Grignard Reaction Lab Report

Carly Greenhoe

CM 261 W 1:15- 5:15

Dr. Batten

Lab 8: The Grignard Reaction

Goal:

The purpose of this experiment was to explore the synthesis of triphenylmethanol through the use of a Grignard reagent. The Grignard reaction is one of the most versatile methods of forming carbon-carbon bonds thus the fact that Grignard reagents can be made from pretty much anything. In this experiment the reagent was produced by preparing phenyl magnesium bromide by reacting bromobenzene with magnesium turnings. In this lab, reflux, extraction, rotovaping, gravity filtration, recrystallization, melting point determination, and infrared spectrometry (IR spectrometry) will all be techniques exercised. The application of infrared spectroscopy will be used for positive identification of the product.

Reactions:

The Alternate Grignard Reaction:

Equipment Directions and Reaction Setups:

A reflux apparatus with a water-jacketed condenser and an addition funnel were assembled and used to form the Grignard reagent. This was built from the bottom up, starting with the 250mL round-bottom flask, yet leaving enough space underneath the flask for a beaker of warm water to be placed under it at a later time in the experiment. Once the three pieces were assembled, but not yet clamped, the apparatus was dried out with a flame. This was done in a similar manner as it was assembled, from the bottom upward, driving any moisture in, out of the structure. Once the drying process had been completed a drying tube was placed on top of the condenser and a stopper in the addition funnel preventing any moisture from reentering the apparatus. The drying process is very important because the Grignard reagent reacts with compounds such as water, so moisture must be kept out. The method used for preparing a pellet for IR in this experiment was the minipress method. 10 parts of KBr and 1 part triphenylmethanol were mixed using a mortar and pestle. When sufficiently mixed, a small portion of the...