Benzene → 2-Phenylisobutyric acid

HRID 1105929Notes

Reaction equation

HRID 1105929 reaction equation
Br[C:2]([CH3:7])([CH3:6])[C:3]([OH:5])=[O:4].[Al+3].[Cl-].[Cl-].[Cl-].Cl.O.[CH:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1>>[CH3:6][C:2]([CH3:7])([C:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1)[C:3]([OH:5])=[O:4]

Participants

5

Reactant 4

HCID 241BenzeneHCID 749242-Bromo-2-methylpropanoic acidHCID 6451240Aluminum(III) ChlorideHCID 21885828Hydrate;hydrochloride

Product 1

HCID 132222-Phenylisobutyric acid

Conditions

Temperature
5 °C

Procedure

Molten alpha-bromoisobutyric acid, 328 g, 2 moles, was added to a 5-L flask equipped with a reflux condenser and large magnetic stirrer. Anhydrous benzene 2000 mL, was added to the flask, followed by fresh anhydrous AlCl3, 900 g, 6.75 moles, in small portions. The solution was then slowly heated to the reflux temperature and at this time the exit of the reflux condenser was connected to a flowing-water HBr trap. The mixture was heated a total of 24 hours without interruption. The reaction mixture was then cooled to ca. 5° C. and treated with 2 L of 50/50 (by volume) conc. HCl/H2O to decompose the catalyst complex. The benzene layer was then separated, washed once with ice-cold H2O (1200 mL) and twice with dilute aqueous sodium hydroxide. The aqueous sodium hydroxide extracts were combined, heated to 80° C. to drive out any physically trapped benzene and decolorized with activated charcoal. After filtration through diatomaceous earth filter aid ("Celite") the aqueous basic filtrate was neutralized slowly with conc. HCl. The precipitated acid was filtered, washed with a minimum amount of ice-cold water, and dried in a vacuum oven at 25°-30° C. The crude yield was 209 g (65%), and the melting point at this stage was 75.5°-77° C. The crude acid was recrystallized from n-heptane (450 mL for ca. 200 g acid). The final yield was 180 g of mp=76°-78°.

Workup

  1. customequipped with a reflux condenser and large magnetic stirrer
  2. temperatureThe solution was then slowly heated to the reflux temperature and at this time the exit of the reflux condenser
  3. temperatureThe mixture was heated a total of 24 hours without interruption
  4. customThe benzene layer was then separated
  5. washwashed once with ice-cold H2O (1200 mL) and twice with dilute aqueous sodium hydroxide
  6. temperatureheated to 80° C.
  7. filtrationAfter filtration through diatomaceous earth
  8. filtrationfilter aid ("Celite") the aqueous basic filtrate
  9. filtrationThe precipitated acid was filtered
  10. washwashed with a minimum amount of ice-cold water
  11. customdried in a vacuum oven at 25°-30° C
  12. customwas 75.5°-77° C
  13. customThe crude acid was recrystallized from n-heptane (450 mL for ca. 200 g acid)

Sources & evidence

ORD record
ord-f5ddfb3fcac04956917944f196fa3861
Source dataset
uspto-grants-1982_01
Patent number
US04310655

Reaction notes

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