Question #db577

1 Answer
Jan 1, 2016

Here's what I got.


So, methylmagnesium bromide, #"CH"_3"MgBr"#, which is a Grignard reagent, will react with cyclohexanone, #("CH"_2)_5"CO"#, to produce 1-methylcyclohexanol, #"CH"_3"C"_6"H"_10"OH"#.

The reaction will also produce #"Mg"("OH")"Br"#, but, depending on which reaction conditions you use, you can represent this compound as ions.

Here's how the mechanism for this reaction looks like

As you know, the difference in electronegativity between carbon and oxygen results in a polar carbon - oxygen bond.

This means that the carbon attached to the oxygen via a double bond, i.e. the one belonging to the carbony group, will be electron deficient.

Grignard reagents act as nucleophiles and attack this electron-deficient carbon, adding across the #"C"="O"# double bond - this is actually known as an alkylation reaction.

Here's where you have a choice for the mechanism. The next step involves the hydrolysis of the intermediary product, which is called a Grignard salt, to form the desired alcohol.

You can do this in one of two ways

  • you can add water
  • you can add a dilute acid

I think that if you're interested in isolating the resulting alcohol, you should add a dilute acid. I'm not sure about the nature of this salt, by I think that the acid will react with #"Mg"("OH")"Br"# and convert it to ions.

#"Mg"("OH")"Br" + "H"_3"O"_text((aq])^(+) -> "Mg"_text((aq])^(2+) + "Br"_text((aq])^(-) + 2"H"_2"O"_text((l])#

I chose this option - the weak acid is represented by #"OH"_3^(+)# in the above mechanism diagram.