I have researched multiple mechanisms for this experiment yet all of them suggest different versions or are too vague. None of them are consistent since the final overall equation seems to be missing a few elements. Can someone help me out?
Step 1: $\ce{O2(g) -> O2(aq)}$ (Fast)
Step 2: $\ce{O2(aq) + MBred (aq) -> MBox (aq)}$ (Fast)
Step 3: $\ce{MBox (aq) +C-(aq) -> MBred (aq) + X-(aq)}$ (Slow)
The general mechanism that showed up frequently is very vague. The $\ce{X-}$ is always labeled as the oxidation products of the carbohydrate. I can't seem to specifically find the product for any of the carbohydrate (glucose, fructose etc.). On top of that, from my understanding of the reaction mechanisms is that each step must be balanced and in the end, intermediate species are canceled out. However, the same issue always comes out with the leftover elementary species $\ce{O2}$ where the overall equation is then not balanced. For example:
Prior to the addition of MB: $$\ce{C6H12O6(aq) + OH-(aq) <=> C6H11O6-(aq) + H2O(l)}$$
Step 1: $\ce{O2(g) -> O2(aq)}$ (Fast)
Step 2: $\ce{O2(aq) + MBred (aq) -> MBox (aq)}$ (Fast)
Step 3: $\ce{MBox(aq) + C6H11O6-(aq) -> MBred (aq) + C6H10O6(aq)}$ (Slow)
is the best possible mechanism I could put together and step 3 makes sense to me since the 2 $\ce{H+}$ ions will be used to reduce the methylene blue. but then the overall equation will look like:
$$\ce{O2 + C6H11O6-(aq) -> C6H10O6(aq)}$$
where it is now missing the balance in hydrogen and oxygen.