Grignard Synthesis Essay

September 11, 2017 Chemistry

Aim:
The end of this lab is to synthesise a Grignard reagent from bromobenzene and Mg metal in diethyl quintessence. This same Grignard reagent would so be used to fix a third intoxicant and so sublimate and qualify the merchandise.

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.

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Observations:
Mixture of Mg with bromobenzene turned into a xanthous colour after the bubbling. After much warming. the mixture turned into a brownish-mahogany colour. The mixture did non recrystallize after being placed in an ice H2O bath ( this was after the separation of diethyl quintessence ) . It had to be heated one time once more in order for crystals to organize.

Datas:
Mass of Mg: . 074 gms
Mass of 1. 1-diphenylethanol: . 037 gms
Bromobenzene used: . 32 milliliter
Acetophenone used: . 23 milliliter
Melting scope of 1. 1-diphenylethanol: 80°C-81°C




Calculations:

acetophenone is the confining reagent

Analysis:
The chief end of this lab was to make a Grignard reagent and so utilize that same reagent to bring forth a third intoxicant. This was accomplished by responding the Grignard reagent with acetophenone. The terminal merchandise was 1. 1-diphenylethanol. Its recorded thaw point scope was 80°C-81°C. which is the same as its literature value. This means that there was no or really small dross in the recrystallization procedure

From the IR. it is apparent that the hydroxyl group ( -OH ) . around 3400 cm-1. is present in this merchandise. There is besides a presence of –CH bonds that come from aromatic ring constructions at around 3000 cm-1. C-C bonds from aromatic constructions can be seen at around 1500 cm-1.

The per centum output 22. 35 % . The ground for such a low output could be due to the extinction of the Grignard reaction and the isolation of the merchandise. It is possible that the merchandise was lost during the filtration procedure.

1. If phenylmagnesium bromide were prepared. and any H2O was present in the reaction mixture. phenylmagnesium bromide would be speedy to respond with H2O. stealing one of its Hs. This H would therefore replace the affiliated –MgBr to organize benzine.

Ph -MgBr + H2O — & gt ; Ph-H + HOMgBr

2. The Grignard synthesis would non continue because Grignard reagents react rapidly with intoxicants due to their sourness. which would do them highly good nucleophiles. Using ethyl alcohol would destroy the Grignard reagent before the carbonyl is added. which would accordingly cut downing the output.

3. Mg + I2 MgI2

4. The ground why bromobenzene substrate is added in two parts. instead than one full part. is because adding it all at one time would do an addition of the merchandise 1-phenylethanone and really small phenylmagnesium bromide would be produce. Without phenylmagnesium bromide. the synthesis of 1. 1-diphenylethanol would non be able to happen.

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