Laboratory Operations- liquid liquid extractions

what is solvent extraction

it is a process where a compound of interest present in a mixture is moved from one phase into another phase using an extraction solvent

what are characteristics of extraction solvents

they usually have low boiling points to allow them to be easily evaporated off to isolate the desired compound

what are the 2 main purposes of extraction in organic chemistry

to obtain and isolate a desired substance from a mixture of substances

as a method to purify an organic substance through the removal of impurities

What is the most commonly used technique in organic chemistry

liquid liquid extraction

what happens during liquid liquid extraction

two immiscible solvents are used. One is aqueous (usually water) and the other is the organic layer (dichloromethane or diethyl ether)

What must be needed for the desired substance to be extracted in liquid liquid extraction

it must be more soluble in one of the layers so that is can be transferred from one layer to the other where it can be isolated and drawn off

what tool is used for liquid liquid extraction

a separator funnel is used for it

why is diethyl ether advantageous

its advantageous because it has a low boiling point and can dissolve both polar and non-polar components, but is highly flammable

why is dichloromethane advantageous

it is advantageous because it is not flammable

what is dichloromethan denser than

it is denser than water which is denser than diethyl ether

what is extraction a particularly effective technique for

it is especially effective for separating organic compounds when one of the compounds in the mixture can be chemically converted into an ionic form

what would the ionic form be soluble in

it would be soluble in the aqueous layer and could be extracted into it

what is the benefit of the separatory funnel

it provides a secure environment where liquids can be mixed, pressure can be built up while shaking and then the stopcock can be opened to allow the lower layer of the liquid to be drained out. The top layer is poured from the top of the funnel

What position is closed for the stopcock

it is closed in the horizontal position

how long should venting be continued for

it should be continued until there is no audible hiss of escaping vapors when the stopcock is opened

what is supposed to be isolated in the preformed liquid liquid extraction

a mixture of equal parts of the neutral compound 1, 4 dimethoxybenze, benzoic acid, and 2-naphthol in a dichloromethane solution should be isolated through it

What type of acid is 1,4 dimethoxybenzene

it is a stronger acid compound

what type of acid is 2- naphthol

it is a weaker acid compound

what is the pKa of benzoic acid

its pKa is 4

what is the pKa of 2-naphthol

its pKa is 9.5

What type of compounds are more soluble in the organic layer

uncharges compounds are more soluble in it and not the aqueous layer

Where are all three compounds at the beginning of the extraction

they are all uncharged and located in the organic layer of dichloromethane

What is one method for extracting a compound

one method is to turn the neutral compound into a charged compound which will then move from the organic layer and preferentially dissolve in the aqueous layer to be extracted

what is the result of the first extraction

it will be benzoic acid using the weak base sodium bicarbonate (NaHCO3)

What does the removal of the proton from benzoic acid by the weak base lead to

it leads to the formation o f the charged salt, sodium benzoate

Where will sodium benzoate move to

it is in now charged, it will move from the organic layer to the aqueous later where it can be isolated and drawn off

What does the second extraction use to remove the protone from the weaker acid, 2-naphthol

It uses NaOH to remove it which produces a charged molecule which will move from the organic layer into the aqueous layer where it can be dissolved and the drawn off

After the 2 extractions what is the only compound left in the organic layer

only 1,4 dimethoxybenzene will be left

What happens to the 2 charged compounds after they are removed from the organic layer

they are then exposed to acidic conditions, like the addition of HCl, in order to return them back into neutral compounds

When are 2-naphthol and benzoic acid ready to be collected via vacuum filtration

they are ready to be collected by it once both the solutions are acidic

What needs to happen in order to isolate 1,4-dimethoxybenzene

the dichloromethane is distilled off in order to obtain the solid 1, 4 dimethoxybenzene