When it comes to the Dental Admission Test, there are a lot of things that you need to prepare for. For instance, you need to be ready for organic chemistry questions that can cover different topics. Here we aim to get you ready for one particular subject that might come up on the organic chemistry section of the DAT. These are organic chemistry lab techniques that you need to know.
Knowing about different methods of organic chemistry lab techniques is fundamental. Students often confuse the terms and definitions. With a little help from us, we’ll make sure that this is not the case for you.
Below you will find a list of organic chemistry lab techniques as well as their definitions. Make sure to read slowly and understand each of them.
Organic Chemistry lab techniques.
Below is a list from purification methods and extraction to chromatography and electrophoresis.
Purification methods.
Extraction: It’s used to separate dissolved substances. This is done considering different solubility in aqueous vs organic solvents.
Filtration: This method is used to separate solids from liquids.
Recrystallization: It’s used to separate solid based on different solubilities. For this method of purification, the temperature of the substances is very important.
Sublimation: Separates solids based on their ability to sublime.
Centrifugation: This method is used to separate large “things”, like cells, organelles, macromolecules and more, based on their masses and densities.
Distillation: It’s used to separate liquids based on their boiling points. This method depends on intermolecular forces to act.
Chromatography: This method uses stationary and mobile phases to separate compounds based on how tightly they adhere. This is generally due to polarity or size depending on the substance.
Electrophoresis: It’s used to separate biological macromolecules like proteins or nuclei acids, based on their sizes and charge.
Now that we have cleared up a bit of what each method means let’s take a deeper look into each one. Beginning from the top of the list and adding a few extra methods as go move along. Below we’ll focus more on the characteristics of each method and their key points. This is something you must know for the Dental Admission Test.
Extraction.
Water = aqueous layer; ether = organic layer.
Like dissolves like.
3 IMF that affects solubility.
Hydrogen bonding – For example. Alcohols and acids will move into the aqueous layer.
Dipole-Dipole interactions – less likely to move in the aqueous layer.
Van der Waals, also known as London dispersion = nonpolar molecules, does not go into the aqueous layer.
When acid dissociates resulting anion formed is more soluble.
Adding a base does help extract acid into the aqueous layer.
Simple Distillation.
Separate liquids that boil below 150°C and are at least 25°C apart. In their boiling points.
Vacuum distillation.
Separates liquids that boil above 150°C.
Reduced Pressure, lowering the BP of liquids and thus preventing their decomposition typical at high temperatures.
Fractional distillation.
Separates liquids that have boiling points that are at least 25°C apart from each other.
Near the top of the column, the vapor is composed solely of 1 component, which will then condense and collect in the receiving flask.
It can be thought of as a repeated distillation of the same vapor.
Thin-layer chromatography.
Used to isolate individual compounds from a complex mixture.
Stationary phase, solid medium, and mobile phase, liquid.
Different compounds will adhere to a stationary phase with different 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 – a very nonpolar stationary phase instead of silica gel.
Electrophoresis.
Separates macromolecules based on isoelectric point.
If pH = Isoelectric point then protein doesn’t move.
If pH > isoelectric point then protein is deprotonated.
SDS & Agarose gel electrophoresis.
Separates molecules based on size.
MP and BP trends.
BP:
Increase 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.
Final Thoughts.
With the brief list above and all the most important points and characteristics of the purification methods, you’re one step closer to mastering all that you need to know to ace the organic chemistry section of the DAT.
Remember that there are a lot of other questions that you need to prepare for. There are a lot of topics and sections you need to cover and read over. If you don’t know where to start then we suggest that make a list of each section of the DAT.
Furthermore, if you need to find help preparing and want to use a test prep service then feel free to test out datprep. This is one of the best services on the market and will make sure you score higher on Dental Admission Test.
