Química Orgânica 1 · Exam review
Radicais, álcoois e éteres
Uma lição resolvida gratuita e 104 problemas de prática em que você mesmo desenha cada seta curva.
Travou em radicais, álcoois e éteres? Escaneie o problema.
Tire uma foto da reação da sua lista ou do livro e desenhe o mecanismo com cada seta corrigida. 1 scan grátis agora, sem cadastro; mais 1 com uma conta gratuita.
Depois, Scan Standard: /mês
Prática grátis de setas curvas: escolha um mecanismo
Toque em um para ver cada seta curva, passo a passo. Nas demos, você mesmo as desenha, sem cadastro.
- 1-Chloropropane from propan-1-ol and SOCl2
- Radical chlorination of cyclohexane
- Selective photobromination of 2,3-dimethylbutane
- Radical chain addition of HBr to styrene
- Anti-Markovnikov addition of HBr to 2-methylpropene with a peroxide
- SN1 conversion of 2-methylbutan-2-ol to 2-chloro-2-methylbutane
- PBr₃ converts 2-methylpropan-1-ol to 1-bromo-2-methylpropane
- Butan-1-ol to pentanenitrile through the tosylate
- HBr cleaves anisole to phenol and bromomethane
O que você vai aprender
- Draw radical chain halogenation and peroxide-initiated HBr addition with fishhook arrows, and predict their products.
- Predict halogenation product ratios from the number of hydrogens and their relative reactivity, and explain why bromination is more selective than chlorination.
- Choose between HX, PBr₃, SOCl₂ and TsCl to turn an alcohol into a halide or sulfonate, and predict rearrangement and stereochemistry.
- Plan a Williamson ether synthesis and predict which C–O bond an acid cleaves.
- Predict the site and stereochemistry of epoxide opening under basic and acidic conditions.
Lição gratuita
O texto da lição resolvida. No Arrow Lab, cada etapa vem com as estruturas e as setas desenhadas.
Ler a aula gratuita (7 partes)
Radical chains: initiation, propagation, termination
Light or heat breaks a weak bond (Cl–Cl, Br–Br or the O–O bond of a peroxide) homolytically: one electron goes to each atom, shown with two fishhook arrows. In propagation a halogen atom removes a hydrogen from carbon to give H–X and a carbon radical, and the carbon radical removes a halogen atom from X₂ to give the alkyl halide and a new halogen atom. Each propagation step consumes one radical and makes one, so one initiation event converts many molecules. Termination joins two radicals and stops a chain. Cyclohexane, whose twelve hydrogens are all equivalent, gives a single monochloride, chlorocyclohexane.
Selectivity: count the hydrogens, then weigh their reactivity
The amount of each monohalide is proportional to (number of equivalent hydrogens) × (relative reactivity per hydrogen). For chlorination at 25 °C the factors are about 1 : 3.9 : 5.0 for primary : secondary : tertiary C–H, so chlorine gives mixtures. For bromination at 125 °C they are about 1 : 82 : 1600, so bromine attacks the weakest C–H bond almost exclusively. The reason is the Hammond postulate: abstraction of H by Br• is endothermic (H–Br, about 366 kJ/mol, is weaker than any C–H bond), so its transition state is late and resembles the carbon radical; differences in radical stability (tertiary > secondary > primary > methyl, with allylic and benzylic radicals more stable still) are felt almost fully. Abstraction by Cl• is nearly thermoneutral or exothermic, its transition state is early, and it discriminates little. In 2-methylbutane, drawn here, bromination gives mainly 2-bromo-2-methylbutane.
Peroxides reverse the regiochemistry of HBr addition
Without peroxides, HBr adds by protonation to the more stable carbocation (Markovnikov). With a peroxide initiator, an alkoxyl radical removes H from HBr to make Br•, and Br• adds to the less substituted alkene carbon so that the more stable carbon radical forms. That radical takes H from another HBr, giving the anti-Markovnikov bromide and a new Br•. 2-Methylpropene therefore gives 1-bromo-2-methylpropane, drawn here. Only HBr behaves this way: with HCl the H transfer from the strong H–Cl bond is too slow, and with HI the addition of I• to the alkene is uphill.
