Organic Chemistry Lab DAT Notes
Organic Chemistry Laboratory DAT Review Notes
The Organic Chemistry Lab DAT Notes word document are located here: Organic Chemistry Lab Notes
Summary of Purification Methods
| Method | Use |
| Extraction | Separates dissolved subs. Based on differential solubility in aqueous vs. organic solvents |
| Filtration | separates solids from liquids |
| Recrystallization | Separates solids based on diff. solubilities; temperature is important |
| Sublimation | Separates solids based on their ability to sublime |
| Centrifugation | Separates large things (ex. Cells, organelles, macromolecules) based on mass and density |
| Distillation | Separates liquids based on boiling point (depends on intermolecular forces) |
| Chromatography | Uses stationary and mobile phases to separate compounds based on how tightly they adhere (generally due to polarity, but sometimes size as well) |
| Electrophoresis | Used to separate biological macromolecules (such as proteins or nucleic acids) based on size and sometimes charge |
Extraction
- Water = aqueous layer; ether = organic layer
- Like dissolves like
- 3 IMF that affects solubility
- hydrogen bonding – ex. Alcohols & acids will move into aq. layer
- dipole-dipole interactions – less likely to move in aq. layer
- van der Waals (London dispersion) = nonpolar molecules (does not go into aq. layer)
- when ACID dissociates, resulting anion formed is more soluble
- ***ADDing a BASE helps EXTRACT ACID into the aq. layer
Simple Distillation
- separate liquids that boil BELOW 150OC (at least 25C apart)
Vacuum Distillation
- separates liquids that boil ABOVE 150C
- reduced P, lowering the BP of liquids (preventing their decomposition typical at high T)
Fractional Distillation
- separates liquids that boil LESS than 25C apart
- near the top of the column, vapor is composed solely of 1 component, which will condense and collect in the receiving flask
- can be thought of as repeated distillation of same vapor
Thin Layer Chromotography
- used to isolate individual compounds from a complex mixture
- stationary phase (solid medium) & mobile phase (liquid)
- diff. compounds will adhere to stationary phase w/ diff. strengths
- POLAR compounds bound TIGHTly to the silica gel – eluting poorly into the less polar solvent
- Rf = dist. compound / dist. of solvent
- Reverse phase chromatography – very nonpolar stationary phase instead of silica gel
Electrophoresis
- Separates macromolecules based on isolectric point
- If pH = isoelectric point protein doesn’t move
- If pH > isoelectric point protein deprotonated
SDS & Agorose Gel Electrophoresis
- Separates molecules based on SIZE
MP and BP trends
Bp:
-increases with chain length due to dispersion forces
-decreases with branching
MP:
-increases with branching because the molecules can pack tightly
-increases with chain length again due to dispersion forces
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