Early Approaches and Recent Theories An attempt to explain the indigo formation by this method is in Gattermann´s “Preparative Organic Chemistry”. However, until now there is no a complete and correct theoretical treatment of the involved steps in this synthesis, nor comments on the reaction mechanisms.įigure 1. In fact, from only two reactants, a reaction series occurs. Introduction The Baeyer-Drewsen synthesis of indigo, from o-nitrobenzaldehyde and acetone, in alkaline medium, is an outstanding synthesis in Organic Chemistry. Repeat the experiment using leaves from different trees so you can compare the pigments, just as you compared different brands and colors of markers.1. Check back periodically for about 90 minutes and write down your observations. Make sure the end of the paper towel is barely touching the green alcohol.ĩ. Remove the plastic wrap from the cup and place the pencil over the mouth of the cup so that the paper towel is dangling inside the glass. Just as you did in the marker experiment, cut a strip of paper towel the same height as the clear cup and tape the end of the paper towel to the pencil.Ĩ. It may take about 30 minutes for the alcohol to turn green.ħ. Wait for the alcohol to absorb the leaf pigments. Place the covered clear cup in the pan full of hot tap water.Ħ. Fill the shallow pan with hot tap water.ĥ. Cover the top of the clear cup with plastic wrap.Ĥ. Pour enough rubbing alcohol into the cup to cover the leaf pieces.ģ. Tear the green leaf into tiny pieces and drop the pieces into the clear cup.Ģ. Shallow pan (a brownie pan would work well)ġ. Green leaves (make sure they haven’t changed colors and aren’t too dry)ġ0. Use chromatography to separate the pigments and find their “true” colors.ġ. You can even use chromatography to predict the colors that leaves will change in the fall! Just like black markers have more than one color, leaves have more than one pigment. Compare the Rf and range of colors to identify the mystery mark! Next, go through the same process with all three markers. Now, it’s your job to solve which marker your friend used! First, go through the chromatography process (above) with the mystery mark. Have a friend select one of the three black markers and draw a line on a strip of paper towel, just as you did before. Try using different colors and compare the results! Each component may have slightly different properties, which is what allows them to flow at different rates or travel varying distances from the original starting point. The spread of the water helps separate the different components that make up the mixture. Because of cohesion within liquid molecules, and adhesion between the liquid and the solid, capillary action allows liquids to move against the forces of gravity. The solvent (mobile) travels through the paper (stationary) using capillary action.Ĭapillary Action is what causes the water to “climb” up your paper. In paper chromatography, the stationary phase is a strip of paper, and the mobile phase is a solvent. There are four different types of chromatography, but today, we will be focusing on paper chromatography. The stationary phase is the component that DOES NOT move, and the mobile phase is the component that DOES move. The separation is completed by passing the mixture through a solution using a medium.Ĭhromatography includes a stationary phase and a mobile phase. Another example of separating a mixture using chromatography would be separating common table salt, NaCl, into Sodium (Na) and Chlorine (Cl). For example, investigators sometimes use chromatography to identify unknown substances at crimes scenes. Why would we want to separate components of a material in the first place? Chromatography allows us to view the individual parts of a mixture, thus making it easier to analyze. Chromatography allows us to separate those substances. Sometimes a mixture appears homogenous, but is actually made up of several different substances. Chromatography is the separation of a material into its individual components.
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