Why must care be taken to have the reagents and apparatus completely dry when a Grignard reaction is performed? Support your answer with chemical equations.
Thanks in advance
2006-11-21 12:24:00 · 2 answers · asked by Dastfreadsv 2 in Science & Mathematics ➔ Chemistry
To prevent the prepared Grignard reagent from hydrolyzing before it has a chance to react.
The Grignard reagent is prepared with R-Br
R-Br + Mg --> R-MgBr
This is then usually reacted with a Carbonyl compound (C=O) and then hydrolyzed to the alcohol. If water is present then:
R-MgBr + H2O --> R-H + Mg+2 + Br-1 + (OH)-1
This can also be written as:
R-MgBr + H2O --> R-H + Mg(OH)Br
2006-11-24 03:05:35 · answer #1 · answered by Richard 7 · 70⤊ 1⤋
They react vigorously with compounds with 'active' hydrogens- OH, NH and others. That's why the solution must be dry.
Grignards react enthusiastically with all kinds of C=O bonds.
The 'carbanionic' R group attacks the electron-poor carbonyl carbon. This is a very useful reaction. For example: reaction with carbon dioxide:
Making a carboxylic acid from an alkyl bromide
2006-11-24 13:22:48 · answer #2 · answered by Grasshopper 5 · 0⤊ 0⤋