lab 3-quiz 2 Flashcards
why was anhydrous, not wet, diethyl either used in the preparation and reaction of the grignard reagent?
bc the reagent is very moisture sensitive. ether is an aprotic solvent, so the protonation of the reagent can be prevented. product: RMgX.
what would have been the product if wet diethyl ether was used?
alkane. R-H (butane?)+ Mg(OH)X
Why doesn’t the formation of the Grignard reagent start immediately upon addition of 1-bromobutane to the magnesium turnings? Why does the reaction proceed rapidly once it commences?
It took time to heat the magnesium. when reaction starts, heat is released in an exoteric reaction. This rapid release of heat causes the reaction to occur rapidly.
it is perfectly acceptable to use wet diethyl ether during the isolation of the product. why is it unnecessary to use anhydrous diethyl ether at this stage?
The product already formed after adding H3O+. Therefore, wet diethyl ether won’t affect product formation.
gas evolution frequently is observed during the separatory funnel extractions in this ex. what is the identity of this gas and how is it formed?
The gas is hydrogen gas: Mg + 2 HCl -> MgCl2 + H2
Why was potassium carbonate used in the distillation of 2-methyl-2-hexanol? Use the curved-arrow notation to draw a mechanism to show what likely would have occurred if the potassium carbonate was omitted
It was used to maintain alkalinity of the solution. if you heat it up, you can do an E2 elimination and form an alkene.
reagent
n-butylmagnesium bromide
product
2-methyl-2-hexanol
functions of hcl
protonates product and decomposes excess magnesium.
if one drop of water gets in flask:
0.05 ml
0.05 ml—> 0.05gx (1mol/18g)= 0.0028 mol.
organic phase
ether plus product plus K2CO3
aqueous phase
H20, HCL, MgClBr
literature boiling point of product
140 degrees celcius
if final is 1.4113 and temp is 22.8 then
1.4113 - (2.8 x 0.00045)
