Propiolic acid

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Structural formula
Structural formula of propiolic acid
General
Surname Propiolic acid
other names
  • Acetylenecarboxylic acid
  • Propynoic acid ( IUPAC )
  • Propargylic acid
Molecular formula C 3 H 2 O 2
External identifiers / databases
CAS number 471-25-0
EC number 207-437-8
ECHA InfoCard 100.006.763
PubChem 10110
ChemSpider 9706
Wikidata Q257590
properties
Molar mass 70.05 g mol −1
Physical state

liquid

density

1.1325 g cm −3

Melting point

18 ° C

boiling point
  • 102 ° C (200 mmHg)
  • 153–157 ° C (1013 hPa) (decomposition)
pK s value

1.94 (25 ° C)

Refractive index

1.4315-1.4335

safety instructions
GHS labeling of hazardous substances
02 - Highly / extremely flammable 06 - Toxic or very toxic 05 - Corrosive

danger

H and P phrases H: 226-301-314-335
P: 280-301 + 330 + 331-305 + 351 + 338-304 + 340
Toxicological data

100 mg kg −1 ( LD 50 ,  rat ,  oral )

Thermodynamic properties
ΔH f 0

−193.2 kJ mol −1

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Propiolic acid , also called acetylenic acid or propynic acid, is a liquid unsaturated organic acid that smells like acetic acid. Metal salts (e.g. the silver salt) of the compound are explosive. The salts are commonly called propiolates.

Extraction and presentation

The synthesis can start from maleic acid , in which case 2,3- dibromosuccinic acid is initially obtained by bromination . A double dehydrohalogenation in a basic medium leads to acetylenedicarboxylic acid , the decarboxylation of which gives propiolic acid.

Synthesis of propiolic acid

Propiolic acid can be produced by anodic oxidation of propargylic alcohol and is therefore also called propargylic acid.

properties

Physical Properties

Anhydrous propiolic acid melts at 18 ° C. The phase diagram with water shows two stoichiometric hydrates. These are a 1/3 hydrate with a melting point of 10 ° C and a monohydrate with a melting point of −0.3 ° C. Between anhydrate and 1/3 hydrate, and between 1/3 hydrate and monohydrate, eutectic mixtures are formed at 96% by mass of propiolic acid with a melt at 7 ° C and at 79% by mass of propiolic acid with a melt at −0.5 ° C observed. The connection is very hygroscopic. A low water content causes a significant decrease in the melting point. Propiolic acid is a relatively strong acid . The pK s value in water at 25 ° C 1.94 and is similar to hydrogen sulfate (pK s 1.92) or phosphoric acid (pK s 2.13).

Chemical properties

The copper (II) propiolate can be isolated by reacting with basic copper (II) hydroxide. This is only stable for about 24 hours and decarboxylates to black, polymeric copper (II) acetylide . In a strongly basic medium, a redox reaction takes place with dimerization to the copper (I) salt of diacetylenedicarboxylic acid.

use

Propiolic acid and its esters serve as starting materials for organic syntheses.

Individual evidence

  1. ↑ a b c Entry on propiolic acid at ChemBlink , accessed on February 25, 2011.
  2. ↑ a b c d e f F. Straus, W. Heyn, E. Schwemer: For the knowledge of propiolic acid in Chem. Ber. 63 (1930), pp. 1086-1092; doi: 10.1002 / cber.19300630513 .
  3. ↑ a b c d Acetylenecarboxylic acid data sheet (PDF) from Merck , accessed on April 22, 2011.
  4. ↑ a b C. Laurence, J. Guillemé, B. Kirschleger: Ionization constants of 3-substituted propiolic acids in water in J. Chem. Soc., Perkin Trans. 2, 1981, pp. 1341-1343, doi : 10.1039 / P29810001341 .
  5. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-23.
  6. ↑ W. Lossen: On the knowledge of the doubly brominated succinic acids in Justus Liebig's Annalen der Chemie 272 (1893), pp. 127-139, doi : 10.1002 / jlac.18932720202 .
  7. ↑ a b entry on propiolic acid. In: Römpp Online . Georg Thieme Verlag, accessed on June 14, 2014.

literature

  • Merck Index. 11th edition. P. 7833.
  • Yasuo Iwanami, Seiko Isoyama, Yoshihisa Kenjo: The reaction of acetylenic acid with amines. XIII. Substituted 2-oxo-3-ethoxycarbonylmethylene-3,4-dihydro-2H-1,4-benzoxazines. In: Bulletin of the Chemical Society of Japan. 37, 1964, pp. 1745-1747, doi : 10.1246 / bcsj.37.1745 .