preview

Greener Brominations Essay

Decent Essays

Greener Brominations

Abstract

In this experiment, trans-stilbene was brominated and debrominated with the use of three methods: bromination with pyridinium tribromide, bromination with hydrogen peroxide and hydrobromic acid, and debromination with zinc. The yields of parts A, B, and C are as follows: 68.6 %, 54.6 %, and 55.9 %.

Introduction

In the chemical process of bromination, an alkene is halogenated with bromine. Solvents that are typically used include methylene chloride and carbon tetrachloride along with iodine, the traditional reagent. However, because of the carcinogenic properties of the solvents and the corrosiveness of iodine, other alternatives are utilized : bromination with pyridinium tribromide, bromination …show more content…

Finally, the product yield and melting point were recorded.

1Student Notes: Greener Brominations of Stilbene,

Data

molecular weight of (E)-stilbene 180.23 g/mol melting point (lit.) 122-124 °C

molecular weight of stilbene dibromide 338.02 g/mol melting point (lit.) 236-240 °C

A. Bromination of trans-stilbene with pyridinium tribromide

(E)-stilbene 2.0 g filter paper 0.4483 g watch glass 24.4018 g final 27.4208 g product (stilbene dibromide) 2.5707 g melting point 238 °C

Theoretical Yield
= molar quantity of limiting reagent * molar mass of product
= (2.0 g (E)-stilbene / (180.23 g/mol)) * ( (338.02 g/mol) stilbene dibromide)
= 3.75 g

Fractional Yield
= (Actual Yield / Theoretical Yield) * 100 % = (2.5707 g / 3.75 g) * 100 %
= 68.6%

B. Bromination of trans-stilbene with hydrobromic acid and hydrogen peroxide

(E)-stilbene 0.51 g filter paper 0.5184 g final 1.0407 g product (stilbene dibromide) 0.5223 g melting point 220-222 °C

Theoretical Yield
= molar quantity of limiting reagent * molar mass of product
= (0.51 g (E)-stilbene / (180.23 g/mol)) * ((338.02 g/mol) stilbene dibromide)
= 0.957 g

Fractional Yield
= (Actual Yield / Theoretical Yield) * 100 % = (0.5223 g / 0.957 g) * 100 %
= 54.6%

C. Debromination of stilbene dibromide with zinc

stilbene dibromide 0.52 g filter paper 0.6070 g final 0.7618 g product 0.1548 g
melting

Get Access