1,1-diphenylethanol preparing from benzene and ethanol | Methyldiphenylcarbinol

1,1-diphenylethanol is an alcohol compound with two phenyl groups (benzene). Two benzene groups are attached to the same carbon which has hydroxyl group also. 1,1-diphenylethanol is a benzene substituted alcohol compound.


In this tutorial, we learn followings with preparing of 1,1-diphenylethanol.



Derive 1,1-diphenylethanol from benzene using Grignard reagents

Like aliphatic ethanol, we can prepare aromatic alcohols. Here we try to make benzene substituted alcohol compound using grignard reagent. In this example IUPAC name is given, then you have to draw the structure of molecule. We can understand, this compound is an alcohol because IUPAC name ends with ol part. Two benzene molecules are bonded to same carbon atom as substitutes (1,1-diphenyl). The root chain has two carbon atoms (eth). Also 1,1-diphenylethanol can be named as 1-Diphenyle-ethane-1-ol.



1,1-diphenylethanol structure

According to the IUPAC nomenclature, two phenyl groups are connected to the number one carbon atom of main chain. In the main chian, there are two carbon atoms with alcohol group. The carbon atom which hold the -OH group, takes the number one.

1,1-diphenylethanol | 1,1-diphenyl-ethane-1-ol

Prepare 1,1-diphenylethanol from benzene and ethanol

You can start your conversion from benzene and ethanol. Each step of benzene to 1,1-diphenylethanol is explained below.



Preparing chlorobenzene

Chlorobenzene is prepared by the reaction of benzene and chlorine gas ( Cl2 ) in the presence of anhydrous AlCl3.

This reaction is an electrophilic substitution reaction.


Chlorobenzene and magnesium, dry ether reaction | Grignard preparing

Next, chlorobenzene reacts with magnesium in dry dry ether medium and give grignard reagent (phenyl magnesium chloride) .


Ethanol to ethanoic acid

Ethanol is oxidized to ethanoic acid by strong oxidizing agent such as acidic potassium permanganate ( H+ / KMnO4 ). When oxidizing reaction is occurred purple colour of acidic potassium permanganate is reduced or become colourless because MnO4- is reduced to Mn2+.


Ethanoic acid to ethanoyl chloride

Ethanoic acid (a carboxylic acid) reacts with PCl3 or PCl5 to give ethanoyl chloride. Ethanoyl chloride is a carboxylic acid chloride compound.



Grignard reagent and carboxylic acid chloride reaction

When carboxylic acid chloride compound is treated with excess grignard reagent, two alkyl groups (in the grignard reagent) are added to the carboxylic acid chloride and forms tertiary alcohol when water is added.


Why excess grignard reagent?

It's required to substitute two alkyl groups from grignard reagent to carboxylic acid chloride to form tertiary alcohol. Therefore we have to add excess grignard reagent.



Phenyl magnesium chloride (grignard reagent) and ethanoyl chloride reaction

Finally grignard reagent and ethanoyl chloride are mixed together and add water. Two phenyl groups are added to the ethanoyl chloride molecule. It gives 1-diphenylethanol which is a tertiary alcohol.


Benzene to 1,1-diphenylethanol

benzene to 1,1-diphenylethanol


Acidity of 1,1-diphenylethanol

1,1-diphenylethanol is an tertiary alcohol. Acidity of 1,1-diphenylethanol is less than ethanol.

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