3,5-Dinitrosalicylic acid
- DNS
- DNSA
- 2-hydroxy- 3 ,5- dinitrobenzoic acid
- 609-99-4
- 138659-74-2 (monohydrate)
Light yellow crystals with a faint odor
Fixed
1.70 to 1.72 g · cm -3 ( monohydrate)
170-174 ° C
- PKS1 = 2.96
- PKa2 = 7.61
- Soluble in water: 13.55 g · l -1 ( 21 ° C)
- Slightly soluble in methanol, 1 -octanol
Attention
860 mg · kg -1 ( LD50, rat, oral)
Template: Infobox chemical / molecular formula search available
3,5-dinitrosalicylic acid (DNS ) is a phenolic acid which gives with reducing sugars or other reducing molecules, a typical color reaction.
Properties
3,5-dinitrosalicylic acid is a carboxylic acid having a pK value of 2.96 for the carboxy group and 7.61 for the phenolic OH group. The octanol - water partition coefficient (log Kow ) is 1.71. From monohydrate you can isolate two different crystal forms, their densities with 1.702 g/cm3 ( crystallized from ethanol ) and 1.719 g/cm3 ( crystallized from water) also differ.
Use
With reducing sugars 3,5-dinitrosalicylic acid is reduced to 3- amino-5- nitrosalicylic acid, which strongly absorbs light at 540 nm. In this reaction, the solution color from orange-yellow to red beats by.
The colorimetric reaction was first introduced for the determination of reducing substances in the urine and has since been used widely, for example for quantification of carbohydrates into the blood. Mainly used to the detection reaction at the α -amylase assay. The method combines the oxidation of a carbonyl compound with the reduction of a nitro group in the 3,5- dinitrosalicylic acid under alkaline conditions. Uses an alkaline reaction solution with 2% and 2% Na2CO3 DNS. Other urine constituents do not interfere.
Enzymatic methods are, however, now usually preferred to determine the 3,5-dinitrosalicylic acid, because they are specific.
Compounds
The sodium salt of 3,5-dinitrosalicylic acid crystallizes as a monohydrate and is listed under CAS number 46506-88-1.