Solvatochromic Dye: Exploring UV-Vis, IR, and NMR SpectroscopyPre LabIntroductionIn this lab, the ultimate goal is the determination of seven unknown solvents by collecting data from a spectrophotometer. The other main goals of this experiment are to obtain UV-Vis spectral data using a diode array of a spectrophotometer, analyze providedInfrared (IR) spectra for seven unknown organic molecules, analyze provided 1H nuclear magnetic resonance (NMR) spectra for seven unknown organic solvents, and use solvametric properties of Brooker’s merocyanine to rank the polarities of seven unknown solvents using spectral data1. A possible detailed list of the solvents that will be determined can be found in the table of reagents. The main concept of this lab is spectroscopy. This is using a light to probe the molecular structure of a sample. There are different types of spectroscopy that will be utilized in thislab. The first type is UV-Vis Spectroscopy. This type of spectroscopy introduces light to asample over a ranger of wavelengths1. The percentage of light transmitted can be seen in the following equation-log(%T/100) = Abs (1)%T is the transmittance and Abs is the absorbance. The absorbance vs. wavelength can beplotted and lambda max can be seen in this area. This is not very useful in determining unknown solutions, therefore Brooker’s merocyanine to determine these solutions. This merocyanine is an organic complex molecule that is soluble in many different solvents1. This is very sensitive to changes in polarity. These color changes can then be observed and data can be gathered about solvatochromism. This is when a compound shows a significant change in absorption when a solvent is dissolved1. Absorbance of light can also be correlated to energy of transition. The transition energy can be given by the following equationET = hcNA/ λmax(2)λmax is the max wavelength absorbed, h is Planck’s constant, c is the speed of light and Na is Avagadros constant.. Also the transition energy for an electron can be varied making the max lambda vary. This is most stable for a nonpolar solvent and will be smallest for this type of solvent. Also a Zwitterion is a molecule whose ionic charges add to give overall neutrality. With Brooker’s solution, the energy of transition In a polar solvent is less than nonpolar. This is the definition of “blue shift” or “Hypsochromic Shift”. 2The next kind of spectroscopy is Infrared. Infrared is when a sample is irradiated with light over a range of frequencies and absorbance’s in the infrared electromagnetic spectrum1. The absorbance is measured by a correspondence of a certain frequency with avibrational mode of the molecule. A vibrational mode of energy can be described as the simple harmonic oscillations of atoms about the equilibrium position of a bond in the x, y, z plane. These vibration modes correspond to a certain frequency. The photons are absorbed and the molecule begins to vibrate.. The frequencies of these are reported in wave numbers which can be given by the following equationWave numbers = ν / cWhere “ν” is the frequency and “c” is the speed of light. These will give rise to absorbance bands. The final kind of spectroscopy used is nuclear magnetic resonance (NMR) spectroscopy. This can be found by observing the 1H molecule or the probe structural information of the 13C molecule. For a 1H molecule they have an overall positive charge creating a magnetic field. When they are put into a magnetic field they all have about the same direction as the external NMR signal. An NMR signal is a measure of how the external field changes the moment vectors relative to the field1. Shielding can also occur in protons which is when other atoms block magnetic field from these atoms. The more shielding or deshielding (when protons are near other highly electronegative atoms) that is shown can be assigned upfield or down field in the spectrum. The location is known as the shift or ∂. This is given by parts per million for a peak on a spectrum. A proton in a nucleus will display (N+1) peaks in its signal. N is the number of nuclei affected by the signal. This can be used to determine how many hydrogen atoms are in a molecule.These chemistry concepts and the concept of spectroscopy can be seen in chemistry in the real world. Spectroscopy dyes were used in in the detection of biodiesel in diesel. The Solvatochromic dye was used in order for the direct simple detection2. This is used in several industries. Also this kind of process was used to detect low concentration of organiccompounds3. Finally this type of spectroscopy can show intramolecular charge transitions showing emission through the visible spectrum in many different types of experiments4. 3Table of ReagentsReagent Molar Mass(g/mol)Density(g/mL)Hazards Polarity Index(P’)H2O 18.02 1.00 Dangerous in copious amounts10.2Acetone 58.08 .791 Flammable, Harmful if swallowed, skin, eye irritant5.1Methanol 32.04 .791 Flammable, skin, eye irritant 5.1Absolute Ethanol 46.07 .789 Flammable, skin and severe eye irritant. Explosive vapors5.21-Propanal 65.10 .803 Flammable, skin and severeeye irritant. 4.02-Propanal 60.10 .786 Flammable, skin and severe eye irritant. 4.0Chloroform 119.38 1.48 Extremely dangerous if inhaled. Skin and eye irritant4.1Acetonitrile 41.05 .786 Flammable, skin and severe eye irritant. 5.8Dimethyl Sulfoxide 78.13 1.10 Dangerous in large amounts 7.2Ethyl Acetate 88.11 .897 Flammable, skin and eye irritant. 4.4DMF 73.09 .944 Explosive liquid and poisonous gases when burned6.4Brooker’s merocyanine 211.26 1.268 Irritant, Harmful if swallowedN/AProcedure1. A detailed procedure is in the lab manual1.2. Obtain solutions in large test tubes and label them A-G with the correct solution in each test tube3. Add Brooker’s merocyanine and rank solutions based on polarity by looking at the color of each.4. Prepare the solutions for a UV-Vis spectrophotometer.a. Label seven cuvettes A-G b. Using a Pasteur pipet, fill the cuvettes to the corresponding test tube. c. Handle the cuvettes on the frosted side.45. Using the spectrophotometer, determine the λmax of each solution. Take the spectra from 400 nm to 700 nm6. Record λmax and the absorbance at this wavelength for each solution.7. From the results calculate ET8. Make a data with the solvent, visible color, λmax and transition energy9. Now rank the solvents in order of increasing polarity10. Analyze IR spectrum for each