Organic Chemistry — Chapters 10, 11 & 17

Exam review: reaction examples, reagent recognition, nucleophile/base strength, steric bulk, and mechanism rules.

R01 [Ch 10] propene + HBr: predict the product and reaction type.

Propene gives 2-bromopropane. Electrophilic addition, Markovnikov; a carbocation intermediate is involved.

R02 [Ch 10] propene + HCl: predict the product and reaction type.

Propene gives 2-chloropropane. Markovnikov electrophilic addition; HCl is an acid, not a base.

R03 [Ch 10] propene + HBr, ROOR: predict the product and reaction type.

Propene gives 1-bromopropane. Anti-Markovnikov radical addition. The useful peroxide effect does not apply to HCl.

R04 [Ch 10] propene + NBS, light: predict the product and reaction type.

Propene gives allyl bromide. Radical substitution replaces an allylic H with Br. Keep the double bond.

R05 [Ch 10] bromoethane + Mg, dry ether: predict the product and reaction type.

Bromoethane gives ethylmagnesium bromide. Metal insertion/redox reverses carbon polarity. Product: strong carbon nucleophile and very strong base.

R06 [Ch 11] 1-bromopropane + NaCN, DMF: predict the product and reaction type.

1-Bromopropane gives butanenitrile by SN2. CN- is a strong nucleophile and relatively weak base for E2 selection. Adds one carbon.

R07 [Ch 11] 1-bromopropane + NaN3, acetone: predict the product and reaction type.

1-Bromopropane gives 1-azidopropane by SN2. N3- is a strong, nonbulky nucleophile and weak base.

R08 [Ch 11] 1-bromopropane + NaI, acetone: predict the product and reaction type.

1-Bromopropane gives 1-iodopropane by SN2. I- is a good nucleophile and very weak base.

R09 [Ch 11] bromoethane + NaOH, aqueous; primary substrate: predict the product and reaction type.

Bromoethane gives ethanol by SN2 under substitution-favoring conditions. OH- is strong, nonbulky, and both nucleophilic and basic.

R10 [Ch 11] bromoethane + NaOCH3: predict the product and reaction type.

Bromoethane gives methoxyethane by SN2. Methoxide is a strong nucleophile and strong, small base; substrate affects competition.

R11 [Ch 11] 2-bromo-2-methylbutane + NaOEt, EtOH, heat: predict the product and reaction type.

2-Bromo-2-methylbutane gives mainly 2-methyl-2-butene by E2. Ethoxide is strong and relatively small. Tertiary carbon excludes SN2; minor alkene omitted.

R12 [Ch 11] 2-bromo-2-methylbutane + KOtBu: predict the product and reaction type.

2-Bromo-2-methylbutane favors 2-methyl-1-butene by E2 with bulky tert-butoxide. Hofmann product shown; minor alkene omitted.

R13 [Ch 11] tert-butyl bromide + H2O; substitution pathway: predict the product and reaction type.

tert-Butyl bromide gives tert-butanol through carbocation formation then water attack. Water is a weak Nu/base; E1 can compete.

R14 [Ch 11] 4-bromobutan-1-olate + Internal alkoxide attacks C-Br: predict the product and reaction type.

4-Bromobutan-1-olate closes to a five-membered cyclic ether, tetrahydrofuran. Count O as one ring atom.

R15 [Ch 11] propyne + NaNH2: predict the product and reaction type.

Propyne is deprotonated to an acetylide. Acid-base reaction; NH2- is a very strong, nonbulky base. NH3 coproduct omitted.

R16 [Ch 11] propynide + bromoethane + Primary alkyl halide: predict the product and reaction type.

Propynide plus bromoethane gives pent-2-yne by SN2 C-C bond formation. Acetylide is a strong carbon nucleophile/base.

R17 [Ch 11] 4-hydroxypentan-2-one + Base, heat: predict the product and reaction type.

A beta-hydroxy ketone loses water overall to give an alpha,beta-unsaturated ketone. Remove alpha-H first, form enolate, then lose beta-OH. Alkene geometry unspecified.

R18 [Ch 17] propene + 1. BH3 2. H2O2, OH-: predict the product and reaction type.

Propene gives propan-1-ol. Anti-Markovnikov hydration; net syn addition, no carbocation rearrangement.

R19 [Ch 17] propene + 1. Hg(OAc)2, H2O 2. NaBH4: predict the product and reaction type.

Propene gives propan-2-ol. Markovnikov hydration without ordinary carbocation rearrangement.

R20 [Ch 17] propene + H3O+: predict the product and reaction type.

Propene gives propan-2-ol. Electrophilic addition through a carbocation; rearrangements are possible on other substrates.

