Grignard Flashcards
What is the purpose of Grignard
nucleophillic addition of a Grignard reagent to carbonyl groups to make a C-C bond
what are the key features of a Grignard reaction
-grignard reagent prepared from an lkyl halide
- reaction is sensitive to moisture
- CO2 forms carboxylic acid derivatives
how do esters react with grignard
they react with two equivalents of grignard
What can a substrate not have for a grignard?
it cannot have an acidic group attached to it (OH or NH2) because an acid base reaction will occur
what types of substrates will undergo single additions of grignard
aldehydes and CO2
what types of substrates will undergo acid base chemistry rather than nucleophillic addition
carboxylic acids and any OH or NH2 on the molecule
what are the characteristics of a Grignard reagent
nucleophilic and basic
Why do we do an acidic wash after reacting a Grignard with CO2
it protonates the oxygen to form a carboxylic acid
what substrates will undergo a double addition of grignard
esters
what are grignards made from
alkyl bromides
what would happen if you tried to make a grignard from a substrate with a ketone on it?
it would form an intramolecular reaction
draw out the possible byproducts
what is wurtz couling? When does this occur
it is a byproduct where the grignard reagent reacts with the alkyl halide
it occurs when there is too much of the alkyl halide available at once
how do we separate our final product
we use a separatory funnel with a basic wash to deprotonate it and make the compound water soluble
what are the steps to initiation
add 5-10% of the alkyl halide until it becomes cloudy and warm, then add the rest of the alkyl halide
what can we use to initiate the reaction
catalyst and heat
why must we keep the concentration of the alkyl halide initially low
to avoid qurtz coupling
how to we prepare our glassware
flame dry everything from bottom to top
what catalysts do we use for the reaction
I2 or dibromoethane
why is the initiation step heterogeneous with ether and magnesium
magnesium does not dissolve in the reaction
what keeps the reflux going in the reaction
the exothermicity
when are out of plane bends not seen on an IR?
when there is an electron-withdrawing group present that is para to the substituent
