Draft:Traffic light reaction

• Comment: Breaks WP:NOTGUIDE Qcne (talk) 13:47, 5 December 2023 (UTC)

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== Introduction ==

The chemical traffic light reaction is a redox chemical reaction that induces a change in color. This involves an aqueous solution that includes glucose, sodium, hydroxide, and indigo carmine. In this experiment, an alkaline glucose solution is colored differently using an indicator called indigo carmine,. When an alkaline glucose solution is added to an indigo carmine solution, A color can turn yellow to red and then turn to green by shaking the solution, so it can easily reverse the reaction by shaking the solution. The oxygen in the air oxidizes the indigo carmine, causing the colors to shift in the opposite direction. Before experimenting make sure that professional supervision is taken care of the experimenter.

Yellow Red Green Colors

    In this reaction, the phenomenon of color changes of the traffic light reaction, during chemical reactions is quite fascinating. This transformation is primarily driven by the unique electronic properties of organic molecules. Most organic compounds, such as methanol, are colorless because they don’t have a conjugation within their molecular structures.

The key to understanding this color change lies in the concept of molecular conjugation, where the arrangement of alternating single and multiple bonds creates a system of overlapping pi orbitals. This extended pi-electron system results in a reduction of the energy gap between the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO). Consequently, the absorption band of the compound shifts from the ultraviolet (UV) region to the visible region of the electromagnetic spectrum.

When light interacts with a molecule, it can promote an electron from the HOMO to the LUMO. The energy required for this transition corresponds to a specific wavelength of light, which determines the color we perceive. Hence, the color of a compound is directly related to the energy of light it absorbs due to these electron transitions.

The change of traffic light reaction’s color due to the oxidation of indigo carmine in alcohol functional group and carbonyl group and the redox reaction back and forth during the observation.

     In the case of indigo carmine, during a chemical reaction, it undergoes changes in its functional groups that introduce conjugation or alter the existing conjugation within the molecule. These modifications result in the creation of derivative compounds with distinct absorption bands in the visible light range. As a result, indigo carmine can transition between different colors, such as yellow, green, and red, depending on the specific structural changes and the corresponding shifts in its absorption properties.

This ability to switch between different colors in response to chemical alterations highlights the intricate relationship between molecular structure and color in organic compounds, making the study of traffic light reactions a captivating area of research.

History

The initial discovery of this experiment is credited to Jonathan Atwood Campbell(scientist), and it gained further recognition through the work of Cook et al. The procedure involves a glass flask filled halfway with a transparent solution that transforms into a blue hue upon agitation. Allowing the mixture to settle results in the solution reverting to a colorless state. This cyclic sequence is repeatable. The solution, comprising sodium hydroxide, glucose, and methylene blue, is aqueous. The alkaline nature of the solution leads to colorlessness when left undisturbed, indicating the reduction of the dye by glucose. The act of shaking the flask reinstates the blue color, as atmospheric oxygen oxidizes the reduced form of methylene blue. The atmospheric oxygen penetrates the overall solution during this process.

Chemical structure

The chemical traffic light reaction contained 4 chemicals used namely glucose, sodium hydroxide (caustic soda), and indigo carmine, ascorbic acid(Vitamin C).

Glucose

The chemical formula for glucose is C6H12O6.  It is the monosaccharide that is most prevalent. Carbohydrate subcategories It is mostly produced by plants, mainly algae, during the process of photosynthesis, which uses energy from sunlight to combine carbon dioxide and water to form cellulose, the most common carbohydrate on Earth, which is found in their cell walls. An aldehyde group and six carbon atoms make up the monosaccharide glucose. It is an aldohexose as a result. Acyclic (open chains) and Cyclic(rings) are two possible forms of molecules.

Glucose Cyclic Form

Glucose Acyclic Form

Sodium Hydroxide

The chemical formula for sodium hydroxide is NaOH. It is a chemical that has strong base properties. Appearance white solid It may appear as flakes, pellets, or sheets. Sodium hydroxide is odorless but highly corrosive. It is also a substance that can absorb moisture effectively and causes heat when dissolved in water. If it encounters the skin, it may cause a burning sensation and severe burns.

Indigo Carmine

The chemical formula for indigo carmine is C16H8N2Na2O8S2. It's a dye that's been around for a while. The textile industry continues to use it extensively today. This substance is considered a hazardous substance. If it encounters skin, eyes, or ingestion can cause death to various body systems.

Indigo carmine chemical formula

Vitamin C

The chemical formula for vitamin C is C6H8O6. Vitamin C is found in certain fruits and vegetables and is important for our health. It dissolves in water easily and is well absorbed by our bodies. It has a long history of helping with a disease called scurvy and also helps with problems like bleeding gums.

Researchers have found that Vitamin C is important for many different processes in our bodies. One of its main jobs is to help make collagen, which is a protein that keeps our skin, muscles, and blood vessels healthy. It also helps wounds heal faster and helps our bodies absorb iron from the food we eat.

