Searchable Organic Synthesis Route Library

Reagents: 1. BH3·THF; 2. H2O2, NaOH(aq)

Hydroboration–oxidation gives anti-Markovnikov net hydration; B and H add syn before oxidation.

Reagents: 1. Hg(OAc)2, H2O; 2. NaBH4

Oxymercuration–demercuration provides Markovnikov hydration without a free carbocation rearrangement.

Reagents: 1. BH3·THF; 2. H2O2, NaOH(aq)

Terminal OH formation is consistent with anti-Markovnikov hydration of a terminal alkene.

Reagents: 1. Hg(OAc)2, H2O; 2. NaBH4

Addition gives 2-butanol; because the alkene is achiral, a racemic mixture can result when C2 becomes stereogenic.

Reagents: H2O, dilute H2SO4 (acid catalysis)

Cyclohexene is symmetric at the alkene; Markovnikov versus anti-Markovnikov location is not distinguishable.

Reagents: 1. BH3·THF; 2. H2O2, NaOH(aq)

Hydroboration–oxidation gives 2-methyl-1-propanol (a primary alcohol).

Reagents: PCC in dry CH2Cl2

Anhydrous PCC is a common classroom method for stopping at the aldehyde.

Reagents: CrO3, H2SO4, H2O (Jones)

Aqueous strong oxidation permits primary alcohol oxidation to the carboxylic acid.

Reagents: PCC in dry CH2Cl2

Oxidation of a secondary alcohol produces a ketone without breaking the carbon skeleton.

Reagents: PCC in dry CH2Cl2

The ring carbon carrying OH is secondary and forms a ring ketone on oxidation.

Reagents: 1. NaBH4, MeOH; 2. aqueous workup

NaBH4 supplies hydride to an aldehyde and workup protonates the alkoxide.

Reagents: 1. NaBH4, MeOH; 2. aqueous workup

Hydride addition then protonation gives the secondary alcohol.

Reagents: 1. NaH (ethoxide formation); 2. CH3I

Attack at methyl iodide is favorable for SN2 and avoids competing E2 at the methyl carbon.

Reagents: K2CO3, acetone; then CH3I

Phenoxide attacks methyl iodide at the methyl carbon; an sp2 aryl carbon is not a normal SN2 center.

Reagents: 1. NaH; 2. CH3CH2Br

SN2 is feasible at primary bromoethane; hindered electrophiles raise E2 competition.

Reagents: 1. NaH; 2. CH3I

Even though the alkoxide is secondary, the SN2 event occurs at unhindered methyl iodide.

Reagents: 1. NaH; 2. CH3I

A bulky tert-butoxide can displace iodide at a methyl carbon; SN2 at tertiary carbon is not viable.

Reagents: 1. NaH + tert-butanol; 2. CH3CH2Br

A primary ethyl halide supports SN2; tertiary tert-butyl bromide with alkoxide tends toward E2.

Reagents: 1. NaOH(aq), SN2 → 1-butanol; 2. aqueous Cr(VI) oxidant → butanoic acid

Primary bromide supports substitution; the resulting primary alcohol can be oxidized to acid.

Reagents: 1. strong base, heat (E2) → propene; 2. BH3·THF, then H2O2/NaOH

Hydroboration of propene installs OH at the terminal carbon; an SN2 substitution on 2-bromopropane would make the wrong positional alcohol.

Reagents: 1. HBr, ROOR → 1-bromobutane; 2. NaOCH2CH3 → ether

Radical HBr addition to terminal 1-butene is anti-Markovnikov; the primary bromide allows SN2 with ethoxide.

Reagents: 1. H2O, H2SO4 → cyclohexanol; 2. PCC → cyclohexanone

Cyclohexanol is a secondary alcohol; oxidation gives cyclohexanone.

Reagents: 1. Hg(OAc)2/H2O; NaBH4 → 2-butanol; 2. PCC → 2-butanone

The alcohol must be at C2 to give the target 2-butanone; oxidation does not move the carbonyl position.

Reagents: 1. BH3·THF; H2O2/NaOH → 2-methyl-1-propanol; 2. PCC → 2-methylpropanal

Anti-Markovnikov hydration builds a primary alcohol that PCC oxidizes to the aldehyde.