Extraction of Trimyristin Flashcards
What is Extraction?
A method for purification or separation based upon differences in solubility
Solid-Liquid Extraction
A technique that separates components in a solid mixture by dissolving certain component/s in a liquid solvent (one that doesn’t dissolve entire mixture; exhibits selective dissolution)
–> Separates components in a mixture into a liquid phase + a solid phase; separates SOLUBLE from INSOLUBLE
“crude material is partitioned between a liquid (solvent) and
solid phase.”
Liquid-Liquid Extraction
Components of a mixture get separated into two IMMISCIBLE liquid phases
(one phase is typically an aqueous solution and the other is usually an organic hydrophobic solution)
–> Think about the lipid extraction you did with Patricia!
What was being extracted from nutmeg?
We were extracting a natural compound, TRIMYRISTIN, from nutmeg (the source of the natural compound)
Dielectric Constant
= measure of polarity (higher the constant, the greater the polarity)
How does polarity relate to solubility?
“Like dissolves like”
(Solutes with similar intermolecular forces to a solvent will dissolve better)
Polarity of hydrocarbons (not substituted)
LOW polarity
Dielectric constant ~ 2
Polarity of Aliphatics/Aromatics (rings)
LOW polarity
Dielectric constant ~ 2
Polarity of Ethers
Ether = R-O-R
SLIGHTLY POLAR (Dielectric constant ~ 4)
–> Due to dipole interactions
Polarity of Esters
Ester = RCOO
–> Contains a double bonded oxygen
SLIGHTLY Polar (Dielectric constant ~ 6)
–> Due to dipole interactions and presence of a double bond
How does presence of a double bond impact polarity?
Presence of a double bond increases polarity due to the greater electron density concentrated between two atoms
(In general it involves more electrons which alters charge distribution)
–> ADDITIONALLY, presence of a double bond can provide opportunity for resonance which typically increases polarity due to the ability to distribute a charge over multiple bonds/atoms (> charge distribution = > dipole moment)
Polarity of Ketones
Ketones = RCOR
–> Contains double bonded oxygen
POLAR (Dielectric constant ~ 21)
–> Has strong dipole moment and presence of a double bond which both increase polarity
Polarity of Alcohols
Alcohol = ROH
POLAR (Dielectric constant ~ 24)
–> Has dipole interactions and hydrogen bonding
Factors impacting solubility
types of intermolecular forces that are similar/different between solute and solvent
1) Dipole moment (difference in EN) –> Polarity
2) Presence of double bonds (+ resonance)
3) Hydrogen Bonding
4) Ionic bonding
5) Length of carbon chain
How does the number of carbons present impact polarity?
As the length of a carbon chain increases, the overall polarity of a molecule decreases
–> Even if a molecule has a very polar functional group, if the carbon chain is long enough, it can essentially counteract the polarity of that group as the non-polar region is more extensive and the molecule takes on more of these non-polar characteristics
Composition of nutmeg
45-60% = Solid matter (insoluble in the solvent we’re using)
25-40% = nutmeg butter –> Where the trimyristin is found
5-15% = essential oils
What is trimyristin?
A triglyceride (tri-acyl glycerol)
–> Contains 3 polar groups attached to long carbon chains!
When initially extracting trimyristin from the nutmeg by dissolution, what else dissolves into the solvent used?
What dissolves in the solvent:
1) Nutmeg butter –> Trimyristin
2) Essential oils (= source of contamination for our purification of trimyristin!)
What solvent was utilized to extract trimyristin?
Diethyl Ether
Crude extract from dissolution of nutmeg in diethyl ether
= Trimyristin and all other soluble components (essential oils)
The crude (initial) extract is a MIXTURE!!!!!!!!
What was utilized to separate the insoluble versus soluble components of nutmeg?
1) Dissolution of soluble nutmeg components in DIETHYL ETHER
2) Gravity (hot) filtration of the nutmeg-ether mixture to remove insoluble components
Gravity Filtration setup of nutmeg-ether mixture
1) RBF clamped to a ring stand
2) STEMLESS funnel inserted into RBF
3) Fluted FLAST FLOW filter paper lining the funnel
4) Watch glass to cover the top of the funnel to prevent evaporation
What type of filter paper was utilized in the gravity filtration of the nutmeg-ether mixture?
Why?
Fast-flow filter paper
–> Used because it is more porous and thus allows sample to flow through more quickly
–> Important because we were dealing with a lot of solid so to avoid the liquid getting stuck due to clogging of the filter with the solid, the faster flow allows for more liquid to get through before a clog forms
Extraction of trimyristin: Gravity filtration
Why did we need to use a stemless funnel?
Because diethyl ether is constantly evaporating (very volatile)
–> As the solvent evaporates, the solution’s capacity to hold solute decreases which can lead to precipitation out of solution
By giving it more surface area to travel down (such as the stem of a funnel), the dissolved components may begin to precipitate out of solution as the solvent evaporates, causing you to lose sample to the stem of the funnel
–> Affects your yield!
What is the main issue working with diethyl ether?
