1. What is the purpose of sodium hydroxide in the reaction of reducing vanillin

Question

1. What is the purpose of sodium hydroxide in the reaction of reducing vanillin to vanillyl alcohol?

all my book says is that sodium borohydride reductions are commonly carried out in dilute aq sodium hydroxide solutions, but not why

I know that NaBH4 used in excess will increase the reaction rate but does that mean the reaction rate depends on the amount of it?

3.

not sure if this is right

4. Assume 0.66 kg of vanillyl alcohol is formed in this reaction. How many mmol of vanillin were required? (Really need help with the calculation, and writing out all of the calculations of how i got the answer)

#5.

Explanation / Answer

1. The purpose of NaOH in the reduction of vanillin is,

- to keep the sodium borohydride solution at high pH

This allows for no or less decomposition of NaBH4 by acidic groups of vanilin.

2. NaBH4 is used in excess. The fact that the reaction is first order with respect to NaBH4 mean,

- The rate of reaction depends upon amount of NaBH4 added

3. The effect of running this reaction at room temperature,

Unwanted by-products tend to form at at higher temperatures which reduces yield.

4. 1 mole of Vanillin gives 1 mole of alcohol product.

moles of vanillin required = moles of vanillyl alcohol = 0.66 kg/154.17 g/mol = 4.3 mols

5. An IR band in the range 1750-1630 cm-1 on vanillin is due to,

- aldehyde

6. Proton shift for -OH group would be,

3-5 ppm

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