If you were to follow the progress of this reaction using IR spectroscopy, you would see Disappearance of a broad peak above 3000cm-1 Disappearance of a peak around 1700cm-1 Disappearance of a broad peak above 3000cm-1 and appearance of peak around 1700cm-1 Disappearance of a peak above 1700-cm1 and appearance of a broad peak around 3000cm-1 QUESTION 2 If you were following this reaction using Mass spec, a strong peak at M/z of 28 would indicate: Complete conversion of the reactant to product possible side reactions presence of unreacted aldehyde a high yielding reaction QUESTION 3 If the proton NMR showed a singlet and 2 doublets clustered between 7-8ppm. You can infer that: The conversion from aldehyde to alcohol was incomplete there was no reaction does not provide any information regarding the success of the reaction. The reaction was high yielding.
Background Information
In a 125 mL Erlenmeyer flask, dissolve 25.0 mmol of vanillin in 30 mL 1 M sodium hydroxide. If the mixture does not dissolve after 5 minutes of continuous stirring, add another 5 mL sodium hydroxide. Cool the solution to just below 15°C. In a small beaker, dissolve 12.0 mmol of sodium borohydride in about 6 mL of 1 M sodium hydroxide.
Remove the vanillin solution from the ice bath and add the sodium borohydride solution in small portions to the vanillin over a 5-minute period. Over time, the reaction mixture will warm up. Keep the temperature within the range of 20-25°C. If it is too cool, the reaction will proceed too slowly. If it is too warm, the product will not crystallize properly in the end. Once all of the sodium borohydride has been added, let the solution sit for 30 minutes, with frequent swirling.
Once the 30 minutes have elapsed, place the reaction mixture in an ice bath, cooling it to below 20°C. Acidify the solution with 6 M hydrochloric acid (6-10 mL may be required), keeping the temperature low. Perform this step carefully to prevent the temperature from spiking, but quickly enough so that “foaming” is observed. Once the yellow color has faded, check the pH with litmus paper to ensure that the mixture is acidic. Crystallization should have occurred during the neutralization process. If it has not, it may be necessary to seed the solution with crystals from another student. After neutralization is complete, ice the reaction mixture for 15 minutes prior to filtration.
Collect the vanillyl alcohol by vacuum filtration and wash the crystals with cold water. Store the product in a container specified by the instructor until next week. Once the sample has dried, determine its mass and melting point.
Clean up and waste disposal:
Questions
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If you were to follow the progress of this reaction using IR spectroscopy, you would see
Disappearance of a broad peak above 3000cm-1
Disappearance of a peak around 1700cm-1
Disappearance of a broad peak above 3000cm-1 and appearance of peak around 1700cm-1
Disappearance of a peak above 1700-cm1 and appearance of a broad peak around 3000cm-1
QUESTION 2
-
If you were following this reaction using Mass spec, a strong peak at M/z of 28 would indicate:
Complete conversion of the reactant to product
possible side reactions
presence of unreacted aldehyde
a high yielding reaction
QUESTION 3
-
If the proton NMR showed a singlet and 2 doublets clustered between 7-8ppm. You can infer that:
The conversion from aldehyde to alcohol was incomplete
there was no reaction
does not provide any information regarding the success of the reaction.
The reaction was high yielding.
QUESTION 4
-
The limiting reagent in this experiment is
vanilla
vanillin
sodium borohydride
sodium hydroxide
QUESTION 5
-
The gas evolved in this reaction is
carbon dioxide
nitrogen
oxygen
Hydrogen
QUESTION 6
-
Reduction reaction involves
Addition of hydrogens
removal of hydrogens
addition of oxygens
removal of H+
QUESTION 7
-
Theoretically, one mole of sodium borohydride can react with _______moles of vanilin
4
3
2
5
QUESTION 8
-
Care has to be taken to keep the reaction mixture at _________during the addition of HCl.
55 deg
25 deg
0 deg
15 deg
QUESTION 9
-
Sodium borohydride reduces___________ and ____________ but not _____________
aldehydes andketones not estersaldehydes and esters not ketones
alkanes and ketones not aldehydesaldehydes and ketones
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