How does this affect how the chemical is handled?
It has a low boiling point so it evaporates very very quickly
–> Flasks carrying diethyl ether should thus always be CORKED!!! Prevents the evaporation of it!
Rotary Evaporation
Technique to quickly and safely remove volatile compounds from non-volatile compounds (utilizing rotation and vacuum)
Evaporates out a liquid (solvent) leaving behind a solid product (solute) that you want to collect
What processes of rotary evaporation make it safer/faster?
Due to a few processes:
1) Application of vacuum: This accelerates rate of evaporation as it pulls vapors away from the liquid creating more “room” for more vapor to form
2) Rotation of the sample flask: Prevents “bumping” of the liquid (increases safety) and also increases rate of evaporation by exposing greater surface area of liquid to air = greater amount of evaporation
What is “bumping” of a liquid?
When a sample boils too quickly, causing sudden and vigorous release of vapor bubbles from a liquid
–> Safety hazard and possible source of sample loss
For rotary evaporation, how full can the RBF be?
Why?
No more than 1/2 full!!!!
Effect of vacuum on evaporation rate
A vacuum decreases atmospheric pressure which thus increases the amount of evaporation that can occur (increases evaporation rate)
–> Atmospheric pressure acts like a barrier preventing the vapor from easily leaving the liquid surface
(Think about it like trying to stand up from sitting on a chair but someone is sitting on top of you, it will be harder and take longer)
Purpose of the bumping trap in the rotovap
To trap any sample that may splash or spill out of the RBF due to bumping of the liquid
How does a rotovap work (overall)?
An RBF with your sample is attached the machine and then lowered into a water bath to promote boiling. Rotation of the RBF is started and vacuum is applied. This causes the liquid to evaporate and this vapor is sucked out of the RBF through a tube to get to a condenser filled with cold water. This causes the vapor to condense and then drop into a receiving flask, effectively separating the liquid from a solid in a mixture.
Why is rotary evaporation safer/chosen for this experiment?
1) Safer than boiling and distillation because it does not require heating –> Therefore it can work for more flammable liquids that pose a threat if heated
2) Minimizes risk of heating desired compound above the temperature at which it decomposes (prevents loss of desired product)
3) Safer waste disposal (liquid is trapped)
Once the trimyristin was extracted, how was it purified?
Through crystallization –> but NOT using hot filtration or vacuum filtration this time
What solvent was used for the recrystallization of trimyristin?
WHY?
ACETONE
This is because all the other impurities left behind with the crude trimyristin from the extraction process are all highly soluble in acetone but trimyristin is NOT (at room temp)
Recrystallization of Trimyristin with Acetone Process
Isolated the trimyristin using a pipette to aspirate out the supernatant (which contains the acetone and other impurities)
Process:
1) Put pipette tip flush against the bottom of the test tube
2) Begin to aspirate out the liquid by releasing the bulb
3) Repeat this process until all liquid is removed
How can we measure purity of a product (other than visually)?
Through melting point
Melting point supports assignment of…
1) Identity of a compound
2) PURITY of a compound!
Melting Point
Temperature at which a solid transforms into a liquid
Every molecule has its unique…
Melting point
How do you know if the observed melting point is close enough to the actual value to be able to identify a substance?
If the upper of lower limit of the melting point range is within 5 degrees celsius of the literature value (+/-), you can assign the substance the given identity
Melting point is measured as a…
RANGE
(On-set temp) - ( End MP)
On-set Temperature
The temperature at which there is the first appearance of liquid
End Melting Point Temperature
The temperature at which the entirety of the sample has changed to liquid (The temperature of the last appearance of the solute (solid)
As impurity increases, what happens to the melting point?
As impurity increases, the melting point BROADENS and DEPRESSES!!!!
Factors that influence melting point
1) Greater H-bonding = Higher MP
2) Ionic compounds have higher MP
3) Greater molecular weight = Higher MP –> Due to greater van der waals forces
4) Shape of molecules –> If the shape is such that they can pack together (in a lattice) better = Higher MP
How do you know if the observed melting point is of a pure solid?
The melting point temperature range should fall = or less than 2 degrees.
If range from onset temp to final temp is < or = 2 degrees, you have a pure compound
If the range is > 2 degrees then you CANNOT say that the product is pure!
Determining identity vs purity through melting point
Identity: Determined by comparing MP range observed to the literature value
Purity: Determined by examining the MP range.
Trimyristin: Has MP = 56-57 celsius, MW = 723.16 g/mol
You measured mp of 49–52 ºC. What conclusion can you make from this data?
A. The compound is trimyristin
B. The compound is pure
C. The compound is pure, and it is trimyristin
D. The compound is impure, and it is not trimyristin
E. The compound is pure, but it is not trimyristin
F. The compound is impure but it is likely trimyristin
F. The compound is impure but it is likely trimyristin
We can identify it as trimyristin because the upper limit of the MP is within 5 degrees of the literature value.
We CANNOT say that the product is pure as its MP range is over 3 degrees which is grater than 2!
