Study on the preparation method and application of 5,5-dimercapto-2,2-dinitrobenzoic acid_Kain Industrial Additive

Background and overview^[1]

It is also called DTNB (5,5′-Dithiobis-(2-nitrobenzoic acid)), which is the abbreviation of 5,5-dithiobis-2,2-dinitrobenzoic acid. DTNB is widely used in Analytical reagents in the field of biochemistry,

Preparation^[1]

A total synthesis method of 5,5-dimercapto-2,2-dinitrobenzoic acid, including:

Nitrification step: Add 24.3 mL (0.2 mol) of m-bromotoluene to a 250 mL three-necked flask equipped with a stirrer, condenser tube and thermometer. Add 28 mL of mixed acid dropwise, and control the dropping speed so that the temperature of the solution is at 45-45. 55°C, complete the dropwise addition, keep the reaction at 50°C for 2 hours, discard the acid layer, extract the organic phase with toluene, combine the extracts, dry, and rotary evaporate to obtain 29.1g (0.135mol) of a light yellow needle-shaped product, which is 2-nitrate methyl-5-bromotoluene, the yield is 67.4%, the melting point is 55-56°C;

Oxidation step: Add 21.6g (0.1mol) of 2-nitro-5-bromotoluene obtained in the nitration step to 100mL of water, stir and heat to 50°C, add 800g of 5wt% potassium permanganate (0.253mol) solution, Insulate the reaction, filter to remove the precipitate, adjust the filtrate to pH<1 with 1+1 hydrochloric acid, collect the precipitate, and dry to obtain 19.6g (0.0797mol) of 2-nitro-5-bromo-benzoic acid, with a yield of 79.7%. Melting point is 138-140℃;

Sulfidation step: Dissolve 12.3g (0.05mol) of 2-nitro-5-bromo-benzoic acid obtained in the oxidation step with 50mL of water, adjust the pH>3.5, stir and heat to 50°C, and add 65g of 6wt in batches % sodium sulfide (0.05mol) aqueous solution, incubate for 2 hours, adjust pH<1 with 1+1 hydrochloric acid, collect the precipitates, and dry to obtain 7.16g (0.0181mol) 5,5-dimercapto-2,2- Dinitrobenzoic acid, yield 72.3%;

Recrystallization step: Take 5.95g (0.0150mol) of 5,5-dimercapto-2,2-dinitrobenzoic acid obtained in the sulfidation step, add glacial acetic acid to recrystallize, and obtain 5.42g (0.0137mol) after purification 5,5-dimercapto-2,2-dinitrobenzoic acid, the yield is 91.0%, the melting point is 236-237°C.

Apply^[2-3]

CN201510097778.3 discloses a cervical cancer urine detection kit, which includes a container 1 and a container 2, wherein the container 1 contains 2 ml of 5,5-dimercapto-2,2-dinitrobenzoic acid solution, and the container 2 contains 2 ml of phosphotungstic acid solution. The invention also discloses a method of using the kit. Take 1 ml of the subject’s morning urine, drop it into a container containing DTNB solution, let it stand for 2-5 minutes, then add it to a container containing phosphotungstic acid solution, and let it stand. Leave for 2-5 minutes and observe whether there is a color change in the solution. Through the color reaction, the kit can conveniently and quickly determine whether the subject has cervical cancer.

CN201910277653.7 reports a mercury-free detection reagent for urine thiol compounds and its preparation method and application. The reagent includes a buffer and 5,5-dimercapto-2,2-dinitrobenzoic acid and EDTA dispersed in the buffer. The preparation method is to measure and mix the above components. It can be used to prepare a kit for the preparation of mercury-free detection reagents for urine thiol compounds. The technical solution provided by the invention uses 5,5-dimercapto-2,2-dinitrobenzoic acid as a thiol chromogen to conduct qualitative and quantitative analysis of thiol groups in urine, and successfully improves it into urine that can be used as a product Detection reagent. The components of the detection reagent are environmentally friendly. It no longer contains heavy metal ions such as mercury. It will not cause environmental pollution after use. It also no longer contains corrosive substances such as trichloroacetic acid, which improves the safety of use and greatly speeds up the detection rate. , shortened from at least 15 minutes to less than 5 minutes; in summary, the detection reagents provided are highly operable and easy to promote and use, so the market prospects are broad.

Main reference materials

[1] [Invented in China] CN201711494442.6 A total synthesis method of DTNB

[2] CN201510097778.3 Cervical cancer urine detection kit

[3] CN201910277653.7 A mercury-free detection reagent for urine thiol compounds and its preparation method and application