Cyclodextrin

Researchers at Temple University's Water and Environmental Technology (WET) Center have been investigating the use of cyclodextrins in the treatment of waste water.
Cyclodextrins are made up of sugar molecules, bonded together to form a ring. An example of the structure of a cyclodextrin, alpha-cyclodextrin which is a 6-membered sugar ring, is shown below:

Cyclodextrins can be used in water treatment because they can bond to substances such as toxic organic compounds or heavy metals and hold them inside the ring structure. Owing to the many polar OH functional groups, cyclodextrins are water soluble, but the researchers have produced insoluble materials by coating a thin layer of cyclodextrin on sand, glass, silica and filter paper. Doing this allows the absorbent material to be collected, washed and re-used.

Reference:
Temple University (2013, September 24). New adsorbent is more effective and environmentally friendly for treating wastewater. ScienceDaily. Retrieved September 30, 2013, from http://www.sciencedaily.com­ /releases/2013/09/130924174152.htm

Further Reading
Carbohydrates: http://ausetute.com.au/members/sugars.html 
Functional Groups: http://ausetute.com.au/fungroup.html
Solubility: http://ausetute.com.au/intermof.html

Zeolites: http://ausetute.com.au/members/zeolites.html
Polymers: http://ausetute.com.au/members/polymers.html 

Suggested Study Questions:

1. What does the "cyclo" part of the name in cyclodextrin refer to?
2. Use the structure above to determine the molecular formula for alpha-cyclodextrin.
3. Use the molecular formula to determine the empirical formula for alpha-cyclodextrin.
4. Calculate the percentage composition of alpha-cyclodextrin.
5. Draw the structure of alpha-cyclodextrin and locate and identify the functional groups.
6. Use a diagram to explain how alpha-cyclodextrin dissolves in water.
7. Use a diagram to explain how alpha-cyclodextrin could be used to remove lead ions from water.
8. Draw the structure of alpha-cyclodextrin an clearly identify all 6 of the sugar molecules making up the structure. 
9. Activated carbon is commonly used to remove contaminants from water. What benefits do you think there might be in using cyclodextrin-derived absorbant materials instead of activated carbon? 

Why Use a Volumetric Flask?

In order to prepare an aqueous standard solution, you transfer the solute to a volumetric flask and then you add water "up to the mark", that is, until the bottom of the meniscus lies on the "mark" when viewed at eye-level. You can quickly convince yourself of the need to view the "mark" at eye-level just be preparing your standard solution as above and then changing the angle you view it from.
But what about this need to add water to the solute in this oddly-shaped vessel called a volumetric flask?
Why couldn't you just weigh out the solute into a beaker then add the required volume of water from a pipette?
Or, if the solute is a liquid or a solution, why not just pipette the required volume into a beaker then pipette the required volume of solvent into the same beaker?

So, why not try it?

Experiment (a) For solid solutes such as sodium chloride (table salt) or sucrose ("sugar") just pour the solid into a small DRY measuring cylinder until you have 5 mL for example. Pour this solid into a 100 mL measuring cylinder. Add 50 mL of water from a pipette (you will need to keep swirling the flask while you add the water). Record the volume of the final solution. Repeat the experiment using different volumes of solute and solvent.
Repeat this experiment using sand as the "solute" and water as the solvent.

Experiment (b)  For liquid solutes such as ethanol (ethyl alcohol) or acetone (propanone) use a pipette to place 50 mL of the solute into a 100 mL measuing cylinder then add 50 mL of water from a pipette and record the volume of the final solution. Repeat the experiment using different volumes of solute and solvent.
Repeat this experiment using vegetable oil as the "solute" and water as the solvent.

If a solute dissolves in a solvent, the volume of the final solution is not equal to the volume of the solute plus the volume of the solvent. Sometimes adding a solute to a solvent results in a solution with a volume less than that of the solvent + solute, and sometimes adding a solute to a solvent results in a solution with a volume greater than that of the solvent + solute. Right now, there are no good, general theories to explain this behaviour! But it is because of this that we use that oddly shaped piece of glassware called a volumetric flask when we make up a standard solution.

Acetylene by Accident

Before the discovery of acetylene, it could take 7 men 10 days to chip out a porthole on a steel ship.
With the invention of the oxy-acetylene torch, it took 1 man 12 minutes to cut out the same porthole!
The oxy-acetylene torch that revolutionised the building industry would never have been invented had it not been for a series of accidents which started in 1836......
......read more in the September 2013 issue of AUS-e-NEWS.

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