a PLAYCHEM experiment
the first order decomposition of moneycules to loose change

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It has been reported that, under special conditions,  U.S. coins can interact to form moneycules , clusters of coins held together by greed.
Upon leaving the greed dominated domain, these moneycules revert to loose change.
The decomposition is a first order process.
In this experiment you will explore this first order decomposition.

First order kinetics....     
Log(C/Co)  =  -kt/2.30
1st order Half-Life ....    
t1/2  = -[Log(0.5)(2.303)]/k


Methylene Blue is a dye used in biological staining.  Its formula is on the left. Note the extended double bond structure which allows electronic absorption in the visible region. What color light is absorbed?
Note also the blue ionic structure is stabilized by allowing the + charge to be distributed on the two nitrogens attached to the ring system (to become partial "ammonium ions") as well as the ring sulfur.
When reduced, it forms "leucomethylene blue which is colorless.  The highest energy electrons are now more restricted in space.
In this experiment, glucose will be the reducing agent.
This  reaction takes place at a measurable rate.
Phenolphthalein is a common indicator.  It was also used as a laxative through almost all of the twentieth century.
Although it rapidly turns from colorless in acids to red in base, curiously it also slowly turns back to colorless at a measurable rate in very concentrated base.  

Note from the above formulas, the red color of phenolphthalein in weaker base which is caused by the absorption of mainly green light is supported by the extended conjugated double bond system.  However the reaction of a hydroxide ion with the phenolphthalein ion under very strongly basic conditions adds a HO group to one of these double bonds and significantly reduces the degree of "conjugation" (i.e. the highest energy electrons have become restricted to a smaller volume)
This means that the energy between the highest occupied orbital and the lowest vacant orbital increases and the molecule becomes colorless.  It takes more energy than is in any quantum of visible light (even blue) to cause this electronic transition.

RW Kluiber 4/1/2004