Alkene Addition
Essay by people • July 29, 2011 • Essay • 425 Words (2 Pages) • 2,413 Views
Lab 1: Alkene Addition
Introduction:
Lab 1 involved using experimental methods to determine and further understand the process of alkene addition, specifically through the bromination of (E)-stilbene. Within this process, a polarized electronic deficient bromine is added across an electron rich nucleophilic double bond, forming a three membered ring positively charged bromonium ion. The remaining bromide ion acting as a nucleophile attacks either side (top or bottom) of each carbon making up the double bonds from the opposite (anti) or same side (syn) of the positively charged bromonium ion ultimately opening up the ring system. The anti reaction results in a meso compound while syn addition forms the racemic product. In some cases a mixture of both meso and racemic products may result. The goal of this experiment was to identify the final favored intermediate product. Such a determination was made through comparison between experimental and known scientific literature regarding such properties as unique stereochemistry and melting point values for each possible product.
Mechanisms:
Experimental Details:
Reactants and Products MW (g/mol) Quantity (g or mL) Mass/MW (mol) Mp (C) Bp (C)
Acetic acid 60.05 4 mL 0.0666 16.5 118-119
meso-1,2-dibromo-1,2-diphenylethane 340.07 0.297 g (yield) 0.0009 (yield) 241 NA
Racemic-1,2-dibromo-1,2-diphenylethane 340.07 NA NA 113
pyridinium bromide perbromide 319.84 0.390 g 0.0012 135-137 NA
E-stilbene sample 180.25 0.2 g 0.0011 122-124 NA
pyridinium bromide perbromide observation addition produced cloudy deep orange color
Addition: methanol 2 1-mL portions, with excess
Final product white crystalized product
Results:
Theoretical yield:
(number mol -1,2-dibromo-1,2-diphenylethane = Mass of 1,2-dibromo-1,2-diphenylethane) / (MW of 1,2-dibromo-1,2-diphenylethane)
(0.0011 mol) x (340.07 g/mol )= 0.374 g meso-1,2-dibromo-1,2-diphenylethane
Percent yield:
Actual yield / Theoretical yield * 100
(0.297g) / (0.374g ) x 100= 79.41% yield of meso-1,2-dibromo-1,2-diphenylethane
Mass:
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