Question

1.

a) draw the structure of the product you would have isolated if you had used NaBD4 in D2O in this experiment, write a mechanism explaining the result.

(b) give the product structure for the same reaction using NaBD4 in H2O. Assume that there is no hydrogen exchange between NaBD4 and the solvent.

Not sure if this is relevant to the question but here is the procedure used:

Dissolve 3.8g of vanillin in 12mL of ethanol in a small beaker (you may have to warm it in your hand) and add a sitr bar. Dissolve 0.5g of NaBH4 in 5mL of 1M NaOH in a small Erlenmeyer flask. Cool both solution in water bath that has been cooled to 15°C with ice chips. using a dropped, slowly add NaBH4 solution drop by drop to the vanillin solution making sure the temperature stays around 15°C. It should take around 10 minutes. Once the addition is complete, let the reaction warm to room temperature for 30 minutes with stirring. To isolate the product, carefully add 6M HCl dropwsie, making sure to let the bubbles and foaming subside before adding another drop. Do this until the pH is less than 2. Collect the vanillyl alcohol percipitate by vacuum filtration. Recrystallize by dissolving in 12mL of hot water and then allowing the solution to cool first to room temperature and then to 0°C using an ice bath. Filter, dry and weigh product and record its melting point.

Answer 1

Drawn below is the product formed from the reation of vanillin with NaBD4 in D2O solvent. The first step is addiiton of deutarate to carbonyl carbon to form an O- species which is hydrlyzed in D2O solvent to form -OD alcohol.

Drawn below is the product formed by reaction of vanillin with NaBD4 in H2O solvent. Here the first step remains as above but the second step we get hydrolysis with H2O to form -OH alcohol.