Turning OH into a leaving group
Hydroxide is a poor leaving group, so an alcohol must be activated. Strong acid (HCl, HBr) protonates the OH so that water leaves: tertiary alcohols react by SN1 through a carbocation, primary alcohols by SN2 on the protonated alcohol, and any carbocation can rearrange. PBr₃ and SOCl₂ with pyridine convert the oxygen into a leaving group that halide displaces by SN2, so no carbocation forms, no rearrangement occurs and a stereocentre bearing the OH is inverted. TsCl with pyridine makes a tosylate without touching the C–O bond, so configuration is retained; a later SN2 on the tosylate inverts it. The drawing shows (R)-butan-2-yl tosylate, made from (R)-butan-2-ol with retention.
Making and breaking ethers
In a Williamson synthesis an alkoxide or phenoxide displaces a halide or tosylate by SN2, so the electrophile must be methyl or primary; a secondary or tertiary halide meets a strongly basic alkoxide and eliminates. Put the hindered group on the oxygen. Ordinary alcohols are deprotonated with NaH; phenols are acidic enough for NaOH. When the alkoxide and the leaving group are in one molecule, five- and six-membered rings close rapidly. Ethers are cleaved by HBr or HI: the oxygen is protonated, then halide attacks by SN2 at the less hindered carbon (a methyl group first), or the C–O bond ionises by SN1 if one carbon is tertiary. An aryl C–O bond is never broken, so aryl methyl ethers give a phenol and a methyl halide. Cyclohexyl methyl ether, drawn here, gives cyclohexanol and iodomethane with one equivalent of HI.
Opening epoxides: base versus acid
An epoxide carries about 110 kJ/mol of ring strain, so it opens with nucleophiles that leave ordinary ethers untouched. Strong nucleophiles (alkoxides, hydroxide, Grignard reagents, LiAlH₄, azide) attack by SN2 at the less hindered carbon. In acid the oxygen is protonated first; the C–O bond to the more substituted carbon is longer and that carbon carries more positive charge, so a weak nucleophile such as methanol or water attacks the more substituted carbon. Either way the nucleophile enters from the side opposite the oxygen, so ring epoxides give trans products and the attacked stereocentre is inverted. 2,2-Dimethyloxirane, drawn here, gives 1-methoxy-2-methylpropan-2-ol with sodium methoxide but 2-methoxy-2-methylpropan-1-ol with methanol and acid.
What to carry forward
For radical halogenation, multiply hydrogen count by reactivity and remember that bromine is the selective halogen; peroxides make HBr add anti-Markovnikov through the more stable carbon radical. For alcohols, choose PBr₃, SOCl₂ or TsCl to avoid carbocations and control stereochemistry, and HX when SN1 is acceptable. Build ethers with the alkoxide on the hindered side and cleave them at the methyl, tertiary or non-aryl carbon. Open epoxides at the less hindered carbon with strong nucleophiles and at the more substituted carbon in acid, always from the back side.
Problemas de prática (104)
Praticar é grátis com uma conta. Leia a solução de cada problema
Desenhe o mecanismo 60
Radical halogenation
- Radical chlorination of cyclohexaneDraw the initiation and both propagation steps of the light-driven chlorination of cyclohexane with fishhook arrows, and explain why only one monochloride forms.
- Selective photobromination of 2,3-dimethylbutaneDraw the light-initiated radical bromination of 2,3-dimethylbutane with fishhook arrows and explain why bromine replaces a tertiary hydrogen.
- Radical chain addition of HBr to styreneDraw the two propagation steps of peroxide-initiated HBr addition to styrene with fishhook arrows: bromine-atom addition to the CH₂ end and hydrogen transfer from HBr to the benzylic radical.
- Anti-Markovnikov addition of HBr to 2-methylpropene with a peroxideDraw the radical chain in which a peroxide initiator makes Br•, Br• adds to the CH₂ end of 2-methylpropene, and the tertiary radical takes H from HBr to give 1-bromo-2-methylpropane.
- 2-Bromo-2-methylpentane by radical brominationDraw the initiation and both propagation steps of the light-driven bromination of 2-methylpentane with fishhook arrows, and explain why the tertiary hydrogen is replaced.
- 1-Chloro-1-methylcyclopentane by radical chlorinationDraw the chain that converts methylcyclopentane into 1-chloro-1-methylcyclopentane with fishhook arrows, and explain why chlorination gives a mixture.
