Chapter 2 The nutrients in food
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What is the chemical formula of DCPIP, and what is the redox equation for its reaction with vitamin C?
Igloo writes ...
DCPIP, a dye often used to estimate the concentration of vitamin C, is a complex molecule with the common name 2,6-dichlorophenolindophenol (DCPIP for short!). Its systematic name is 2,6-dichloro-4-[(4-hydroxyphenol)imino]-2,4-cyclohexadien-1-one, and since you asked for it, its structure is:
I’ll leave you to try to match this structure with its systematic name!
The structure to the right of the central nitrogen atom of the molecule (as shown above) is typical of a dye, in this case a blue one.
When DCPIP is reduced by the vitamin C, I suspect that it gains two hydrogen atoms forming:
and, as you will know from the experiment, this product is colourless since it has lost the structural characteristics of DCPIP mentioned above.
In the meantime I believe that the vitamin C (ascorbic acid) is oxidised from
to
losing two hydrogen atoms in the process.
So, if I am correct, you can see that one mole of DCPIP will be reduced by one mole of ascorbic acid. I’ll leave you to construct the actual equation.
Whilst I can vouch for the structures of DCPIP and ascorbic acid, I am only suggesting the structures of the two products and have no documentary evidence to support these predictions.
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updated: 20 April 2004
