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Sodium Borohydride Reduction of Acetophenone

Sabrina(Jingyao) Liao

Simpson University / Organic Chemistry II


The purpose of this experiment is to synthesize 1-phenylethanol from acetophenone using sodium borohydride as the reducing agent.



Table of reactants and reagents 





Molar mass









202.4 celcius/20.2 celcicius


Sodium borohydride

1.509 g

0.040 mol

37.83 g/mol


500 celcius/ 400celcius




0.33 mol

36.49 g/mol

1.2 g/cm3






0.514 mol

46.07 g/mol


78.37celciu/ 104 celcius


Methylene chloride

20 ml

0.41 mol

50.49 g/mol


39.6 °C celcius/ −96.7 °Ccelcius

Solvent for extraction

Magnesium sulfate 

2 scoops


120.366 g/mol

2.66 g/cm3

330 celcius/ 1124 celcius

Drying agent

  • Mass of empty 100ml round bottom flask:  62.624g


  • Acetophenone no. of mol: 12.086g / 120.4g/mol= 0.10 mol 

  • Sodium borohydride no. of mol: 1.509 g / 37.83 g/mol= 0.040 mol

  • Hydrochloride no. of mol: (1.2 g/cm3= 1.2 g/ml) mass= 10ml x 1.2g/ml=12 g; no. of mol= 12g /36.49 g/mol=0.33 mol

  • Ethanol no. of mol: mass=0.79 g/ml x 30ml =23.7 g; no.mol=23.7g /  46.07 g/mol= 0.514 mol

  • Methylene Chloride no. of mol: mass= 1.03g/ml x 20ml= 20.6 g; no. mol=20.6g/ 50.49 g/mol=0.41 mol


 Figure. 1. Set up of distillation apparatus

Firstly, A magnetic stir bar was placed inside a 150ml beaker with 1.509 g sodium borohydride inside. Then, 30 ml of 95% ethanol was added into the beaker which was then placed on a stirring plate to get mixed thoroughly. Thirdly, 12.089 g of acetophenone was weighed and obtained inside a 125ml- Erlenmyr flask. Around 0.5 ml of acetophenone was added into the Erlenmyer flask every 2 minutes until all of the acetophenone was inside the flask. The addition process took 35 mins in total and white precipitation was observed during the process. After that, the Erlenmyer flask was cooled down by an ice bath, followed by being placed on the stir plate at room temperature for 20 minutes. Then, 10 ml of HCl was added to the mixture in a fume hood. Afterward, the flask was placed on a hot plate and heated for 15 minutes to get rid of the ethanol. The mixture was then transferred into a separatory funnel and 20ml of methylene chloride was added into the funnel. To rinse off the remained mixture on the wall of the flask into the separatory funnel, 30ml of H2O was used. The funnel was then shaken thoroughly, followed by the solution being left to stand to allow the layers to settle. After that, the mixture was purified by the bottom layer(CH3Cl2) being drained. Another 20 ml of methylene chloride was added into the funnel and the bottom layer was drained again. The mixture was filtered into a preweighed 100ml-round bottom flask (weighed 62.624g) by using a glass funnel with filter paper in it. A distillation apparatus was set up as in the picture shown above (Fig 1.). Eventually, 10.10 g of  1-phenyl ethanol was distilled. The IR spectrum of the product was then examined by an IR spectrometer. 

Table of products



Yield (mol)

Theoretical yield (g)

Molar mass

Percent yield



 1-phenyl ethanol

10.10 g

12.1 mol

4.89 g

122.16 g/mol


20 celcius / 205 celcius

1.012 g/cm3


  • Yields of 1-phenylethanol= 72.726g- 62.624g(mass of 100ml round bottom flask)= 10.10 g

  • 1-phenyl ethanol no. of mol: 122.16g/mol / 10.10 g =12.1 mol

  • Theoretical no. of moles of 1-phenylethanol= Sodium borohydride no. of mol(since it’s limiting reactant) = 0.04 mol

  • Theoretical yield of 1-phenyl ethanol: theoretical mass=0.04 mol x 122. 16 g/mol= 4.89 g

  • Percent yield: %= 10.10 g/4.89 g= 2.07 =207%


The IR spectrum of starting material (Fig 3.) and product (Fig 2.) is shown in the images below. In the IR spectrum of acetophenone (starting material), a distinctive peak is observed at 1700 cm^-1. This indicates the presence of a conjugated carbonyl group. However, in the IR spectrum of 1-phenylethanol (product), this peak is notably absent, suggesting the carbonyl group was gone after the synthesis process. Conversely, the IR spectrum of 1-phenylethanol illustrates a prominent peak at 3345.11 cm^-1, corresponding to the presence of an alcohol functional group, indicating the product was made. This peak is not observed in the spectrum of acetophenone. 

In conclusion, based on the IR result obtained,  1-phenyl ethanol was successfully synthesized from acetophenone by reacting with sodium borohydride and hydrochloride. The percentage yield of 200 percent might be due to the impurities of the products caused by inefficient extraction or incomplete drying when using magnesium sulfate.

Figure 2. Experimental product IR spectrum

Figure 3. IR spectrum of starting material

Works Cited

PubChem. “PubChem.”, National Library of Medicine, 2022,


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