Vitamin C also acts like an antioxidant, which means it helps protect our cells from damage. This can help keep our skin looking young and prevent wrinkles. Vitamin C is used in various products like supplements, skin creams, and lotions because our bodies can't make it on their own, so we need to get it from the foods we eat.

Vitamin C chemical formula

Synthesis of Indigo carmine

Indigo Carmine is often produced synthetically through the fusion of N-phenylglycine in a mixture of sodamide, sodium, and potassium hydroxides under ammonia pressure, despite its potential derivation from the sulfonation of natural indigo. As a synthetic food color, it is identified chemically as disodium (2E)-3-oxo-2-(3-oxo-5-sulfonato-2,3-dihydro-1H-indol-2-ylidene)-2,3-dihydro-1H-indole-5-sulfonate. Authorized as a Group III color.

Synthesis of Glucose

Glucose has been artificially synthesized at the University of Würzburg, marking a significant achievement in understanding sugar constitution. This synthetic glucose, with the empirical formula C6H12O6, lacks the ability to rotate polarized light, distinguishing it from naturally occurring glucose varieties. Unlike its natural counterparts, it appears to produce a wholly inactive mixture, neutralizing both dextro and laevo forms.

Reaction of Chemical Traffic Light

The traffic light reaction is a fascinating demonstration in the field of chemistry, exemplifies the complexities and intricacies of chemical reaction rates and mechanisms. This experiment serves as a vivid illustration of how rates of individual sub-reactions and their interdependencies shape the outcome of complex chemical processes. Understanding these concepts requires delving into the nuances of how various reactions can occur simultaneously at different speeds and how factors such as reagent concentration and temperature can influence these rates.

In the realm of complex chemical reactions, it is not uncommon for multiple sub-reactions to take place concurrently, each progressing at its own unique rate. This variance in speed is critical, as it directly impacts the overall reaction rate. Typically, the quickest sub-reaction sets the pace for the entire process. However, in scenarios where intermediate molecules are formed and subsequently react to produce the final product, the slowest reaction becomes the rate-determining step. These intermediates are often present in low concentrations due to their high reactivity and tend to exist in a steady state. The equilibrium of a reaction is achieved when the rates of the forward and backward reactions are equal, and the overall reaction rate is a summation of the rates of all the steps in the mechanism, influenced by concentration and temperature. The traffic light reaction is a prime example of this principle, demonstrating how different reaction rates interact.

In the traffic light reaction, only three ingredients are needed: indigo carmine, sodium hydroxide and glucose. and water. Another formula consists of indigo carmine , ascorbic acid (Vitamin C), sodium bicarbonate, sodium chloride, copper(II) sulfate, sodium hydroxide and water. By doing so, chemical waste and the level of corrosive chemicals is reduced. The amount of solid chemicals dissolved in the experiment could be reduced from 60 grams to 6 grams. And the pH could be lowered from 13 to 3 which is easier to neutralize the pH to 7 by adding baking soda before disposal. Also, it is safer, and the reactions also occur faster and are easier to perform. These are combined in a flask, mixed, and sealed. Initially, at first, all chemicals are added together, and the color appears yellow. After shaking, the color turns green and then changes to red after it is left untouched. When further observed, the color turns back to yellow, which is why the solution is called the chemical traffic light. This reaction can be repeated many times, but it needs additional oxygen or indigo carmine.

This reaction occurs by oxidation and reduction of the solution where alkaline glucose solution is acting as a reducing agent. The glucose solution is added to the solution containing indicator (dye indigo carmine) the color changes occur. This reaction is also known as chemical clock experiment because concentrations of the products and reactants changed over the specific period. When the solution is shaken, oxygen dissolves in the solution and oxidizes indigo carmine. Solution becomes red if a small amount of oxygen is dissolved, and green if all indigo carmine is oxidized. The solution will turn back to original yellow color when the concentration of oxygen.

Procedure

First, to do the chemical traffic light reaction experimenter need to prepare all of these chemicals and chemical container, 2-3 grams of glucose, 2-3 grams of sodium hydroxide, 3-5 drops of Indigo carmine, 300-500 ml of distilled water or normal water, flask or water bottle. After preparing all of chemicals and chemical container experimenter can following the procedure step by step

1.     Add 2-3 grams each of glucose into the flask or water bottle.

2.     Add 2-3 grams of sodium hydroxide into the flask or water bottle.

3.    Add 300 ml of water into a flask then add 3 drops of an indigo carmine into the flask or water bottle.

4.    Shake the flask or water bottle 1-3 times carefully.

5.    Experimenter observe a color changing from yellow to red and green.

6.    Shake the flask or water bottle 1-3 times again.

7.    Experimenter observe a color changing back from green to red and yellow.

8.    This reaction can be repeated several times before the color fades.

After neutralizing the waste solution, it should be thoroughly cleaned out with lots of water and poured down the drain.