldehyde to (E)-stilbeneDraw the benzylidene ylide adding to benzaldehyde, oxaphosphetane formation and collapse to (E)-stilbene and triphenylphosphine oxide.
- Wittig reaction: cyclohexanone to benzylidenecyclohexaneDraw benzylidenetriphenylphosphorane adding to cyclohexanone, closure to the oxaphosphetane and collapse to benzylidenecyclohexane and triphenylphosphine oxide.
- Salt-free Wittig: butanal to (Z)-hex-2-eneDraw the unstabilized ethylidene ylide and butanal closing directly to the cis oxaphosphetane and its collapse to (Z)-hex-2-ene.
- Wittig reaction: cyclohexanone to methylenecyclohexaneDraw the ylide carbon adding to cyclohexanone, ring closure to the oxaphosphetane and its collapse to methylenecyclohexane and triphenylphosphine oxide.
- Butyllithium makes methylenetriphenylphosphoraneDraw butyllithium removing a methyl hydrogen from methyltriphenylphosphonium and the two resonance forms (ylide and ylene) of the product.
Predict the product 10
- Grignard addition — ethylmagnesium bromide and acetonePredict alcohol connectivity after carbon nucleophile addition and a separate workup.
- Sodium acetylide adds to cyclopentanonePredict the tertiary propargylic alcohol formed when an acetylide adds to cyclopentanone.
- Cyanohydrin formation: HCN with cyclohexanonePredict the cyanohydrin formed when HCN adds to a cyclic ketone.
- Grignard addition: phenylmagnesium bromide and propanalPredict the secondary alcohol formed when an aryl Grignard reagent adds to an aldehyde.
- Pentan-2-one from butanoyl chloride and lithium dimethylcupratePredict the ketone formed when a Gilman reagent reacts with an acid chloride.
- Ozonolysis of 2-methylbut-2-ene: acetone and acetaldehydePredict the carbonyl fragments from reductive ozonolysis of a trisubstituted alkene.
- NaBH4 chemoselectivity: cinnamaldehyde C=C survivesPredict that sodium borohydride reduces the C=O of an α,β-unsaturated aldehyde and keeps the alkene.
- NaBH4 reduction of 2-methylcyclohexanonePredict the alcohol formed when sodium borohydride reduces an α-substituted cyclic ketone.
- NaBH4 selectivity: ketone vs ester in a keto esterDecide which carbonyl group of a keto ester sodium borohydride reduces.
- Ethylidene Wittig product from cyclohexanonePredict the alkene formed when ethylidenetriphenylphosphorane reacts with cyclohexanone.
Classify 12
- Evaluate a proposed carbonyl pathwayDistinguish carbonyl addition from acyl substitution using the groups attached to carbonyl carbon.
- Why butan-2-one adds a Grignard but does not substituteExplain why the tetrahedral intermediate from a ketone stays an alkoxide while the one from an ester expels a group.
- Alcohol class from the Grignard carbonyl partnerClassify the alcohol (primary, secondary or tertiary) that a Grignard reagent gives with formaldehyde, an aldehyde or a ketone.
- LiAlH4 and cyclohex-2-enone: 1,2- or 1,4-additionClassify the reduction of cyclohex-2-en-1-one by lithium aluminium hydride as 1,2- or 1,4-addition and name the product.
- Gem-diol from propanal: pick the hydrateRecognise the geminal diol (hydrate) formed when water adds across a C=O bond.
- Solvents for NaBH4 and LiAlH4 reductionsMatch sodium borohydride and lithium aluminium hydride to suitable reaction solvents and workups.
- IUPAC ketoneDraw a branched ketone from its name.
- Ring aldehydeName an aldehyde attached to a ring.
- Common namesMatch common names of simple carbonyl compounds.
- Diketone numberingName a compound with two ketone groups.
- Name the carbonylName a straight-chain aldehyde.
- Aldehyde outranks ketoneName a compound containing both an aldehyde and a ketone.
Compare 3
- Compare access to a carbonylUse both steric and electronic effects to compare simple carbonyl electrophiles.
- Rank hydration constants: chloral to acetoneRank four carbonyl compounds by the equilibrium constant for adding water to form a gem-diol.
- Rank carbonyl electrophilicityRank carbonyl compounds by reactivity toward nucleophiles.
Calculate 4
- Convert an addition equilibrium into a populationCalculate a two-state hydrate fraction from a supplied equilibrium ratio.
- Stereoisomers from NaBH4 reduction of (R)-3-methylcyclohexanoneCount the stereoisomeric alcohols formed when a new stereocentre is created next to an existing one in a ring.
- Percent hydrate from KCalculate the fraction of an aldehyde present as its hydrate.
- Hydrides per BH4⁻: moles of acetone reducedCalculate how many moles of ketone one mole of sodium borohydride can reduce.
Find the error 1
- Grignard reagent compatibility — water quenchRecognize acid–base quenching as a competing reaction of a carbon nucleophile.
Interpret the evidence 4
- Read a neutral carbonylDistinguish partial polarity from formal charge in a carbonyl.
- IR: tell pentanal from pentan-3-oneUse the aldehyde C–H stretch to distinguish an aldehyde from a ketone of the same formula.
- IR: which ketone absorbs at 1685 cm⁻¹Identify the conjugated ketone from a C=O stretching band lowered to about 1685 cm⁻¹.
- 1H NMR: the aldehyde singlet of 2,2-dimethylpropanalAssign a downfield 1H NMR singlet near 9.5 ppm to an aldehyde proton and explain its shift and multiplicity.
Work backward 3
- Work backward from a cyclic alcoholInfer a carbonyl precursor for hydride reduction without changing the carbon skeleton.
- Split an alkene into two carbon partnersRecover a carbonyl and a phosphorus ylide that preserve both sides of the target double bond.
- Choose the alkyl halide for a Wittig to 2-methylbut-2-eneWork backward from 2-methylbut-2-ene to the alkyl halide that makes the ylide needed with acetone.
Plan a synthesis 5
- Using mandelonitrile: hydrolysis and reductionMatch the two standard follow-up reactions of a cyanohydrin to their products.
- Hexanal from ethyl hexanoate with DIBAL-HChoose the reagent that reduces an ester only as far as the aldehyde.
- Hexanal from hex-1-yne by hydroboration–oxidationChoose the reagents that convert a terminal alkyne into an aldehyde with the same carbon chain.
- Hexan-2-one from hex-1-yne by mercury-catalysed hydrationChoose the reagents that convert a terminal alkyne into a methyl ketone.
- Preparing methylenetriphenylphosphorane for a WittigChoose the two-step sequence that makes the Wittig reagent Ph3P=CH2 from a phosphine and an alkyl halide.
Explain why 7
- Infer stereochemistry from an achiral environmentIdentify racemic product formation when addition creates one stereocenter.
- Why aryl aldehydes add more slowlyExplain the lower reactivity of aromatic aldehydes.
- Electron-poor carbonylExplain why electron-withdrawing groups favour hydrate formation.
- Why cyanohydrin formation needs a trace of baseExplain why a catalytic amount of base (or KCN) is needed for HCN to add to a carbonyl.
- NaBH4 reduction of butan-2-one: racemic butan-2-olExplain why reducing butan-2-one with sodium borohydride gives a racemic alcohol.
- Wittig versus Grignard and dehydration for methylenecyclohexaneExplain why a Wittig reaction, not Grignard addition followed by acid dehydration, is used to make methylenecyclohexane.
- Driving force of the Wittig: triphenylphosphine oxideIdentify what makes the Wittig reaction of benzaldehyde with Ph3P=CH2 thermodynamically favourable.
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