Hydrochloric Acid → Beta-Carotene

HRID 28272

Reaction equation

HRID 28272 reaction equation
[CH3:1][C:2]1[CH2:7][CH2:6][CH2:5][C:4]([CH3:9])([CH3:8])[C:3]=1/[CH:10]=[CH:11]/[C:12](/[CH3:21])=[CH:13]/[CH:14]=[CH:15]/[C:16](/[CH3:20])=[CH:17]/[CH:18]=O.Cl>O1CCCC1>[CH3:1][C:2]1[CH2:7][CH2:6][CH2:5][C:4]([CH3:9])([CH3:8])[C:3]=1/[CH:10]=[CH:11]/[C:12](/[CH3:21])=[CH:13]/[CH:14]=[CH:15]/[C:16](/[CH3:20])=[CH:17]/[CH:18]=[CH:18]/[CH:17]=[C:16](\[CH3:20])/[CH:15]=[CH:14]/[CH:13]=[C:12](\[CH3:21])/[CH:11]=[CH:10]/[C:3]1[C:4]([CH3:9])([CH3:8])[CH2:5][CH2:6][CH2:7][C:2]=1[CH3:1]

Participants

4

Reactant 2

HCID 313Hydrochloric AcidHCID 638015Retinal

Product 1

HCID 5280489Beta-CaroteneYield 65%

Reagents, catalysts & solvents 1

HCID 8028TetrahydrofuranSolvent

Procedure

Zinc dust (654 mg, 10.0 mmol) was slurred in 20 ml dry tetrahydrofuran under an inert atmosphere (nitrogen or argon), and a solution of titanium tetrachloride (0.55 ml, 5.0 mmol) in 3 ml dry benzene was rapidly added. The resulting solution was refluxed overnight to form active Ti(II) reagent, and a solution of retinal (710 mg, 2.5 mmol) in 5 ml dry tetrahydrofuran was added. After refluxing for a further two hours, the solution was cooled to room temperature, poured into 50 ml 2 N aqueous hydrochloric acid, and extracted with ether. The ether extracts were combined, washed with saturated aqueous sodium chloride solution, dried over magnesium sulfate, and concentrated by solvent removal at the rotary evaporator. The residue was purfied by chromatography on a silica gel column. Elution with hexane gave 430 mg (65% yield) of beta-carotene which crystallized in the flask. The beta-carotene was identified by tlc comparison with an authentic sample, and by melting point comparison of a recrystallized sample; mp 180°-182°.

Workup

  1. temperatureAfter refluxing for a further two hours
  2. extractionextracted with ether
  3. washwashed with saturated aqueous sodium chloride solution
  4. dry with materialdried over magnesium sulfate
  5. concentrationconcentrated by solvent removal at the rotary evaporator
  6. washElution with hexane

Sources & evidence

ORD record
ord-d7a85694fef74b76873e3c2ddf31d020
Source dataset
uspto-grants-1980_09
Patent number
US04225734

Linked notes

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