I have been given the below information and asked to calculate the amount solvent and reactants needed to be used to obtain 1.0 g of the product.

Benzyltriphenylphosphonium chloride. In a 100 mL round bottom flask (rbf), 5.2 g triphenylphosphine was dissolved in 20 mL benzene. Benzyl chloride (2.28 mL) added to the rbf through the reflux condenser with a syringe. Refluxed 1 hr, solution became cloudy. Rbf contents vacuum filtered, white crystals washed with ether. Mass benzyltriphenylphosphonium chloride collected 3.1 g.

Please help

I don't know exactly what your teacher expects but the easy way to do it, especially if you don't want EXACT answers, is to multiply the grams used by the factor 1/3.1. I realize this factor is mass/mass but you can use it on the volumes also. The harder way is to convert the reactants to mols, convert product to mols, determine the yield, and work backwards from there. You will have 1.0 g of product, divide by yield, convert that to mols product, that will be the same as mols reactants (in this problem), and convert to grams reactants. I tried it both ways and the numbers are essentially the same, especially when we note that the number of significant figures is small. If you need further assistance, please post your work and tell us where you are stuck. We can help you through it. Thanks for posting on Jiskha.

Anonymous Anonymous answered
16 years ago

why should benzyl chloride be added with a syringe