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Esterification of ethylene glycol with α-bromoisobutyryl bromide; ethylene bis(2-bromoisobutyrate)

SyntheticPage 693
DOI: 10.1039/SP693
Submitted Sep 03, 2013, published Sep 06, 2013
Christopher Waldron (c.s.waldron@warwick.ac.uk)
A contribution from Dave Haddleton Group, Warwick University


			Reaction Scheme: <img src="/images/empty.gif" alt="" />Esterification of <span id="csm1378465970186" class="csm-chemical-name" title="ethylene glycol">ethylene glycol</span> with&nbsp;<span id="csm1378466024900" class="csm-chemical-name" title="&alpha;-bromoisobutyryl bromide">&alpha;-bromoisobutyryl bromide</span><img src="/images/empty.gif" alt="" />

Chemicals Used

ethylene glycol
α-Bromoisobutyryl bromide
triethyl amine (TEA)
tetrahydrofuran (THF)
ethyl acetate
hexane
dichloromethane

Procedure

Ethylene glycol (1.80 mL, 32.4 mmol) and an excess of triethylamine (9.90 mL, 71.3 mmol) were added into a 500 mL round bottom flask with a stirrer bar and flushed with nitrogen for 15 minutes on an ice bath. Anhydrous THF (150 mL) was added into the flask via an airtight syringe, and allowed to cool to 0 °C. Under a nitrogen atmosphere, α-bromoisobutyryl bromide (8.40 mL, 68.1 mmol) was added slowly via a dropping funnel. The reaction mixture was filtered in order to remove the triethylammonium bromide salt formed, and the solution was concentrated by rotary evaporation. The resulting yellow/brown solution was then stirred with 0.10 M aqueous sodium carbonate to hydrolyze any remaining 2-bromoisobutyryl bromide. The crude product was then extracted with dichloromethane (3 × 50 mL) using a separating funnel and the combined dichloromethane extracts were dried with anhydrous magnesium sulfate and then filtered. The solvent was removed via rotary evaporation, yielding yellow crystals upon cooling. The product was purified by flash column chromatography with 3:1 ethyl acetate:hexane to give white crystals (8.2 g, 70.3%)

Author's Comments

  • Care must be taken during the addition of the α-bromoisobutyryl bromide as the reaction can exotherm quite strongly, hence the need for an ice bath
  • A small amount of the monofunctionalised product is usually formed, even with an excess of the acid bromide.This is easily removed during the purification procedure
  • This is a highly scaleable method and we have been able to synthesise ~100g in one procedure
  • We have found that the crude product can also be purified via repeated re-crystallisation from methanol, which may be an easier option when carrying out this reaction on a larger scale

Data

1H NMR (400Hz, CDCl3): δ (ppm) 4.44 (t, 4H), 1.94 (s, 12H).

Lead Reference

Boyer, A. Atme, C. Waldron, A. Anastasaki, P. Wilson, P. B. Zetterlund, D. Haddleton and M. R. Whittaker, Polym. Chem., 2013, 4, 106-112 http://dx.doi.org/10.1039/c2py20560b

Supplementary Information

Interactive 1HNMR Spectrum
1H NMR Spectrum (ethylene bis(2-bromoisobutyrate).jcamp)

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Get structure file (.cdx, .sk2, .mol)

Keywords: esters

Post new comment
  • Guest Jyoti SharmaMar 5 2019 12:59AMinert atm

    Why are you doing the reaction in the inert atmosphere?

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