N-Bromosuccinimide
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| n-Bromosuccinimide | |
|---|---|
  |
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| General | |
| Systematic name | 1-Bromo-2,5-pyrolidinedione |
| Other names | NBS |
| Molecular formula | C4H4BrNO2 |
| SMILES | O=C(CC1)N(Br)C1=O |
| Molar mass | 177.98 g/mol |
| Appearance | White solid |
| CAS number | 128-08-5 |
| Properties | |
| Density and phase | 2.098 g/cm3 (solid) |
| Solubility in water | 1.47 g / 100 mL (25 °C) |
| Solubility | Soluble: Acetone, THF, DMF, DMSO, MeCN |
| Melting point | 175-178 °C (dec) |
| Structure | |
| Crystal structure | ? |
| Dipole moment | ? D |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | Irritant |
| NFPA 704 |
0
2
0
|
| Flash point | None |
| R/S statement | R: ? S: ? |
| RTECS number | ? |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Related halides | N-bromoacetamide, N-chlorosuccinimide, N-iodosuccinimide |
| Related compounds | Succinimide |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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N-Bromosuccinimide or NBS is a chemical reagent which is used in radical substitution and electrophilic addition reactions in organic chemistry. NBS can be considered a convenient source of bromine.
Contents |
[edit] Reactions of N-Bromosuccinimide
[edit] Addition to alkenes
NBS will react with alkenes 1 in aqueous solvents to give bromohydrins 2. The preferred conditions are the portionwise addition of NBS to a solution of the alkene in 50% aqueous DMSO, DME, THF, or tert-butanol at 0°C. Formation of a bromonium ion and immediate attack by water gives strong Markovnikov addition and anti stereochemical selectivities.
Side reactions include the formation of α-bromo-ketones and dibromo compounds. These can be minimized by the use of freshly recrystallized NBS.
With the addition of nucleophiles, instead of water, various bifunctional alkanes can be synthesized.
[edit] Allylic and benzylic bromination
Standard conditions for using NBS in allylic and/or benzylic bromination involves refluxing a solution of NBS in anhydrous CCl4 with a radical initiator, usually azo-bis-isobutyronitrile (AIBN), benzoyl peroxide, irradiation, or both to effect radical initiation. This is also called the Wohl-Ziegler reaction.
The carbon tetrachloride must be maintained anhydrous throughout the reaction, as the presence of water may likely hydrolyze the desired product. Barium carbonate is often added to maintain anhydrous and acid-free conditions.
[edit] Bromination of carbonyl derivatives
NBS can α-brominate carbonyl derivatives via either a radical pathway (as above) or via acid-catalysis. For example, hexanoyl chloride 1 can be brominated in the alpha-position by NBS using acid catalysis.
The reaction of enolates, enol ethers, or enol acetates with NBS is the preferred method of α-bromination as it is high-yielding with few side-products.
[edit] Bromination of aromatic derivatives
Electron-rich aromatic compounds, such as phenols, anilines, and various aromatic heterocycles, can be brominated using NBS. Using DMF as the solvent gives high levels of para-selectivity.
[edit] Hofmann rearrangement
NBS, in the presence of a strong base, such as DBU, reacts with primary amides to produce a carbamate via the Hofmann rearrangement.
[edit] Selective oxidation of alcohols
It is uncommon, but possible for NBS to oxidize alcohols. E. J. Corey et al. found that one can selectively oxidize secondary alcohols in the presence of primary alcohols using NBS in aqueous DME.
[edit] Preparation
To a well-stirred ice-water solution of succinimide is added sodium hydroxide and then bromine. The product, NBS, precipitates out and can be collected by filtration. To purify the NBS, it can be recrystallized from water. Crude NBS gives better yield in the Wohl-Ziegler reaction.
[edit] Purification by recrystallization
Impure NBS (slightly yellow-colored) may give unreliable results. NBS can be recrystallized as follows: In an erlermeyer flask, add crude NBS (break up any clumps first) to 90-95 degree water in a ratio of 125 ml water for every 10 g of NBS. Swirl to dissolve, then place the flask in an ice bath until well-chilled. Collect the crystals by vacuum filtration over a bed of ice and dry them in air or under high-vacuum.
[edit] Precautions
Although NBS is easier and safer to handle than bromine, precautions should be taken to avoid inhalation. NBS should be stored in a refrigerator. NBS will decompose over time giving off bromine. Pure NBS is white, but it is often found to be off-white or brown colored by bromine.
In general, reactions involving NBS are exothermic. Therefore, extra precautions should be taken when used on a large scale.
[edit] References
- ^ Hanzlik, R. P. Organic Syntheses, Coll. Vol. 6, p.560 (1988); Vol. 56, p.112 (1977). (Article)
- ^ Beger, J. J. Prakt. Chem. 1991, 333(5), 677-698.
- ^ Haufe, G.; Alvernhe, G.; Laurent, A.; Ernet, T.; Goj, O.; Kröger, S.; Sattler, A. Organic Syntheses, Coll. Vol. 10, p.128 (2004); Vol. 76, p.159 (1999). (Article)
- ^ Djerassi, C.; Chem. Rev. 1948, 43, 271.
- ^ Greenwood, F. L.; Kellert, M. D.; Sedlak, J. Organic Syntheses, Coll. Vol. 4, p.108 (1963); Vol. 38, p.8 (1958). (Article)
- ^ Wohl, A. Ber. 1919, 52, 51.
- ^ Ziegler, K.; et al. Ann. 1942, 551, 30.
- ^ Binkley, R. W.; Goewey, G. S.; Johnston, J; J. Org. Chem. 1984, 49, 992.
- ^ Harpp, D. N.; Bao, L. Q.; Coyle, C.; Gleason, J. G.; Horovitch, S. Organic Syntheses, Coll. Vol. 6, p.190 (1988); Vol. 55, p.27 (1976). (Article)
- ^ Stotter, P. L.; Hill, K. A.; J. Org. Chem. 1973, 38, 2576.
- ^ Lichtenthaler, F. W.; et al. Synthesis 1992, 179.
- ^ Amat, M.; Hadida, S.; Sathyanarayana, S.; Bosch, J. Organic Syntheses, Coll. Vol. 9, p.417 (1998); Vol. 74, p.248 (1997). (Article)
- ^ Gilow, H. W.; Burton, D. E.; J. Org. Chem. 1981, 46, 2221.
- ^ Brown. W. D.; Gouliaev, A. H. Organic Syntheses, Vol. 81, p.98 (2005). (Article)
- ^ Mitchell, R. H.; Lai, Y.-H.; Williams, R. V.; J. Org. Chem. 1979, 44, 4733.
- ^ Keillor, J. W.; Huang, X. Organic Syntheses, Coll. Vol. 10, p.549 (2004); Vol. 78, p.234 (2002). (Article)
- ^ Corey, E. J.; Ishiguro, M. Tetrahedron Lett. 1979, 20, 2745-2748.
