Use the arrows above!
Tartrate is potassium sodium 2,3-dihydroxybutanedioate. Write a partial structural formula.
$Na^+$ $^-OOCCH(OH)CH(OH)COO^-$ $K^+$ . We subsequently call this substance $cpx$
What is the formula of a of copper(II) sulfate solution ?
$Cu^{2+}$ $+$ $SO_4^{2-}$.
Adding tartrate, forms a dark blue chelate (the Fehling reagent) which we shall write $[Cu(cpx)_2]^{2+}$. Simplified equation?
$Cu^{2+}$ $+$ $2cpx$ $\rightarrow$ $ [Cu(cpx)_2]^{2+}$.
Glucose is converted by oxidation to the corresponding carboxylic acid. Oxidation equation?
$C_5H_{11}O_5CHO$ $-$ $2e^-$ $+$ $H_2O$ $\rightarrow$ $C_5H_{11}O_5COOH$ $+$ $2H^+$
This reaction proceeds under basic conditions here and in addition the carboxylic acid is converted to carboxylate ion. Oxidation equation ?
$C_5H_{11}O_5CHO$ $-$ $2e^-$ $+$ $3OH^-$ $\rightarrow$ $C_5H_{11}O_5COO^-$ $+$ $2H_2O$
The complexed $Cu^{2+}$ ion is reduced to copper(I) oxide (brick red precipitate) by releasing the complexing agent. Reduction equation in basic medium? ?
$2Cu(cpx)_2^{2+}$ $+$ $2e^-$ $+$ $2OH^-$ $\rightarrow$ $Cu_2O$ $+$ $H_2O$ $+$ $2cpx$
Establish the complete redox system!
$C_5H_{11}O_5CHO$ $-$ $2e^-$ $+$ $3OH^-$ $\rightarrow$ $C_5H_{11}O_5COO^-$ $+$ $2H_2O$
$2Cu(cpx)_2^{2+}$ $+$ $2e^-$ $+$ $2OH^-$ $\rightarrow$ $C_5H_{11}O_5COO^-$ $+$ $Cu_2O$ $+$ $H_2O$ $+$ $2cpx$
$2Cu(cpx)_2^{2+}$ $+$ $C_5H_{11}O_5CHO$ $+ $ $5OH^-$ $\rightarrow$ $Cu_2O$ $ +$ $2cpx$ $+$ $C_5H_{11}O_5COO^-$ $ +$ $3H_2O$