3,5-Dinitrobenzoic acid

3,5-Dinitrobenzoic acid is an organic chemical that is an important corrosion inhibitor and is also used in photography. This aromatic compound is used by chemists to identify alcohol components in esters and in the fluorometric analysis of creatinine.

3,5-Dinitrobenzoic acid
Skeletal formula
Ball-and-stick model
Names
Preferred IUPAC name
3,5-Dinitrobenzoic acid
Identifiers
3D model (JSmol)
1914286
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.002.501
EC Number
  • 202-751-1
UNII
Properties
C7H4O6N2
Molar mass 212.118 g/mol
Appearance Yellow or colourless crystals
Melting point 205 to 207 °C (401 to 405 °F; 478 to 480 K)
Acidity (pKa) 2.82
Hazards
GHS pictograms
GHS Signal word Warning
H302, H315, H319, H335, H413
P261, P264, P270, P271, P273, P280, P301+312, P302+352, P304+340, P305+351+338, P312, P321, P330, P332+313, P337+313, P362, P403+233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Synthesis

3,5-dinitrobenzoic acid is obtained from benzoic acid by the nitration reaction with nitric acid in the presence of concentrated sulfuric acid.[1][2]

The nitration can also be started with 3-nitrobenzoic acid, which leads to yields of approximately 98 %.[3]

Properties

3,5-Dinitrobenzoic acid is an odorless, yellowish solid. Due to the mesomeric effect of the two nitro groups, it is more acidic (pKa = 2.82) than benzoic acid (pKa = 4.20) and 3-nitrobenzoic acid (pKa = 3.47).

Uses

3,5-Dinitrobenzoic acid finds use in the identification of various organic substances, especially alcohols, by derivatization. For such an analysis, the substance to be analyzed is reacted with 3,5-dinitrobenzoic acid in the presence of sulfuric acid in order to form a derivate. By doing so, many substances that are liquid or have a low melting point are converted to easily crystallized derivates with sharp melting points. For instance, alcohols can be identified by the melting point of their esters with 3,5-dinitrobenzoic acid. This method is also applicable to a large number of amines.

Identification of isopropanol as a derivate of 3,5-dinitrobenzoic acid:
3,5-dinitrobenzoic acid-2-propylester (mp.: 123 °C[4]).

Compared to 4-nitrobenzoic acid, another acid that is used similarly, derivates of 3,5-dinitrobenzoic acid have higher melting points, so that it is preferred when the 4-nitrobenzoic acid derivate has a melting point too low to be accurately identified.[4]

For more sensitive compounds, the reaction is carried out using the acid chloride, 3,5-dinitrobenzoyl chloride. This allows for example the identification of amino acids.[1]

References
  1. Saunders, B. C.; Stacey, G. J.; Wilding, I. G. E. (1942). "The Preparation of 3:5-Dinitrobenzoic Acid and 3:5-Dinitrobenzoyl Chloride – Observations on the Acylation of Amino-acids by means of 3:5-Dinitrobenzoyl Chloride and certain other Acid Chlorides". Biochem. J. 36 (3–4): 368–375. doi:10.1042/bj0360368. PMC 1265703. PMID 16747534.
  2. R. Q. Brewster; Bill Williams; Ross Phillips (1942). "3,5-Dinitrobenzoic Acid". Organic Syntheses. 22: 48. doi:10.15227/orgsyn.022.0048.
  3. Lebedev, B. A.; Dolmatov, V. Yu.; Zubarev, P. S.; Latynov, N. V.; Aleksandrov, M. M.; Ponamareva, R. I (1988). "Preparation of 3,5-dinitrobenzoic acid from meta-nitrobenzoic acid". Pharmaceutical Chemistry Journal. 22 (5): 399–401. doi:10.1007/BF00769656. S2CID 34335456..
  4. CRC Handbook of Tables for Organic Compound Identification, Third Edition, 1984, ISBN 0-8493-0303-6.

Literature


This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.