Question

Hi, I am doing an experiment that is called NaBH4 reduction of acetophenone. I am having trouble understand the techinque/wording when using a sep funnel. These are some of the procedures below:

1. Pour the mixture into a separatory funnel and add 20 mL of ice water. Rinse the beaker with additional ice water (5 mL) and add the rinsing to the separatory funnel. Rinise the beaker with ether (2 X 15 mL), adding the ether to the separatory funnel.

2. shake mixture, vent, and then remove the ether layer and set aside. Most of the product should be in the ether layer

3. extract the aqueous layer with ether (2 x 25 mL) to remove the remainder of the product. Combine all ether layers in a common beaker

(The multiply sign means the number of times you do it)---however can someone explain to me more clearly of that the steps tell you to do?

Answer 1

Sodium borohydride is a good reducing agent. it is very effective for the reduction of aldehydes and ketones to alcohols. the reduction of acetophenone to 1-phenylethanol. in this after completion of reaction (total starting material converted into Product) we have to quinch the sodium borohydride reagent with ice-water (if excess present in the reaction). then isolation of product from reaction mxture. as procedure follow

1. Pour the mixture into a separatory funnel and add 20 mL of ice water. Rinse the beaker with additional ice water (5 mL) and add the rinsing to the separatory funnel. it means when adding ice water excess reagent quinched with ice water and some inorganic complexes will go into the water.

Rinise the beaker with ether (2 X 15 mL), adding the ether to the separatory funnel- rinising the beaker with ether for if product reamin into the beaker it will come with ether, because product not soluble in ice water.

2. shake mixture, vent, and then remove the ether layer and set aside. Most of the product should be in the ether layer mixing the ice water and ether mixture , all product will go to the ether, sodim and boric acid complexex will go in to the water. when settle (kept aside) some time both ether and water layers will seperate(due to density water come bottom layer the other ether top layer)

3. extract the aqueous layer with ether (2 x 25 mL) to remove the remainder of the product. Combine all ether layers in a common beaker - the above layers separation top ether kept aside, bottom aqueous layer add in to separating funnel then ether, mix well and seperate(same above) the layers. this is one more time because mentioned two times. the purpose of this is extraction of product in aqueous layer if any thing small amount remains.