Absorption Spectra of Conjugated Dyes

The unknown sample was identified to contain Acetaminophen, Aspirin, and caffeine based on comparison of known Rf values (Table 1). When comparing the traveled UV lit spots (figure 1), Aspirin and Ibuprofen traveled the same distance from the start line. Unknown sample 16 contains Aspirin not Ibuprofen, due to the intensity of the spot under UV light. Aspirin and the unknown shared that same intensity, whereas Ibuprofen did not share that same strength of brightness. The distance traveled by the samples was dependent upon their affinity for the mobile phase 200:1 ethyl acetate – acetic acid. The samples that traveled the furthest like the Aspirin and Ibuprofen were the most soluble in the mobile phase. The samples that traveled the shortest

In experiment two, the drug Panacetin was separated by a series of chemical reactions into its three components: sucrose, aspirin, and an unknown active ingredient, either acetanilide or phenacetin. The purpose of this lab was to determine what percentages of each component is present in the pain-killer. The initial step was to dissolve Panacetin in dichloromethane. However, sucrose is insoluble in dichloromethane because organic molecules are soluble in organic solvents, and dichloromethane is an inorganic solvent, so only aspirin and the unknown dissolved. By using gravity filtration, sucrose was filtered from the solution and 0.30g of solid was collected.

After placing in darkness the colorless solution resulted by reformation of the radical intermediates to a new thermodynamic product via C-N bond at room temperature. UV-Vis was conducted on the solution before and after the irradiation with sunlight: UVtoluene 554.92nm, A=0.12 before irradiation and A=1.05 after. The peak at 554.92nm corresponds to yellow/green light and its complementary colour is red/violet. This validates the solutions violet color. The increased absorbance was accounted for an increase in the radical component. The radical was formed when exposed to light, which was visually apparent with the purple coloration and proved the thermodynamic dimer was also photochromic. When dimer 4 is exposed to light photons collide with the molecule and impart energy upon them. This energy is significant enough to break the bond between the two rings and results

The concentrations and absorbances of the red and blue dyes were used to find the concentration of the purple dyes. From the graph of the blue dye, the linear equation for absorbance was y = mx + b. From that formula came the equation y = 7.915 x 104 (x) + 0.02489, where y represents absorbance, m is slope, x is concentration/molarity, and b is the constant/y-intercept. The same set up was performed for the red dye, but the equation produced was y = 1.045 x 104 (x) +.001298. The equations found when graphing absorbance vs. concentration were used to find the concentration of the purple dyes. The absorbance for purple dye 3 on the red wavelength of 470 nm equaled 0.149 and 0.818 for the blue wavelength of 635 nm. For purple dye 1

From this graph and chart we can see that the higher the concentration the higher the absorbance, all the different concentrations were tested at the same wavelength (625nm). Also we can determine our unknown substances concentration by using the absorbance we got for it. The red dot on the graph followed by the line towards the horizontal axis indicates that the concentration of fast green was 34% or 5.1x10-3.

Samples of benzophenone, malonic acid, and biphenyl were each tested with water, methyl alcohol, and hexane. Benzophenone was insoluble in water as it is nonpolar while water is highly polar. Benzophenone was soluble in methyl alcohol, dissolving in 15 seconds, because methyl alcohol is intermediately polar as benzophenone is nonpolar. Methyl alcohol is polar but not as much as water. Thus, the nonpolar benzophenone was soluble in methyl alcohol. Benzophenone was partially soluble in hexane because hexane is nonpolar as is benzophenone. Thus, benzophenone was dissolved in hexane. Malonic acid was soluble in water because both malonic acid and water are polar. It took 25 seconds for malonic acid to dissolve in water. Malonic acid was soluble in methyl alcohol because malonic acid is polar and methyl alcohol is intermediately polar, allowing malonic acid to dissolve in the methanol in 15 seconds. Malonic acid was insoluble in hexane because hexane is nonpolar while malonic acid is polar. Biphenyl was insoluble in water as water is highly polar whilst biphenyl is nonpolar. Biphenyl was partially soluble in methanol which is intermediately polar whilst biphenyl is nonpolar, allowing it to dissolve a little. Biphenyl was soluble in hexane because both biphenyl and hexane are nonpolar molecules. Biphenyl dissolved in hexane in 10 seconds.

Figure 2: Dye percents versus absorbance in a control, 10%, 20%, and 30% azide solutions.

In this experiment, 0.31 g (2.87 mmol) of 2-methylphenol was suspended in a 10 mL Erlenmeyer flask along with 1 mL of water and a stir bar. The flask was clamped onto a hotplate/stirrer and turned on so that the stir bar would turn freely. Based on the amount of 2-methylphenol, 0.957 mL (0.00287 mmol) NaOH was calculated and collected in a syringe. The NaOH was then added to the 2-methylphenol solution and allowed to mix completely. In another 10 mL Erlenmeyer flask, 0.34 g (2.92 mmol) of sodium chloroacetate was calculated based on the amount of 2-methylphenol and placed into the flask along with 1 mL of water. The sodium chloroacetate solution was mixed until dissolved. The sodium chloroacetate solution was poured into the 2-methylphenol and NaOH solution after it was fully dissolved using a microscale funnel.

The dyes in the laboratory experiment are made of numerous colors, mainly red and blue, the spectra from each of the dyes corresponded to the wavelengths obtained from each of dye i.e. 620 nm for red and 450 nm for blue.

In this paper, an artificial food dye will be made to mimic the color of Full Throttle. To determine what food dye are needed, Full Throttle will be put through a spectrometer to determine what wavelengths are absorbed. Specific wavelengths absorbed will correspond to specific colors absorbed. It was determined that yellow 5 and yellow 6 will be used to make our artificial food dye to mimic Full Throttle. Using Beer’s Law, it was determined that a concentration of 0.0000236 moles of Yellow 5 and a concentration of 0.0001494 moles of yellow 6. Using our line of best fit from the absorption graphs, it was determined

The absorbance is measured using a Plate reader and a Standard curve is generated. Also, the different types of pipetting techniques are assessed in this Assay.

During the separation of the pigments by chromatography paper, chlorophyll b traveled the shortest distance, chlorophyll a went above it, and the highest went beta carotene. This

This entry was posted in Research papers and tagged UV Spectroscopy research paper, UV Spectroscopy research proposal on May 19, 2013.

The highly conjugated system of the cyanine dyes makes it a very good compound in the development of more efficient solar cells. In this experiment, the maximum wavelength was measured for nine dyes using a UV-Vis spectrum. The result that were obtained agreed with Kuhn’s model for the less polarizable end groups such as 3,3 '-diethyloxadicarbocyanine and 3,3 '-diethyloxatricarbocyanine. That suggested that these two compounds were not as easy to polarize compared to the rest of the dyes. The rest of the dyes required the use of the empirical parameter α to provide more reliable predictions of the wavelengths. This was due to the highly polarized ends of the dyes which needed the adjustment of the parameter to get more accurate results. The series with the higher polarizable end groups’ absorbed higher wavelength light than the less polarized groups. This supported the idea of the one-dimensional box. Also, higher wavelength was determined to be associated with longer conjugated carbon methine chains between the Nitrogen atoms. Kuhn’s free electron model was very reliable for this system.

Before any calculations, the spectra from the HCl solution and NaOH solution was verified to make sure that the wavelength at which the deprotonated form of 2-naphthol absorbs at 345 nm and that protonated form does not absorb significantly at the same wavelength. All the spectra in Figure 1 were baseline-corrected using the HCl solution spectrum, shown in Figure 2, and the NaOH solution spectrum was used to determine Amax at 345 nm.