- 1-Chloro-2,2-dimethylpropane from neopentaneDraw the light-driven chlorination of neopentane with fishhook arrows and explain why it gives a single monochloride.
Alcohols to halides and sulfonates
- SN1 conversion of 2-methylbutan-2-ol to 2-chloro-2-methylbutaneDraw the SN1 conversion of 2-methylbutan-2-ol into 2-chloro-2-methylbutane in concentrated hydrochloric acid: protonation, loss of water and capture of the tertiary cation by chloride.
- PBr₃ converts 2-methylpropan-1-ol to 1-bromo-2-methylpropaneDraw how PBr₃ turns the OH of 2-methylpropan-1-ol into a leaving group and how bromide displaces it by SN2 without rearrangement.
- Butan-1-ol to pentanenitrile through the tosylateDraw the tosylation of butan-1-ol with TsCl and pyridine, then the SN2 displacement of tosylate by cyanide that gives pentanenitrile.
- 1-Bromo-1-methylcyclohexane from 1-methylcyclohexanol and HBrDraw the SN1 conversion of 1-methylcyclohexan-1-ol into 1-bromo-1-methylcyclohexane with HBr.
- Bromocyclohexane from cyclohexanol and PBr3Draw how PBr3 converts the OH of cyclohexanol into a leaving group and how bromide then displaces it (cyclohexanol).
- 1-Chloropropane from propan-1-ol and SOCl2Draw the formation of the alkyl chlorosulfite from propan-1-ol and SOCl2 and its SN2 displacement by chloride that gives 1-chloropropane.
- Azidocyclopentane from cyclopentanol via its tosylateDraw the tosylation of cyclopentanol and the SN2 displacement of the tosylate by azide that gives azidocyclopentane.
Ether synthesis and cleavage
- HBr cleaves anisole to phenol and bromomethaneDraw the protonation of anisole by HBr and the SN2 attack of bromide on the methyl carbon that gives phenol and bromomethane, and explain why the aryl C–O bond survives.
- Intramolecular Williamson synthesis of oxolane from 4-chlorobutan-1-olDraw the deprotonation of 4-chlorobutan-1-ol by hydroxide and the intramolecular SN2 that closes the five-membered ring of oxolane.
- Williamson synthesis of methoxycyclohexaneDraw the deprotonation of cyclohexanol by sodium hydride and the SN2 attack of the cyclohexoxide ion on iodomethane that gives methoxycyclohexane.
- Ethoxycyclohexane by alkoxymercuration of cyclohexeneDraw the alkoxymercuration of cyclohexene in ethanol and the NaBH4 demercuration that gives ethoxycyclohexane.
- 1,4-Dibromobutane from oxolane and excess HBrDraw both acid-promoted SN2 cleavages that turn oxolane (THF) into 1,4-dibromobutane with excess HBr.
- Phenol and iodoethane from ethoxybenzene and HIDraw the acidic cleavage of ethoxybenzene by HI and show which C–O bond breaks.
- tert-Butyl methyl ether from tert-butanol and methanolDraw the acid-catalysed SN1 formation of tert-butyl methyl ether from tert-butanol in methanol.
- Benzyl isopropyl ether by Williamson synthesisDraw the deprotonation of propan-2-ol by NaH and the SN2 attack of the alkoxide on benzyl bromide.
Epoxide ring opening
- Acid-catalysed methanolysis of 2,2-dimethyloxirane at the tertiary carbonDraw the acid-catalysed opening of 2,2-dimethyloxirane in methanol: protonation by CH₃OH₂⁺, attack of methanol at the tertiary carbon and deprotonation that gives 2-methoxy-2-methylpropan-1-ol.
- Methoxide opens 2,2-dimethyloxirane at the CH₂ carbonDraw the SN2 opening of 2,2-dimethyloxirane by methoxide at the less hindered carbon and the proton transfer from methanol that gives 1-methoxy-2-methylpropan-2-ol.
- 1-Aminopropan-2-ol from 2-methyloxirane and ammoniaDraw the SN2 opening of 2-methyloxirane by ammonia at the CH₂ carbon and the proton transfers that give 1-aminopropan-2-ol.
