Grignard synthesis essay


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The goal of this lab is always to synthesize a Grignard reagent from bromobenzene and magnesium (mg) metal in diethyl azure. This same Grignard reagent would then be used to prepare a tertiary liquor and then detox and define the product.


Refer to the microscale research laboratory in web pages 124-130 (15. 1 and 15. 2) in Contemporary Projects and Experiments in Organic Biochemistry and biology: Miniscale and William Microscale.


Mixture of magnesium with bromobenzene turned into a yellow toque after the bubbling. After very much heating, the mixture changed into a brownish-mahogany color.

The mixture did not recrystallize after being placed in an ice water bath (this was after the separation of diethyl ether). It had to be heated once again in order for crystals to form.


Mass of magnesium: .074 grams

Mass of 1,1-diphenylethanol: .037 grams

Bromobenzene used: .32 mL

Acetophenone used: .23 mL

Melting range of 1,1-diphenylethanol: 80C-81C


acetophenone is the limiting reagent


The main goal of this lab was to create a Grignard reagent and then use that same reagent to produce a tertiary alcohol.

This was accomplished by reacting the Grignard reagent with acetophenone. The end product was 1,1-diphenylethanol. Its recorded melting point range was 80C-81C, which is the same as its literature value. This means that there was no or verylittle impurity in the recrystallization process

From the IR, it is evident that the hydroxyl group (-OH), around 3400 cm-1, is present in this product. There is also a presence of “CH bonds that come from aromatic ring structures at around 3000 cm-1. C-C bonds from aromatic structures can be seen at around 1500 cm-1.

The percent yield 22.35%. The reason for such a low yield could be due to the quenching of the Grignard reaction and the isolation of the product. It is possible that the product was lost during the filtration process.

1. If phenylmagnesium bromide were prepared, and any water was present in the reaction mixture, phenylmagnesium bromide would be quick to react with water, stealing one of its hydrogens. This hydrogen would therefore replace the attached “MgBr to form benzene.

Ph -MgBr + H2O “>Ph-H & HOMgBr

installment payments on your The Grignard synthesis would not proceed since Grignard reagents react quickly with alcohols due to their level of acidity, which will make them fantastic nucleophiles. Using ethanol could ruin the Grignard reagent before the carbonyl is added, which could consequently lowering the deliver.

3. Magnesium + I2 MgI2

5. The reason why bromobenzene substrate is added in two portions, rather than one particular full part, is because adding it all simultaneously would trigger an increase in the product 1-phenylethanone and very small phenylmagnesium bromide would be create. Without phenylmagnesium bromide, the synthesis of just one, 1-diphenylethanol probably would not be able to arise.


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