Separation Techniques Flashcards
Extraction goal:
- phase of reactants
-
Goal: to separate aqueous mixtures
- partition compound between two liquid phase
Phase 1: polar aqeous
Phase 2: Nonpolar organic
Dichloromethane, chloroform, diethyl ether, ethyl ester
Types of organic solvents in extraction
Aqueous phase of extraction and why?
Water, highly polar, immisible in organic solvents
What phase settles to the bottom in extraction?
More dense phase, usually aqueous water
Can you separate neutral molecule with uncharged acidic and basic components?
Yes with the addition of base, you can deprotonate the acid or addition of acid, you can protonate the base
- this changed substance will be dissolved and extracted in aqueous layer
Can you separate molecule with two similar components, say two uncharged acids?
Yes, if one acid is stronger than the other it will be deprotonated faster
- weak base can deprotonate stronger acid (negatively charged) extracted in aqueous layer
What is the uncertainty with distillation?
- even before a molecule reaches its boiling point, some of the liquid is turning into gas
- thus not sure that the lower BP molecule is fully distilling first
What is the process of overcoming uncertainty in distillation?
Multiple distillation procedures to remove impurities
What is the min level of BP difference ion simple distillation?
25 C or more
What does fractional distillation due?
- fractionated column makes it harder for vapor molecules to travel all the way up and decondense
- can separate two molecule with closer BP
Phases of chromatography:
Mobile: liquid or gas phase
Stationary phase
TLC is what
Thin layer chromatography:
Stationary: adsorbant silica polar gel (can H-bond)
Mobile: non-polar solvent, hexane (elluent)
How do types of molecules move within TLC?
Non-polar move faster and farther with solvent up apparatus
Polar: move solar and less far due to bonding with aparatus
Column chromatography phases:
Stationary phase: solid adsorbent at bottom of column
Sample of interest added
Mobile phase: solvent, poured through column pushing sample
How are sizes eluded in size exclusion chrom?
Largest pass through more easily then small and then smallest
Ion exchange chrom defintions:
Cation and Anion traps what and what is the stationary phase:
Cation exchange traps cations
- stationary is anion:
Anion exchange traps anions
- stationary is cation:
Affinity chromatography, what happens to the compound of interest?
Ligands make up stationary phase:
- compound of interest binds to ligands on the sides of column
- uninterested items pass through
How do you get the compound of interest elluted from affinity chrom?
- Cause bound compound of interest to dissociate
- useful for proteins, bio macro molecules
Gas chromotography phases:
Gas-liquid
Mobile phase: gas like N or He
Interest phase: vaporized
Stationary phase: liquid or polymer coating
What does ellutants of gas-liquid chromotography say?
Each peak is a different compound, width/area is amount of compound
- smaller (lower BP) are sooner, earlier peaks
What is difference of HPLC?
High performance liquid chromotography
Mobile phase: liquid flows through
Stationary phase: solid
Distinguishable: extremely high pressures to move solvent through column compared to gravity in regular column
- improve interaction of stationary phase with solutes floating (can use smaller solutes)
- can help with greater separation of solutes
How do molecules move through HPLC vs revere phase HPLC?
- non polar move faster and farther due to interaction with mobile phase
- polar molecules move slower due to increased interactions with stationary phase
Reverse phase: non polar stationary (hydrocarbon chains)
- polar mobile phase and polar molecules move faster
What is important factor to consider in recrystallizaitons?
Solvent of choice:
- Desired product soluble at high temp, insoluble at low temp
What is the initiation step of recrystallization?
- Nucleation via seed crystal initiates process
- Scratch side of flask, rough seed helps form
- usu repeat multiple times to reduce impurities
What is last step of recrystallization?
Filtration of liquid solid mixture, left with desired product
What is the most successful method for extracting methanal from aqueous solution?
Serial extractions are more effective than single extraction
- answer choices with volume amounts comparable, most successive extractions is best