R21 [Ch 17] propan-1-ol + PBr3: predict the product and reaction type.

Propan-1-ol gives 1-bromopropane. Activate oxygen then SN2 at carbon. At a stereocenter, inversion occurs.

R22 [Ch 17] propan-1-ol + SOCl2, pyridine: predict the product and reaction type.

Propan-1-ol gives 1-chloropropane. SN2 at carbon after activation; inversion at a stereocenter with pyridine.

R23 [Ch 17] propan-1-ol + TsCl, pyridine: predict the product and reaction type.

Alcohol becomes propyl tosylate, a good leaving-group substrate. Substitution at sulfur retains the original C-O bond and configuration at carbon.

R24 [Ch 17] propan-1-ol + TMSCl, pyridine: predict the product and reaction type.

Propan-1-ol becomes a trimethylsilyl ether. Protection removes the acidic O-H proton; reaction is substitution at silicon.

R25 [Ch 17] trimethylsilyl ether of propan-1-ol + Aqueous acid: predict the product and reaction type.

Trimethylsilyl ether gives propan-1-ol. Deprotection restores OH; not carbon SN1/SN2 classification.

R26 [Ch 17] 2-methylbutan-2-ol + H3PO4, heat: predict the product and reaction type.

2-Methylbutan-2-ol gives mainly 2-methyl-2-butene by E1. Protonate OH, lose water, remove beta-H. Minor alkene omitted.

R27 [Ch 17] propanal + NaBH4; protonation/workup: predict the product and reaction type.

Propanal gives propan-1-ol. Hydride addition/reduction; aldehyde becomes primary alcohol.

R28 [Ch 17] butan-2-one + NaBH4; protonation/workup: predict the product and reaction type.

Butan-2-one gives butan-2-ol. Ketone reduction gives secondary alcohol; racemic with achiral reagents. Stereochemistry not drawn.

R29 [Ch 17] methyl propanoate + 1. LiAlH4 2. aqueous workup: predict the product and reaction type.

Methyl propanoate gives propan-1-ol plus methanol. LAH reduces ester carbonyls; NaBH4 normally does not under standard introductory conditions.

R30 [Ch 17] propanoic acid + 1. LiAlH4 2. aqueous workup: predict the product and reaction type.

Propanoic acid gives propan-1-ol by reduction. LAH is a powerful hydride reducing agent.

R31 [Ch 17] ethanal + 1. EtMgBr 2. H3O+: predict the product and reaction type.

Ethanal plus ethylmagnesium bromide gives butan-2-ol. Nucleophilic carbonyl addition followed by protonation; secondary alcohol, racemic.

R32 [Ch 17] acetone + 1. EtMgBr 2. H3O+: predict the product and reaction type.

Acetone gives 2-methylbutan-2-ol. Nucleophilic carbonyl addition gives a tertiary alcohol.

R33 [Ch 17] methyl acetate + 1. excess EtMgBr 2. H3O+: predict the product and reaction type.

Methyl acetate gives 3-methylpentan-3-ol. Two ethyl groups add: first addition/collapse gives a ketone, then another addition. Methanol byproduct omitted.

R34 [Ch 17] formaldehyde + 1. EtMgBr 2. H3O+: predict the product and reaction type.

Formaldehyde gives propan-1-ol. Grignard addition to formaldehyde gives a primary alcohol with one extra carbon.

R35 [Ch 17] ethanol + methylmagnesium bromide + Free alcohol + Grignard: predict the product and reaction type.

Ethanol protonates methylmagnesium bromide, giving methane and a magnesium alkoxide. The diagram abbreviates the alkoxide as O- and omits its magnesium counterion. Acid-base, not NR.

R36 [Ch 17] ethanol + NaH: predict the product and reaction type.

Ethanol gives sodium ethoxide plus H2 gas. Acid-base reaction. NaH is a strong base, not the usual carbonyl reducing agent; counterion/byproduct omitted.

R37 [Ch Review] but-2-yne + H2, Lindlar catalyst: predict the product and reaction type.

But-2-yne gives cis-(Z)-but-2-ene by partial reduction with syn addition.

R38 [Ch Review] but-2-yne + Li or Na, liquid NH3: predict the product and reaction type.

But-2-yne gives trans-(E)-but-2-ene by partial reduction; net anti addition.

R39 [Ch Review] ethene + Peroxyacid, RCO3H: predict the product and reaction type.

Ethene gives oxirane. Concerted epoxidation/oxidation; the peroxyacid transfers oxygen.

R40 [Ch Review] oxirane + H2O, H+: predict the product and reaction type.

Oxirane gives ethane-1,2-diol. Epoxide ring opening; attack is backside, though this symmetric example has no stereocenters.

