Blue bottle, red bottle, and traffic light reaction

   This week I want to show three reversible color changing reaction, and they are blue bottle, red bottle, and traffic light reaction. They are often used on magic shows or to perform demonstration experiments. However, though it seems to be complex and the ingredient should be the magician’s secret, I will reveal the secret to you today.

In fact, the mechanisms behind these amazing experiments are similar and easy to understand. When the bottle is shaken vigorously, one species in the solution would be oxidized (氧化) by the oxygen dissolving into the solution, and the color would change due to the different color that oxidized species has form the original one. After we put it aside and wait for a while, we could observe the color gradually return to the initial one. That is because the oxidized species has been reduced by the reductant (還原劑), usually glucose, in the solution.

Here are some videos:

 blue bottle

 red bottle and blue bottle (they are combined to make purple bottle)

traffic light

 In the blue bottle reaction, the species being oxidized is methylene blue (亞甲藍); in the read bottle reaction, that would be resazurin (刃天青); in the traffic light reaction, that would be indigo carmine (靛胭脂). The indigo carmine has three oxidation states with different colors so the color depends on which level it has been oxidized. 

methylene blue:

resazurin:

                            colorless                                                                                       red

  

indigo carmine:

Reference:

1.http://ncsu.edu/project/chemistrydemos/Kinetics/Blue%20Bottle.pdf

2.https://en.wikipedia.org/wiki/Blue_bottle_(chemical_reaction)

3.http://case.ntu.edu.tw/magichem/blog/wp-content/uploads/2010/09/NTUCASEChemdemo_example.pdf

Molecular toy building blocks

    I would like to introduce some geometrically interesting compounds this week. I think they are interesting because they have all kinds of structure—whatever you can imagine. They are just like tiny toy building blocks in microscopic world.

    The compounds that I want to talk about is “Platonic hydrocarbon”(柏拉圖烴). There are five Platonic solids: tetrahedron (正四面體), cube(正六面體), octahedron (正八面體), dodecahedron (正十二面體), icosahedron (正二十面體). But acutally only tetrahedron, cube, and icosahedron have their counterparts in hydrocarbon (due to the nature of carbon in bonding¹), and they are tetrahedrane, cubane, and dodecahedrane respectly.²

tetrahedrane, cubane, and dodecahedrane

   

  

    Of course there are piles of derivatives (衍生物) of Platonic hydrocarbon.For example:

Octanitrocubane, which is very explosive thus can be used in bomb and fuel:

Pagodane, an isomer of dodecahedrane:

  

Prismane, an isomer of bezene:

Fullerene (C60), which we are more familiar with:

However, chemist synthesis these compounds not only for fun but to collect data of these molecules. Chemistry behind these odd molecules is different form that behind ordinary molecules since they usually suffered from huge angle strain and are quite unstable. The data help chemist to develop and improve the existing theories (such as theoretical chemistry, computational chemistry, molecular modeling… and so on) and move further in chemistry.  

What’s more, molecule structure has no boundary so there are more left for us to explore!

1.The nature of carbon in bonding is that it merely has four valence and the angle shouldn't deviated from 109.5 degree too much.

2.Actually, tetrahedrane has not been synthesized yet, but lots of its derivatives have been published and the theoretical calculation also supports its stablity.

Reference:

1.https://en.wikipedia.org/wiki/Platonic_hydrocarbon

2.http://sites.northwestern.edu/scheidt/files/2011/11/012004_Galliford_Pltsolids.pdf

3.https://www.scripps.edu/baran/images/grpmtgpdf/Shenvi_Jan_06.pdf

Elephant's toothpaste

This week, I would like to talk about a common classroom demonstration—elephant’s toothpaste. The reaction behind this experiment is quite simple. It’s just about the spontaneous decomposition of hydrogen peroxide (H₂O₂) and the equation is showed below:

Here is the “recipe”:

1. 100 mL 30% hydrogen peroxide

2. 2.5 g KI

3. 20 mL surfactant

4. 3 mL fod coloring (or watercolor) in any color you like

    Put these things all together in a cylinder or something is long and has an upward opening than there will be a amazing show like this:

           So… it’s obvious why it gets its name “elephant’s toothpaste” ~~

           I want to talk about the role of each agent now. Hydrogen peroxide, is the main reagent while potassium iodide (KI) serves as catalyst (催化劑) and can be replaced by yeast or ferric cation (Fe³⁺). The present of catalyst makes the reaction much faster. Surfactant is used to retain the oxygen produce by decompose and makes bubbles. Finally, the coloring is optional because they are merely used to make the experiment colorful XD

    Enjoy yourself with this easily-conducted experiment!

*Attention

1. The decomposition reaction is exothermic and will make the container quiet hot!

2. 30% hydrogen peroxide is a strong oxidant which may cause serious result, please handle it with care!

Reference:

1. http://pubs.acs.org/doi/pdf/10.1021/acs.jchemed.5b00037

2. https://en.wikipedia.org/wiki/Elephant_toothpaste

NanoPutian

    NanoPutian is a class of organic compounds that were synthesized by James Tour et al. for educational purpose in 2003. The word “NanoPutian” consists of “nano” and “putian”. “Nano” is a prefix means 1*10^-9, like we usually say "nanometer", "nanogram", and “nanotechnology”. “Putian” originated from the word “lilliputian”, which means a very little world and refers to a fictional nation in Gulliver’s Travels called “Lilliput”.

    Let’s see some examples of NanoPutian and you will definitely have a deeper insight into them.

This is NanoKid:

    What's more, there are various characters that only differ from their heads, and here are some examples*:

  
  These are polymer and dimer of NanoPutian:

    Though the research of NanoPutian may seen meaningless, what Professor J. Tour was trying to do is to introduce more young scientist and the public to the microscopic nano-world. Also, he demonstrated to us that organic chemistry had already been well-developed and can synthesize almost any structure we want. 

    But for me, I think he was conveying that “scientist should study what they are interested in”. After all, the interest is the biggest motivation putting forward a scientist on the way of research. Someday, I hope I can become a chemist and devoted myself into studying what interested me, too!

    The article must end, but I wish you can be inspired and develop a long-lasting interest in chemistry as I do!

*The wave-like bond in the picture means bond without certain configuration.

#The original paper may help you with more details about NanoPutian, and here is the link: http://chemistry.mdma.ch/hiveboard/picproxie_docs/000466038-anthropomorphic.molecules.art.pdf