- trans-2-Azidocyclohexan-1-ol from cyclohexene oxideDraw the anti opening of cyclohexene oxide by azide and the protonation that gives trans-2-azidocyclohexan-1-ol.
- 1-Bromopropan-2-ol from 2-methyloxirane and HBrDraw the protonation of 2-methyloxirane by HBr and the opening by bromide that gives 1-bromopropan-2-ol.
- 2-Methoxy-2-phenylethan-1-ol from styrene oxide in acidic methanolDraw the acid-catalysed opening of 2-phenyloxirane by methanol at the benzylic carbon.
Halogenação radicalar
- 2-Bromo-2-metil-hexano por bromação radicalarDesenhe a cadeia radicalar que converte o 2-metil-hexano em 2-bromo-2-metil-hexano com Br2 e luz, e explique a seletividade do átomo de bromo.
- 1-(1-Bromoetil)-4-metilbenzeno racêmico a partir do 4-etiltoluenoDesenhe a cadeia radicalar que broma a posição benzílica secundária do 4-etiltolueno com Br2 e luz, e explique por que o produto é racêmico.
- 1-Bromo-1-etilciclopentano por bromação radicalarDesenhe a iniciação e as duas etapas de propagação que transformam o etilciclopentano em 1-bromo-1-etilciclopentano com Br2 e luz.
- Bromação benzílica do isobutilbenzeno com Br2 e luzDesenhe a cadeia radicalar que broma o isobutilbenzeno com Br2 e luz, e explique por que é o hidrogênio benzílico, e não o terciário, que é substituído.
- Bromação racêmica do (S)-1-cloro-2-metilbutanoDesenhe a bromação do (S)-1-cloro-2-metilbutano em seu estereocentro com Br2 e luz, e explique por que o 2-bromo-1-cloro-2-metilbutano formado é racêmico.
- Cloração do 2,2-dimetilbutano: três monocloretosDesenhe as três abstrações de hidrogênio na cloração do 2,2-dimetilbutano com Cl2 e luz e calcule a porcentagem de cada monocloreto.
- Cloração do pentano: três monocloropentanosDesenhe a cloração do pentano em C1, C2 e C3 com Cl2 e luz e preveja a proporção de 1-cloropentano, 2-cloropentano e 3-cloropentano.
Bromação alílica com NBS
- 1-Bromo-2,3-dimetilbut-2-eno por bromação alílica com NBSDesenhe a cadeia radicalar que converte o 2,3-dimetilbut-2-eno em 1-bromo-2,3-dimetilbut-2-eno com NBS e luz.
- Bromação alílica do but-1-eno: dois brometos alílicosDesenhe a bromação do but-1-eno com NBS e luz, incluindo a ressonância do radical alílico, para explicar por que se formam tanto o 3-bromobut-1-eno quanto o (E)-1-bromobut-2-eno.
- 3-Bromociclo-hepteno por bromação alílica com NBSDesenhe a cadeia radicalar que converte o ciclo-hepteno em 3-bromociclo-hepteno com NBS e luz, usando setas de meia ponta.
Allylic bromination with NBS
- 3-Bromocyclopentene by allylic brominationDraw the radical chain that converts cyclopentene into 3-bromocyclopentene with NBS and light, using fishhook arrows.
De álcoois a haletos e sulfonatos
- 2-Cloro-2-fenilbutano racêmico a partir do (S)-2-fenilbutan-2-olDesenhe a conversão SN1 do (S)-2-fenilbutan-2-ol em 2-cloro-2-fenilbutano com HCl concentrado e explique por que o produto é racêmico.
- Mesilação do (S)-4-fenilbutan-2-ol com MsCl e Et3NDesenhe a mesilação do (S)-4-fenilbutan-2-ol com MsCl e Et3N e explique por que o estereocentro mantém sua configuração.
- (S)-2-Bromo-4-metilpentano a partir do (R)-4-metilpentan-2-olDesenhe como o PBr3 ativa o OH do (R)-4-metilpentan-2-ol e como o brometo o desloca com inversão, gerando (S)-2-bromo-4-metilpentano.
- (S)-(4-Bromobutan-2-il)benzeno a partir do (S)-3-fenilbutan-1-olDesenhe a conversão do (S)-3-fenilbutan-1-ol em (S)-(4-bromobutan-2-il)benzeno com PBr3 e decida o que acontece com o estereocentro.