R41 [Ch Review] styrene + Chiral osmium-based system: predict the product and reaction type.

Styrene gives an enantioenriched vicinal diol by syn dihydroxylation. One possible major enantiomer is pictured; ligand choice determines which enantiomer is favored.

C01 OH-: nucleophile, base and bulk?

Strong nucleophile, strong nonbulky base. SN2/E2 depend on substrate and conditions.

C02 Methoxide and ethoxide: classify.

Strong nucleophiles and strong relatively small bases. SN2/E2 competition.

C03 tert-Butoxide: classify.

Strong bulky base; poor SN2 nucleophile because of crowding. Usually favors E2.

C04 CN- and N3-: classify.

Strong, nonbulky nucleophiles; relatively weak bases for ordinary E2 prediction.

C05 Water, methanol and ethanol: classify.

Weak neutral nucleophiles and weak nonbulky bases. SN1/E1 can occur with a suitable substrate.

C06 Is methanol the same as methoxide?

No. CH3OH is weak/neutral; CH3O- is a strong nucleophile and strong base.

C07 Grignard RMgX: classify and name its key incompatibility.

Strong carbon nucleophile and very strong base; bulk depends on R. Free OH consumes it by proton transfer.

C08 Pyridine: role in alcohol activation?

Relatively nonbulky weak base; can also be nucleophilic. Removes protons/neutralizes acid in these reactions.

C09 SN2: arrow pattern and stereochemistry?

Nu to carbon; C-LG bond to LG simultaneously. Backside attack gives inversion; no carbocation rearrangement.

C10 SN1: sequence and stereochemistry?

LG leaves, planar carbocation forms, Nu attacks; deprotonate if needed. Both faces can react; not necessarily a perfect racemate.

C11 E2: what three arrows are drawn together?

Base to beta-H; C-H electrons to C-C to form C=C; C-LG electrons to LG.

C12 Cyclohexane E2: which bond becomes double?

The bond connecting the LG-bearing carbon to the adjacent carbon whose axial H is anti to the axial LG.

C13 Chair flip: what changes and what stays?

Axial and equatorial swap; up/down and cis/trans stay the same.

C14 E1 versus E1cB: which event is first?

E1: LG leaves first to form a cation. E1cB: H is removed first to form a stabilized anion.

C15 Zaitsev versus Hofmann?

Zaitsev = more substituted alkene. Hofmann = less substituted. Small bases often favor Zaitsev; bulky bases often favor Hofmann. Geometry can override.

C16 Markovnikov versus anti-Markovnikov?

For typical HX/hydration examples, X/OH goes to the more substituted carbon in Markovnikov and less substituted carbon in anti-Markovnikov.

C17 Can a tertiary substrate do SN2?

No ordinary SN2: the carbon is too crowded. Strong base may give E2; ionizing conditions may allow SN1/E1.

C18 Two successive SN2 steps: stereochemical result?

Two inversions give overall retention of spatial configuration. R/S labels must still be reassigned.

C19 Tosylation then SN2: stereochemical result?

Tosylation retains configuration at carbon; SN2 inverts. Overall inversion.

C20 Polar protic solvents in the guide?

Water, methanol and ethanol. They hydrogen-bond and can favor ionization for SN1/E1.

C21 Polar aprotic solvents in the guide?

DMF, DMSO, acetone and acetonitrile (MeCN). Often favor anionic SN2. Ethyl acetate is moderately polar aprotic.

C22 DMS versus DMSO?

DMS is dimethyl sulfide: nucleophilic sulfur, weak base, less polar. DMSO is dimethyl sulfoxide: strongly polar aprotic solvent.

C23 Why use dry ether for Grignard formation?

Ether coordinates magnesium; absence of water prevents acid-base destruction of the reagent.

C24 Which is more acidic: phenol or a typical alcohol?

Phenol, because phenoxide is resonance-stabilized. Approximate pKa: phenol 10, ordinary alcohol 16-18.

C25 How does nitro substitution affect phenol acidity?

Usually increases acidity. Ortho/para can stabilize phenoxide by resonance plus induction; meta mainly by induction.

C26 Does every reagent need an SN1/SN2/E1/E2 label?

No. Addition, oxidation, reduction, protection and acid-base reactions have other mechanisms.

C27 Are direct Grignard + alkyl-halide couplings a general SN2 rule?

No. Your course drawings simplify this; reliable coupling generally needs appropriate reagents/catalysts. Do not confuse it with standard carbonyl addition.

C28 Alkene stability and carbocation stability?

Comparable alkenes: tetra > tri > di > mono substituted. Comparable alkyl cations: tertiary > secondary > primary > methyl; resonance also matters.