grignard synthesis

Topics: Diethyl ether, Alcohol, Magnesium Pages: 4 (514 words) Published: June 19, 2014
Lab 3: Grignard Synthesis

Objective:
The goal of this lab is to synthesize a Grignard reagent from bromobenzene and magnesium metal in diethyl ether. This same Grignard reagent would then be used to prepare a tertiary alcohol and then purify and characterize the product.

Table of Reagents:

Name
Chemical formula
Melting Point
Boiling Point
Density
Safety Hazards
Diethyl ether
C4H10O
-116.3°C
34.6°C
0.7134 g/ml
Flammable
Bromobenzene
C6H5Br
-30.6°C
156°C
1.5 g/ml
Irritant. Avoid contact with skin, eyes and clothing
Acetophenone
C6H5COCH4
19.7°C
202°C
1.033 g/ml
Irritant. Avoid contact with skin, eyes and clothing
Hexane
C6H14
-95°C
69°C
0.6548 g/ml
Flammable

Procedure:
Refer to the microscale lab in pages 124-130 (15.1 and 15.2) in Modern Projects and Experiments in Organic Chemistry: Miniscale and William Microscale.

Observations:
Mixture of magnesium with bromobenzene turned into a yellow coloration after the bubbling. After much heating, the mixture turned 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.

Data:
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: 80°C-81°C

Calculations:

acetophenone is the limiting reagent

Analysis:
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 80°C-81°C, which is the same as its literature value. This means that there was no or very little impurity in the recrystallization process

From the IR, it is evident that the hydroxyl group...
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