2,6-Dichloroquinone 4-chlorimide

Sulfur-containing samples show colored spots when sprayed with 2,6-dibromo-quinone-4-chlorimide Gibbs reagent). For preparation, 2 g of this compound is dissolved in 100 ml of acetic acid or ethanol. Heating to 110°C is necessary to give a reaction. This reagent also creates colored zones when samples contain phenols. For reactions with phenols, only the less-reactive 2,6-dichloroquinone-4-chlorimide can be used under the same conditions. 

Al-Majed [16] described a simple colorimetric method for the determination of (iq-penicillamine in pure form and in pharmaceutical formulations that is based on coupling between (/))-penicillamine and 2,6-dichloroquinone-4-chlorimide (DCQ) in... 

Potter and Shellenberger (1952) developed a spectrophotometric method for detecting insect material (insect phenols) in cereal products. In this method, dihydroxy phenols or 3,4-dihydroxyphenylacetic acid present in insect cuticle is detected by its reaction with 2,6-dichloroquinone-chlorimid, forming a phenol-indophenol dye, which is measured in a spectrophotometer at 580 nm. Because the method is elaborate and time consuming, it has not been pursued. 

Colorless in acid soin, bright-yellow in alkaline soin. uv max (alkaline soin) 390 nm (En 3.7) in acid soin 295 nm (Ea 5.1). Gives a negative 2,6-dichloroquinone chlorimide test. On oxidetion with H. O, in alkaline solution yields [(2-methyl -3,4-dihydroxy -5-pyridyl)methyl]phosphoric aeid-... 

When the developed plate was sprayed with a 2% ethanolic 2,6-dichloroquinone chlorimide solution, then heated for 10 minutes at 100 "C, resprayed with a 5% aqueous borax solution, and heated again for 10 minutes at 100 "C, phosphates gave a bright blue colour and other esters gave no reaction. 

Phenolic antioxidants Benzene Buffered solution, 235 g Na tetraborate, 3.3 g NaOH then 0.1% methanolic dichloroquinone - chlorimide (2 6)... 

Pyridoxal, pyridoxamine and pyridoxine all show the typical reactions of an aromatic phenol unsubstituted fara to the phenolic group. In sufficient concentration they thus show reddish colors on addition of ferric chloride, couple with diazotized sulfanilic acid to yield orange to red-colored products, and with 2,6-dichloroquinone chlorimide to yield blue indophenols. The latter two reactions have been used for the quantitative estimation of vitamin Be imfortunately, other phenols occur in many products and the three forms of the vitamin do not, in general, yield equal color values. 

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