Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 3, pp. 511−512. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © S.A. Malin, A.S. Malin, B.M. Laskin, 2008, published in Khimicheskaya Promyshlennost’, 2007, Vol. 84, No. 8, pp. 379−381.
TECHNOLOGY OF ORGANIC
AND INORGANIC CHEMISTRY
Synthesis of -Bromoisovaleric Acid
in the Poliphosphoric Acid Medium
S. A. Malin, A. S. Malin, and B. M. Laskin
Russian Scientiﬁ c Center “Applied Chemistry,” St. Petersburg, Russia
Received March 19, 2007
Abstract—Bromination of isovaleric acid with bromine in the polyphosphoric acid mediumis was studied,
regularities of the process including inﬂ uence of the polyphosphoric acid composition were revealed, the process was
shown technologically attractive for the organization of industrial manufacturing of α-bromoisovaleric acid.
As is known, α-bromoisovaleric acid is commonly
obtained by the method of Gell–Folgard Zelinskii by
which consists of bromination of isovaleric acid with
elemental bromine in the presence of various catalysts
such as red phosphorus or phosphorus halides, acyl
halides, in part, isovaleroyl halides, thionyl chloride and
mineral acids [1–5]. These methods are disadvantageous
because of high consuming of bromine and catalyst,
high temperature of the process and due to formation of
isovaleric acid chlorine derivatives as side products.
An attractive method is bromination of isovaleric
acid with bromine in the medium of polyphosphoric
acid. This method has been considered in [6, 7], but the
process features have not been published. Preparation
of α-bromoisovaleric acid by his method in our opinion
seems acceptable in respect of technology.
We explored bromination of isovaleric acid in the
medium of polyphosphoric acid in details. We studied
effects of reagents ratio, their total concentration in
polyphosphoric acid, thermal and timing parameters. We
Table 1. Bromination of isovaleric acid in the medium of polyphosphoric acid
found that bromination proceeds smoothly in 30–60%
solutions of the reagents in polyphosphoric acid and
affords α-bromoisovaleric acid in the yield up to 92–94%.
For example, at the reagents content in polyphosphoric
acid in the range 25–45% and isovaleric acid–bromine
ratio 1 : 1.09 the bromination proceeds at 40–70°C in
4–5 h with 90–94% yield. Therewith, duration of the
reaction completing increases owing probably to diffusion
character of the process. The results obtained are listed
in Table 1.
Yield of bromoisovaleric acid is high enough and
Study of isovaleric acid bromination in polyphos-
phoric acid of different compositions showed that at
the phosphoric anhydride content in polyphosphoric
acid from 20 to 40 wt% the bromination proceeds
smoothly resulting in up to 92% yield of α-bromo-
isovaleric acid. Further increase in phosphoric
anhydride content to 55% affects negatively the
bromination process because the system becomes