Ipatiev synthesis

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The Ipatiev synthesis is a name reaction in organic chemistry . It was named after Vladimir Nikolayevich Ipatyev, a Russian chemist . It is also called technical isooctane synthesis . It is a rare case of an addition reaction of a carbenium ion to alkenes without any polymerization occurring.

Overview reaction

In the Ipatiev synthesis, isobutene and isobutane are added to obtain isooctane .

Overview reaction of the Ipatiev synthesis

For the reaction to take place at all, a high pressure and a high temperature must be set. The synthesis starts slowly at 325 ° C and proceeds best at 380-400 ° C. The reaction is not possible without the pressure increase.

mechanism

Reinhard Brückner expressed the mechanism of the Ipatjew synthesis as follows:

Mechanism of the synthesis of Ipatiev

First, the isobutene (1) is catalytically protolyzed with the aid of an acid [here: hydrofluoric acid (HF)] and a carbenium ion 2 is formed with elimination of a fluoride anion . Another isobutene molecule is then added to this . The intermediate product is another carbenium ion with eight carbon atoms 3 . This then deprotonates an isobutane molecule (4) and thus becomes isooctane (5) . The deprotonated isobutane then forms the carbenium ion 2 again . This means that the reaction can continue until all of the isobutane has been used up.

Examination of the product

Investigations of the product by fractional distillation have shown that the first fraction began to boil at 24 ° C. This fraction contained 50% methane hydrocarbons . In the following fraction mainly naphthenes and low hydrogen hydrocarbons were found. Only in the fraction boiling at 280 ° C. was there a 21% thick oil which did not contain any aromatics. This petroleum-like substance is isooctane. Further implementation with aluminum hydroxide as a catalyst gave a higher yield (approx. 44.7%) of isooctane.

criticism

The Ipatiev synthesis is a technical process. Nevertheless, the atom economy of the Ipatiev synthesis is so bad, because of the formation of stoichiometric amounts of several waste materials , that it is only rarely carried out.

Individual evidence

  1. ↑ a b c Reinhard Brückner: reaction mechanisms . Elsevier Spektrum Verlag, Munich 2004, ISBN 3-8274-1579-9 , pp. 155 .
  2. ↑ Louis F. Fieser, Mary Fieser: Textbook of organic chemistry . Chemie, Weinheim 1957, p. 68 .
  3. ^ A b c d Leo Gurwitsch : Scientific principles of petroleum processing . Springer Verlag, Heidelberg 1924, ISBN 978-3-642-47512-2 , p. 109 .