We made t-pentyl Chloride in Lab today using HCl and t-pentyl alcohol. I know t-pentyl chloride is not soluble in water, but I'm still not sure the answer to some of my post lab questions. I've answered a few, but I have 3 that still confuse me. We performed a water extraction followed by an extraction with 5% NaHCO3.
1) What impurity or impurities does the water extraction remove?
2) What impurity or impurities does the NaHCO3 extraction remove?
and 3) Why is the water extraction done before the NaHCO3 extraction?
I believe NaHCO3 removes some of the excess HCl, but I'm not confident enough and I'm not sure if that's the only thing it removes. Please help!
1) The water extraction removes impurities that are water-soluble. In the case of making t-pentyl chloride, some of the impurities that could be removed by water extraction include unreacted t-pentyl alcohol, residual HCl, and any byproducts that are more soluble in water than in the organic solvents used.
To perform the water extraction, you would typically add water to the reaction mixture of t-pentyl chloride, HCl, and t-pentyl alcohol in a separatory funnel. Since t-pentyl chloride is not soluble in water, it will separate into a distinct organic phase. After shaking and allowing the layers to separate, you would carefully drain the aqueous layer from the bottom, effectively removing the water-soluble impurities with it.
2) The NaHCO3 extraction removes acidic impurities. In the case of making t-pentyl chloride, the main acidic impurity would be residual HCl.
To perform the NaHCO3 extraction, you would typically add a 5% solution of sodium bicarbonate (NaHCO3) to the organic phase remaining in the separatory funnel after water extraction. The HCl will react with the NaHCO3 to form carbon dioxide gas and salt (sodium chloride). The carbon dioxide gas will bubble out of the solution. After shaking and allowing the layers to separate, you would drain the aqueous layer again, effectively removing the acidic impurities, including excess HCl.
3) The water extraction is done before the NaHCO3 extraction because water is more polar than the organic solvents used in the reaction. This means that water has a higher affinity for dissolving water-soluble impurities compared to the organic solvents. By performing the water extraction first, you remove the majority of the water-soluble impurities, ensuring a cleaner organic phase before proceeding to the NaHCO3 extraction.
The NaHCO3 extraction specifically targets acidic impurities, such as residual HCl. By performing it after the water extraction, you reduce the risk of carry-over of acidic impurities into the NaHCO3 extraction step, which could interfere with the effectiveness of the NaHCO3 extraction process.
Overall, the combination of water extraction followed by NaHCO3 extraction helps to purify the t-pentyl chloride and remove both water-soluble impurities and acidic impurities.