N-Bromosuccinimide

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N-Bromosuccinimide
Skeletal formula of N-bromosuccinimide
Space-filling model of the N-bromosuccinimide molecule
Names
Preferred IUPAC name
1-Bromopyrrolidine-2,5-dione
Other names
N-bromosuccinimide; NBS
Identifiers
3D model (
JSmol
)
113916
ChEBI
ChemSpider
ECHA InfoCard
100.004.435 Edit this at Wikidata
EC Number
  • 204-877-2
26634
UNII
  • InChI=1S/C4H4BrNO2/c5-6-3(7)1-2-4(6)8/h1-2H2 checkY
    Key: PCLIMKBDDGJMGD-UHFFFAOYSA-N checkY
  • InChI=1/C4H4BrNO2/c5-6-3(7)1-2-4(6)8/h1-2H2
    Key: PCLIMKBDDGJMGD-UHFFFAOYAS
  • O=C1N(Br)C(=O)CC1
Properties
C4H4BrNO2
Molar mass 177.985 g·mol−1
Appearance White solid
Density 2.098 g/cm3 (solid)
Melting point 175 to 178 °C (347 to 352 °F; 448 to 451 K)
Boiling point 339 °C (642 °F; 612 K)
14.7 g/L (25 °C)
Solubility in CCl4 Insoluble (25 °C)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Irritant
Safety data sheet (SDS) [1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

N-Bromosuccinimide or NBS is a

chemical reagent used in radical substitution, electrophilic addition, and electrophilic substitution reactions in organic chemistry. NBS can be a convenient source of Br, the bromine
radical.

Preparation

NBS is commercially available. It can also be synthesized in the laboratory. To do so,

precipitates and can be collected by filtration.[1]

Crude NBS gives better yield in the

Wohl-Ziegler reaction. In other cases, impure NBS (slightly yellow in color) may give unreliable results. It can be purified by recrystallization from 90 to 95 °C water (10 g of NBS for 100 mL of water).[2]

Reactions

Addition to alkenes

NBS will react with alkenes 1 in aqueous solvents to give

bromonium ion and immediate attack by water gives strong Markovnikov addition and anti stereochemical selectivities.[4]

Bromohydrin formation

Side reactions include the formation of α-bromoketones and dibromo compounds. These can be minimized by the use of freshly recrystallized NBS.

With the addition of

water, various bifunctional alkanes can be synthesized.[5]

The bromofluorination of cyclohexene

Allylic and benzylic bromination

Standard conditions for using NBS in allylic and/or benzylic

Wohl–Ziegler reaction.[8][9]

Allylic bromination of 2-heptene

The

hydrolyze the desired product.[10] Barium carbonate
is often added to maintain anhydrous and acid-free conditions.

In the above reaction, while a mixture of isomeric allylic bromide products are possible, only one is created due to the greater stability of the 4-position radical over the methyl-centered radical.

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.[11]

succanic acid

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.[12][13]

Bromination of aromatic derivatives

Electron-rich

heterocycles,[14] can be brominated using NBS.[15][16] Using DMF as the solvent gives high levels of para-selectivity.[17]

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.[18]

The Hofmann rearrangement using NBS

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 dimethoxyethane (DME).[19]

The selective oxidation of alcohols using NBS

Oxidative decarboxylation of α-amino acids

NBS electrophilically brominates the amine, which is followed by decarboxylation and release of an imine. Further hydrolysis will yield an aldehyde and ammonia.[20][21] (cf. non-oxidative PLP dependent decarboxylation)

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 using on a large scale.

See also

References

  1. .
  2. .
  3. ^ Hanzlik, R. P. "Selective epoxidation of terminal double bonds". Organic Syntheses; Collected Volumes, vol. 6, p. 560.
  4. .
  5. ^ Haufe, G.; Alvernhe, G.; Laurent, A.; Ernet, T.; Goj, O.; Kröger, S.; Sattler, A. (2004). "Bromofluorination of alkenes". Organic Syntheses; Collected Volumes, vol. 10, p. 128.
  6. PMID 18887958
    .
  7. .
  8. .
  9. .
  10. .
  11. ^ Harpp, D. N.; Bao, L. Q.; Coyle, C.; Gleason, J. G.; Horovitch, S. (1988). "2-Bromohexanoyl chloride". Organic Syntheses; Collected Volumes, vol. 6, p. 190.
  12. .
  13. .
  14. ^ Amat, M.; Hadida, S.; Sathyanarayana, S.; Bosc, J. (1998). "Regioselective synthesis of 3-substituted indoles". Organic Syntheses; Collected Volumes, vol. 9, p. 417.
  15. .
  16. ^ Brown, W. D.; Gouliaev, A. H. (2005). "Synthesis of 5-bromoisoquinoline and 5-bromo-8-nitroisoquinoline". Organic Syntheses. 81: 98.
  17. .
  18. ^ Keillor, J. W.; Huang, X. (2004). "Methyl carbamate formation via modified Hofmann rearrangement reactions". Organic Syntheses; Collected Volumes, vol. 10, p. 549.
  19. .
  20. .
  21. .

External links