Octet

Octet / Reactions

Alcohol to Alkyl Bromide (PBr₃)

Alcohol to Alkyl Bromide (PBr₃) (Substitution). Starts from Ethanol with PBr₃. Stereochemistry: Inversion (SN2 mechanism). Mechanism in 3 steps.

Substitution

Reaction details

Name

Alcohol to Alkyl Bromide (PBr₃)

Type

Substitution

Starting Material

CCO

Product

CCBr

Reagents

  • PBr₃

Mechanism
  1. Smiles

    CCO

    Description

    Ethanol

  2. Smiles

    CCO

    Description

    PBr₃ converts OH to good leaving group

  3. Smiles

    CCBr

    Description

    Br⁻ displaces (inversion at 2° centers)

Stereochemistry

Inversion (SN2 mechanism)

Tips

  1. OH is poor leaving group - PBr₃ activates it

  2. Works for 1° and 2° alcohols

  3. Alternative: SOCl₂ for chlorides

Related Reactions

  • sn2-bromide-hydroxide

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Reactions

Related Content

Reagents, conditions, stereochemistry and mechanism.

SN2 with Hydroxide

SN2 with Hydroxide (SN2 Substitution). Starts from Bromoethane with NaOH, KOH. Conditions: Polar aprotic solvent in DMSO, DMF, or acetone. Stereochemistry: Inversion of configuration (Walden inversion). Mechanism in 3 steps.

Substitution

SN2 with Cyanide

SN2 with Cyanide (SN2 Substitution). Starts from Iodoethane with NaCN, KCN. Conditions: Polar aprotic solvent in DMSO or DMF. Stereochemistry: Inversion of configuration. Mechanism in 3 steps.

Substitution

SN1 Solvolysis

SN1 Solvolysis (SN1 Substitution). Starts from Tertiary bromide with H₂O. Conditions: Polar protic solvent, heat in Water or aqueous ethanol. Stereochemistry: Loss of stereocontrol (planar carbocation attacked from either face → racemization if chiral center)...

Substitution

SN2 with Tosylate Leaving Group

SN2 with Tosylate Leaving Group (SN2 Substitution). Starts from Ethyl tosylate with NaN₃. Conditions: Polar aprotic solvent. Mechanism in 2 steps.

Substitution

SN2 with Azide

SN2 with Azide (SN2 Substitution). Starts from Alkyl bromide substrate with NaN₃. Conditions: Polar aprotic solvent. Mechanism in 2 steps.

Substitution

E2 Elimination

E2 Elimination (E2 Elimination). Starts from 2-Bromobutane with KOtBu, NaOEt, NaOH (conc.). Conditions: Strong base, heat in t-BuOH or EtOH. Stereochemistry: Anti-periplanar geometry required. E/Z depends on which H is removed.. Mechanism in 3 steps.

Elimination

Study guides

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