Organic Chemistry

Into a 3-ml conical vial, 3.80mmol of benzophenone was dissolved in 2.0ml of anhydrous ethyl ether . When the reaction cooled, after the ether stops boiling, the septum cap was removed, and a dry stir bar was dropped into the reaction flask and the cap was replaced afterwards. The stirrer was started. A syringe was used to add about three drops of benzophenone solution at a rate sufficient to keep the reaction mixture boiling gently without external heating.

When the addition was complete, 0.5ml anhydrius ether was used to rinse the vial that contained benzophenone solution. A warm water bath was used to heat the reaction mixture for another ten minutes, while stirring with stir bar still in the solution.

The reaction was then allowed to cool to room temperature. A syringe was used to add 1.0ml of water drop by drop to the reaction flask, and the reaction is allowed to subside. While stirring, 2.0ml of 5% (1.4M) hydrochloric acid was added to the reaction. When all the reaction subsides, and all the white solid dissolved, stirring was stopped.

The reaction was transferred to a centrifuge tube using a small amount of solvent-grade ether, leaving the stirr bar and any undissolved magnesium behind. The solution was shaked gently to mix the layers thoroughly. Emulsion might formed in the solution, but a wooden applicator stick was used to break it up.

The aqueous layer was removed and discarded from the solution circumspectly. The remaining solution was washed with 3ml of 5% aqueous soldium bicarbonate, and then with 3ml of saturated aqueous soldium chloride. The ether solution was then dried with anhydrous magnesium sulfate. Then the ether was evaporated and a solid residue was left behind.

To the solid residue, 2.0ml of hexane was added. A flat-bladed microspatula was used to rub and grind the solid in the solvent for 2-3minutes. The product was collected by vacuum filteration. The product, crude phenylmethanol, was then recrystallized from a 2/1 mixture of hexane with absolute ethanol. Triphenylmethanol crystals was allowed to form (slowly) for about 30minutes.It was dried, weighed and it's melting point was recorded.

Result:

The final weight of product obtained from the reaction was 0.51grams, and the melting point ranged from 132-140oC. The actual melting point of triphenylmethanol is 164oC.

The percent yield of the product obtained is as follows :

(0.00380mol benzophenone)/1 x (1mol triphenylmethanol)/(1mol benzophenone) = 0.00380mol triphenylmethanol

Theroetical yield : moles of triphenylmethanol x molecular weight of triphenylmethanol

0.00380mol x 260.33g/mol = 0.989grams.

Percent yield = (actual yield)/(theoretical yield) x (100 %)/1

Percent