von Braun reaction

The von Braun reaction is an organic reaction in which a tertiary amine reacts with cyanogen bromide to an organocyanamide.[1] An example is the reaction of N,N-dimethyl-1-naphthylamine:[2]

von Braun reaction
Named after Julius von Braun
Reaction type Substitution reaction
Reaction
tertiary amine
+
cyanogen bromide
↓
organocyanamide

von Braun reaction

These days, most chemist have replaced cyanogen bromide reagent with chloroethyl chloroformate reagent instead. It appears as though Olofson et al. was the first chemist to have reported this.[3]

Reaction mechanism

The reaction mechanism consists of two nucleophilic substitutions: the amine is the first nucleophile displacing the bromine atom which then acts as the second nucleophile.[4][5] In following the mechanism is described using trimethylamine as example:[6]

First, the trimethylamine reacts with the cyanogen bromide to form a quaternary ammonium salt, which in the next step reacts by splitting off bromomethane to give the dimethylcyanamide. This is a second-order nucleophilic substitution (SN2).

See also

References
  1. J. von Braun; K. Heider & E. Müller (1918). "Bromalkylierte aromatische Amine. II. Mitteilung". Chem. Ber. 51 (1): 273–282. doi:10.1002/cber.19180510132.
  2. Homer W. J. Cressman (1947). "N-Methyl-1-Naphthylcyanamide". Org. Synth. 27: 56. doi:10.15227/orgsyn.027.0056.
  3. J. Org. Chem. 1984, 49, 11, 2081–2082 Publication Date:June 1, 1984 https://doi.org/10.1021/jo00185a072
  4. March, Jerry (1985), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 3rd edition, New York: Wiley, ISBN 9780471854722, OCLC 642506595
  5. Howard A. Hageman (1953). "The Von Braun Cyanogen Bromide Reaction". Organic Reactions. 7 (4): 198–262. doi:10.1002/0471264180.or007.04. ISBN 0471264180.
  6. Jie Jack Li (2014), Name reactions: A collection of detailed mechanisms and synthetic applications (in German) (5th ed.), Cham: Springer, p. 619, doi:10.1007/978-3-319-03979-4, ISBN 978-3-319-03979-4, S2CID 93616494
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