Grignard Reagent Lab Report

This reaction is an example of the synthesis of a carboxylic acid utilizing a Grignard reagent. The reaction starts with the formation of a Grignard reagent; when the bromine on bromobenzene bonds to magnesium metal using the solvent, anhydrous diethyl ether. Using an ether is important due to the ability for its lone electron pairs help to stabilize the positive charge on magnesium. Once the Grignard reagent is obtained, the carbon, from the dry ice, will kick off the magnesium bromide and replace it. As this happens, water is reacted with it and thus adds a hydrogen onto the single bonded oxygen. Figure 1 shows the sublimation of dry ice with the Grignard reagent during this step. This will create an alcohol, specifically benzoic acid. After this step, the compound has replaced the magnesium bromide on the cyclohexane. In addition, biphenyl is produced as a side product. In the next step, addition of sodium hydroxide, the sodium will replace the hydrogen on the alcohol. Upon addition of HCl, the benzoic acid is freed from its salt and precipitates out of solution. Figure 3 shows the finished product of the Benzoic acid obtained. The product was a fine white powder.

The actual melting point of benzoic acid is known to be 122.4°C. Also, looking at Table1, the percent yield is shown to be 44.9%. The percent yield is how much product was recovered after the reaction was carried out. The percent yield can be used to explain why the melting point observed in the experiment didn’t match the known melting point. Obtained melting points are generally lower than the literature value melting points of a substance due to the number of impurities present in the obtained product. The percent yield of 44.9%, validates that the product could have had some impurities present, and thus the lower melting