Cooking acids

from Wikipedia, the free encyclopedia
The simplest cooking acid, pivalic acid

With Koch acids are tertiary saturated monocarboxylic acids designated; the simplest representative is pivalic acid ( 2,2-dimethylpropanoic acid ). The name was derived from the production by Koch's carboxylic acid synthesis ( formylation or carbonylation ) from olefins , carbon monoxide and water. Koch acids are much less reactive than primary or secondary carboxylic acids because the carboxylic acid carbon atom is sterically hindered . This makes the esterification more difficult , but on the other hand results in esters which are thermally stable and largely resistant to oxidation and which, under normal reaction conditions, can no longer be split into carboxylic acid and alcohol by hydrolysis . The annual production of the cooking acids is around 150,000  t .

presentation

Starting from a branched alkene such as isobutene ( 2-methylpropene ), this is first reacted with carbon monoxide under a pressure of 5 · 10 5 to 10 7 Pa and at temperatures between 0 ° C and 50 ° C. A mixture of phosphoric acid ( H 3 PO 4 ) and boron trifluoride ( BF 3 ) is used as the acidic catalyst . After the hydrolysis , the carboxylic acid is formed and the proton is taken up again by the acidic catalyst.

Scheme of the Koch reaction

The reaction conditions of pressure and temperature essentially determine which products are formed.

Manufacturer of cooking acids

Various corporations such as Shell , Exxon , DuPont and Kuhlmann produce cooking acids and name the manufactured products according to their own scheme:

  • Shell calls its products Versatic acids and names them after the total number of C atoms in the molecule ( Versatic 5 is 2,2-dimethylpropionic acid , Versatic 6 is 2,2-dimethylbutyric acid , etc.).
  • Exxon makes what are known as neo acids .
  • Kuhlmann calls the in-house cooking acids CeKanoic acids .

Representative

The Koch acids only differ in the length of the carbon chain and thus represent a homologous series :

Properties of the simplest cooking acids
Surname Pivalic acid 2,2-dimethylbutyric acid 2,2-dimethylvaleric acid
Molecular formula C 5 H 10 O 2 C 6 H 12 O 2 C 7 H 14 O 2
structure Pivalic Acid Structural Formulas V.1.svg 2,2-Dimethyl butanoic acid.png 2,2-Dimethyl pentanoic acid.png
IUPAC name 2,2-dimethylpropanoic acid 2,2-dimethylbutanoic acid 2,2-dimethylpentanoic acid
Melting point 33-35 ° C −15 ... −13 ° C
boiling point 163-164 ° C 186-187 ° C 199 ° C

use

The cooking acids themselves are used in resins and paints, as peroxide catalysts and for the extraction of metal salts. Due to their high stability, esters of the Koch acids can be used in a variety of ways: They serve as components for semi or fully synthetic oils and lubricants , vinyl esters as internal plasticizers , and glycidyl esters are processed into epoxy resins . Metal salts of cooking acids act as siccatives and accelerate the drying of technical products such as paints and varnishes. Textile auxiliaries and heat and light stabilizers for PVC are also made from cooking acids.

Individual evidence

  1. ↑ Fritz Ullmann, Wilhelm Foerst (Ed.): Enzyklopädie der technischen Chemie , Vol. 1-19. 3. Edition. Urban & Schwarzenberg, 1970, p. 132.
  2. ↑ a b c J. Arpe: Industrial organic chemistry: important preliminary and intermediate products . Wiley-VCH-Verlag, Weinheim 2007, ISBN 3-527-31540-3 .
  3. ↑ a b c d carboxylic acids . (PDF; 163 kB) Aklimex.de