- PBr3 com trans-2-metilciclo-hexanol: o brometo cisDesenhe a conversão do trans-2-metilciclo-hexanol em cis-1-bromo-2-metilciclo-hexano com PBr3 e explique por que a relação no anel muda de trans para cis.
- (R)-3-Cloro-heptano a partir do (S)-heptan-3-ol com SOCl2Desenhe a conversão do (S)-heptan-3-ol em (R)-3-cloro-heptano com SOCl2 e piridina, mostrando onde a configuração em C3 é invertida.
- SN2 com cianeto no tosilato de cis-4-metilciclo-hexilaDesenhe o cianeto deslocando o tosilato do tosilato de cis-4-metilciclo-hexila e explique por que se forma o trans-4-metilciclo-hexano-1-carbonitrila.
- (R)-2-Etilpentanonitrila a partir do tosilato de (S)-hexan-3-ilaDesenhe o deslocamento SN2 do tosilato no tosilato de (S)-hexan-3-ila pelo cianeto e atribua a configuração da 2-etilpentanonitrila formada.
- (S)-2-Iodo-heptano a partir do tosilato de (R)-heptan-2-ila e NaIDesenhe a reação SN2 do tosilato de (R)-heptan-2-ila com iodeto de sódio em acetona e atribua a configuração do 2-iodo-heptano.
- Tosilação do (R)-5-metil-hexan-2-ol com retençãoDesenhe a tosilação do (R)-5-metil-hexan-2-ol com TsCl e piridina e explique por que C2 mantém sua configuração.
Epoxide formation from halohydrins
- 2,2-Dimethyloxirane from a bromohydrinDraw the deprotonation of 1-bromo-2-methylpropan-2-ol and the intramolecular SN2 that closes 2,2-dimethyloxirane.
Abertura de anel de epóxidos
- 3-Hidroxipentanonitrila a partir do 2-etiloxirano e cianetoDesenhe o cianeto abrindo o 2-etiloxirano no carbono CH2 e a protonação do tratamento (workup) que gera a 3-hidroxipentanonitrila.
- trans-2-Hidroxiciclo-hexano-1-carbonitrila por abertura de epóxidoDesenhe a abertura anti do óxido de ciclo-hexeno pelo cianeto e o tratamento que gera a trans-2-hidroxiciclo-hexano-1-carbonitrila.
- 2-Ciclo-hexiletan-1-ol a partir do brometo de ciclo-hexilmagnésioDesenhe o brometo de ciclo-hexilmagnésio abrindo o oxirano e o tratamento ácido que gera o 2-ciclo-hexiletan-1-ol.
- 1-(Etiltio)-2-metilpropan-2-ol a partir do 2,2-dimetiloxiranoDesenhe o etanotiolato abrindo o 2,2-dimetiloxirano no carbono CH2 e a transferência de próton que gera o 1-(etiltio)-2-metilpropan-2-ol.
- 3-(Metiltio)butan-2-ol a partir do cis-2,3-dimetiloxirano mesoDesenhe o metanotiolato abrindo o cis-2,3-dimetiloxirano meso com inversão e explique por que o 3-(metiltio)butan-2-ol se forma como racemato.
- (S)-1-(Metiltio)propan-2-ol a partir do (S)-2-metiloxiranoDesenhe o metanotiolato abrindo o (S)-2-metiloxirano no carbono CH2 e mostre por que o (S)-1-(metiltio)propan-2-ol mantém a configuração.
- 1-Fenilpropan-1-ol a partir do óxido de estireno e MeMgBrDesenhe o brometo de metilmagnésio abrindo o óxido de estireno no carbono CH2 e o tratamento que gera o 1-fenilpropan-1-ol.
- 1-Fenilpropan-2-ol a partir do 2-metiloxirano e PhMgBrDesenhe o brometo de fenilmagnésio abrindo o 2-metiloxirano no carbono CH2 e o tratamento que gera o 1-fenilpropan-2-ol.
- trans-2-(Feniltio)ciclo-hexan-1-ol a partir do óxido de ciclo-hexenoDesenhe a abertura anti do óxido de ciclo-hexeno pelo tiofenóxido e a transferência de próton do etanol que gera o trans-2-(feniltio)ciclo-hexan-1-ol.
