Borohydride Reduction

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John Heger
CMY 211
Lab Section 13
Borohydride Reduction of Vanillin to Vanillyl Alcohol
Introduction: The purpose of this lab was to reduce vanillin to vanillyl alcohol. This lab report recaps the procedure and results of the lab. The chemical process studied in this lab was reduction, the process of reducing the number of bonds to oxygen and increasing the number of bonds to hydrogen. Other chemical processes included in the lab were recrystallization, melting point, and extraction. Procedure: Preparation of Vanillyl Alcohol

2.5 mmol of vanillin were dissolved in 2.5 mL of 1 M NaOH solution in a 25 mL Erlenmeyer flask. The flask was swirled to produce a homogeneous yellow solution. The flask was swirled in an ice-water bath for 1-2 minutes and the solution was cooled to approximately 10°C. 1.95 mmol of NaBH4 was added while the solution was constantly swirled. It was added in three to four portions over a period of 3 minutes. The solution was allowed to stand undisturbed for 30 minutes at room temperature. After the time period, the flask was cooled in an ice-water bath and 3 M HCl was added dropwise with swirling. HCl was added until the pH of the solution was distinctly acidic to pH paper. The solution was gently cooled and the side of the flask was gently scratched with a glass rod to induce recrystallization. The crude product was suction filtered using a Buchner or Hirsch funnel and was washed with three small portions of cold water. The crystals were allowed to air dry for several minutes while suction continued to eliminate excess water. The crude product was recrystallized from ethyl acetate. The dried crystals were weighed and a melting point was obtained. Results:

Table 1: Experimental Data Table
Initial Mass of Vanillin| 0.3843 g|
Final Mass of Vanillyl Alcohol| 0.2467 g|
Melting Point Range of Vanillyl Alcohol| 75-90°C|
Percent Yield| 63.99 % yield|

Discussion: The purpose of this lab was to...