Nucleophilic Addition to a Carbonyl: the Grignard Reaction

Topics: Alcohol, Functional groups, Grignard reaction Pages: 4 (1159 words) Published: October 7, 2008
The experimental laboratory procedures were divided into two categories. First the formation of phenylmagnesium bromide, and second the reaction of the phenylmagnesium bromide with the carbonyl compound. However, before any of this could be done, the refluxing apparatus for the Grignard reaction was to be flame dried until no moisture remained inside because any water would cause the reagent to decompose and an alkane to form. The reaction would subsequently fail. Drierite was placed inside a plastic drying tube as a drying agent, absorbing all the moisture from the solvents that would later be refluxing in the apparatus and coming out into the atmosphere. After setting this up, researchers continued to crush magnesium turnings into smaller pieces in order to expose fresh metal by removing possible magnesium oxide that was on the surface of the turnings. The turnings were added to the round bottom flask as well as an iodine crystal, which facilitates the reaction by cleaning the surface of the magnesium metal. Bromobenzene and anhydrous diethyl ether were then added to the flask. Anhydrous ether was used because at this point, no water was to enter the reaction. The reaction was triggered by swirling and the heat of a human hand. From here, the refluxing began and ended once the bromobenzene addition was completed.

The second phase of the experiment involved the reaction of the phenylmagnesium bromide with assigned carbonyl compound. Appropriate amounts of benzaldehyde, benzophenone, or methyl benzoate based on the amount of bromobenzene used should be added to a dry beaker along with anhydrous diethyl ether. The mixture was poured into the addition funnel, added to round bottom flask drop wise, allowed to reflux for an additional 15 minutes, and then cooled it to room temperature. Once the reaction mixture was cooled, it was poured onto 25g of ice and H2SO4. Diethyl ether was added to completely dissolve any remaining solids. The ether did not...
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