- 1-Fenil-2-(feniltio)etan-1-ol a partir do óxido de estirenoDesenhe o tiofenóxido abrindo o óxido de estireno no carbono CH2 e a transferência de próton do etanol que gera o 1-fenil-2-(feniltio)etan-1-ol.
Preveja o produto 14
Radical halogenation
- Major product of brominating 2-methylbutanePredict the major monobromide from radical bromination of a branched alkane.
Alcohols to halides and sulfonates
- Neopentyl alcohol with HBrPredict the rearranged product formed when a neopentyl alcohol reacts with HBr.
- Stereochemistry of a tosylate–bromide sequenceTrack configuration through tosylation (retention) and SN2 displacement (inversion) of a chiral secondary alcohol.
Ether synthesis and cleavage
- Cleaving methoxycyclohexane with one equivalent of HIPredict which C–O bond of a methyl secondary-alkyl ether breaks with one equivalent of HI.
Epoxide ring opening
- Configuration after azide opens (R)-2-methyloxiranePredict regiochemistry and configuration when a nucleophile opens a chiral terminal epoxide at the carbon that is not a stereocentre.
- Stereochemistry of opening a cis-epoxideDeduce the stereoisomers formed by anti opening of a meso epoxide with hydroxide.
- Grignard reagent opens an epoxidePredict the alcohol formed when a Grignard reagent opens an unsymmetrical epoxide.
- LiAlH₄ opens 1-methylcyclohexene oxidePredict the alcohol formed when hydride opens an unsymmetrical epoxide.
- Acidic methanolysis of 1-methylcyclohexene oxidePredict the regiochemistry of acid-catalysed epoxide opening by a weak nucleophile on a trisubstituted epoxide.
- Methoxide opens 2-methyloxiranePredict the regiochemistry of base-promoted opening of an unsymmetrical epoxide by an alkoxide.
De álcoois a haletos e sulfonatos
- Produto principal do 3-metilbutan-2-ol com HBrPreveja o brometo rearranjado formado quando um álcool secundário vizinho a uma C–H terciária reage com HBr por SN1.
Wave 1 practice
- Tosylate then azide on (R)-butan-2-olTrack configuration through tosylation (retention) and SN2 displacement (inversion).
- Where methanol opens a protonated epoxidePredict the regiochemistry of acid-catalysed epoxide opening at a tertiary carbon.
Abertura de anel de epóxidos
- Onde o metanotiolato abre o óxido de 1-metilciclo-hexenoPreveja o sítio e a estereoquímica da abertura do óxido de 1-metilciclo-hexeno por tiolato em meio básico.
Classificar 2
Ether synthesis and cleavage
- How does a tert-butyl ether cleave?Classify the pathway by which HBr cleaves an ether that has a tertiary alkyl group.
Wave 1 practice
- Which hydrogen does a bromine radical remove?Identify the hydrogen a selective bromine radical abstracts from a branched alkane.
Comparar 5
Radical halogenation
- Rank carbon radicals by stabilityRank methyl, primary, secondary, tertiary and allylic radicals by stability from C–H bond dissociation energies.
Alcohols to halides and sulfonates
- Rank alcohols in the Lucas testRank primary, secondary and tertiary alcohols by their rate of SN1 reaction with HCl and ZnCl₂.
Ether synthesis and cleavage
- Rank Williamson electrophilesRank alkyl bromides by how well they give an ether with sodium ethoxide by SN2.
De álcoois a haletos e sulfonatos
- Ordene os grupos abandonadores do hidróxido ao triflatoOrdene hidróxido, haletos e sulfonatos pela capacidade como grupo abandonador para explicar por que o OH de um álcool precisa ser ativado.
Wave 1 practice
- Which route inverts (R)-octan-2-ol to the (S)-acetate?Count the bond-breaking events at the stereocenter to decide retention or inversion across reagent sequences.
Calcular 6
Radical halogenation
- Selectivity of bromine for a tertiary hydrogenCalculate the percentage of tertiary bromide from photobromination of 2-methylpropane using relative reactivity factors.
- Enthalpy of hydrogen abstraction by Br•Use bond dissociation energies to calculate the enthalpy change of a radical hydrogen-abstraction step.
- Product ratio in the chlorination of propaneCombine hydrogen counts with relative reactivity to predict the percentage of the secondary chloride from propane chlorination.
Halogenação radicalar
- Quantos monocloretos o 3-metilpentano forma?Conte os produtos de monocloração constitucionais do 3-metilpentano agrupando os hidrogênios equivalentes.
- Fração de cloreto terciário a partir do 2,2,3-trimetilbutanoPreveja a porcentagem de cloreto terciário na cloração do 2,2,3-trimetilbutano a partir do número de hidrogênios e das velocidades por hidrogênio.
Wave 1 practice
- Tertiary chloride share from chlorinating 2-methylpentaneCombine hydrogen counts with per-hydrogen reactivity to predict a radical chlorination product ratio.
Encontre o erro 2
Alcohols to halides and sulfonates
- Find the error in an HBr mechanismIdentify the flaw in a proposed SN1 mechanism for a primary alcohol reacting with HBr.
Síntese e clivagem de éteres
- O que dá errado com metóxido e brometo de terc-butila?Diagnostique por que um plano de Williamson com um haleto de alquila terciário leva à eliminação e escolha a desconexão que funciona para o éter terc-butil metílico.
Interprete as evidências 1
- Por que o HCl gera um cloreto benzílico opticamente inativoInterprete a perda de rotação óptica quando um álcool benzílico terciário quiral é convertido em seu cloreto com HCl.
Trabalhe de trás para frente 3
Alcohols to halides and sulfonates
- Which alcohol gives (R)-2-bromopentane with PBr₃?Work backwards through a PBr₃ substitution to the configuration of the starting alcohol.
Ether synthesis and cleavage
- Disconnect ethoxybenzeneChoose the Williamson disconnection for an aryl alkyl ether.
Síntese e clivagem de éteres
- Melhores precursores de Williamson para o etoxiciclo-hexanoEscolha o par alcóxido e haleto de alquila que forma o etoxiciclo-hexano por SN2, e não por eliminação.
Planeje uma síntese 4
Alcohols to halides and sulfonates
- Make a chloride with inversionChoose the reagent that converts a chiral secondary alcohol into the chloride with clean inversion.
Ether synthesis and cleavage
- Choose a precursor for oxaneChoose the halo-alcohol whose intramolecular Williamson reaction gives a six-membered cyclic ether.
Wave 1 practice
- Plan a Williamson synthesis of tert-butyl methyl etherChoose the alkoxide/halide pair that lets a Williamson ether synthesis proceed by SN2 rather than E2.
Abertura de anel de epóxidos
- Planeje o butan-1-ol a partir do bromoetano via epóxidoPlaneje uma extensão de cadeia de dois carbonos, de um haleto de alquila a um álcool primário, com um reagente de Grignard e oxirano.
Explique por quê 7
Radical halogenation
- Why bromination is more selective than chlorinationExplain the different selectivities of chlorination and bromination with the Hammond postulate.
- Why the peroxide effect works only for HBrExplain from the energetics of both propagation steps why peroxides reverse the regiochemistry of HBr addition but not of HCl or HI addition.
Alcohols to halides and sulfonates
- Why an OH group must be activatedExplain why an alcohol's OH must be protonated or converted into a sulfonate or phosphite ester before substitution.
Ether synthesis and cleavage
- NaH or NaOH for a Williamson synthesis?Use pKa values to explain why sodium hydride, not sodium hydroxide, is used to form an alkoxide from a simple alcohol.
Epoxide ring opening
- Why epoxides open but ethers do notExplain why epoxides react with strong nucleophiles under basic conditions while ordinary ethers do not.
- Benzylic opening of styrene oxide in acidExplain how acid-catalysed epoxide opening can occur at the more substituted carbon yet still with inversion.
Bromação alílica com NBS
- Por que o NBS broma o ciclo-hexeno no carbono alílicoExplique como a baixa concentração de Br2 gerada pelo NBS permite que a substituição radicalar alílica supere a adição eletrofílica ao ciclo-hexeno.
Travou em radicais, álcoois e éteres? Escaneie o problema.
Tire uma foto da reação da sua lista ou do livro e desenhe o mecanismo com cada seta corrigida. 1 scan grátis agora, sem cadastro; mais 1 com uma conta gratuita.
Depois, Scan Standard: /mês