Experiment 9: The Aldol Condensation
Chris Chen*, Erica Chang, Work Station 4
Section 544, Green Lab, Department of Chemistry, Texas A&M University, College Station, TX, 77840 The sole purpose of performing the lab was to utilize aldol condensation reactions to synthesize a cyclopenta-dienone, while using UV spectrophotometry and computer visualization to further understand the dienone. In the beginning of the lab, the tetraphenylcyclopentadienone (TPCP) was synthesized using dibenzyl ketone and benzyl under extremely basic conditions. The synthesis process could be further understood by observing the mechanism portrayed in Figure 1. According to the figure, the dibenzyl ketone will first loose an alpha hydrogen to form the enolate intermediate.
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This is a contribution of the conjugated structure of the molecule that permits the absorption of the electromagnetic radiation in the visible spectrum of 400-700nm wavelength. In addition, the TPCP compound adopts a propeller shape in its three dimensional conformation. This can be described by the four phenyl rings are rotated out of the plane from the central ring due to the steric repulsion between the compounds. Lastly, after undergoing the synthesis process approximately 0.2 g of purified TPCP product was yielded. In other words, the theoretical yield was found to be 1.067 g, while the percent yield was determined to be 18.750%. (The calculations done to receive these digits could be found in the Calculations section of the article at the end of the article) The absorbance of the compound at 330 nm and 480 nm was predicted to be 1.1 and 0.2 respectively. Furthermore, the concentration of the TPCP using the equation displayed in the Calculations section at the end of the article was found to be 3.729*10-4 (330 nm) and 3.290*10-4 (480 nm). Some possible errors raised during the synthesis and spectrometric analysis of TPCP include the insufficient mixing of the hexane and TPCP, in which will result in the low absorbance of the compound. Additionally, the low yield is contributed from the loss of product during filtration.
Calculations
TY: 0.3 g (Benzil)* 1 mol (Benzil)/108.14 g (Benzil)*384.49
In a small reaction tube, the tetraphenylcyclopentadienone (0.110 g, 0.28 mmol) was added into the dimethyl acetylene dicarboxylate (0.1 mL) and nitrobenzene (1 mL) along with a boiling stick. The color of the mixed solution was purple. The solution was then heated to reflux until it turned into a tan color. After the color change has occurred, ethanol (3 mL) was stirred into the small reaction tube. After that, the small reaction tube was placed in an ice bath until the solid was formed at the bottom of the tube. Then, the solution with the precipitate was filtered through vacuum filtration and washed with ethanol. The precipitate then was dried and weighed. The final product was dimethyl tertraphenylpthalate (0.086 g, 0.172mmol, 61.42%).
This experiment was conduct to investigate the fluorescent behaviour of Leucophor PAF and to investigate the quenching of QBS with NaCl. It was found that the Leucophor PAF indeed satisfied the characteristic to act as whitening agent. It was also found that the quenching of QBS with NaCl was a diffusion-controlled collision process.
The goal of this two week lab was to examine the stereochemistry of the oxidation-reduction interconversion of 4-tert-butylcyclohexanol and 4-tert-butylcyclohexanone. The purpose of first week was to explore the oxidation of an alcohol to a ketone and see how the reduction of the ketone will affect the stereoselectivity. The purpose of first week is to oxidize the alcohol, 4-tert-butylcyclohexanol, to ketone just so that it can be reduced back into the alcohol to see how OH will react. The purpose of second week was to reduce 4-tert-butylcyclohexanol from first week and determine the effect of the product's diastereoselectivity by performing reduction procedures using sodium borohydride The chemicals for this lab are sodium hypochlorite, 4-tert-butylcyclohexanone
2-ethyl-1,3-hexanediol. The molecular weight of this compound is 146.2g/mol. It is converted into 2-ethyl-1-hydroxyhexan-3-one. This compounds molecular weight is 144.2g/mol. This gives a theoretical yield of .63 grams. My actual yield was .42 grams. Therefore, my percent yield was 67%. This was one of my highest yields yet. I felt that this was a good yield because part of this experiment is an equilibrium reaction. Hypochlorite must be used in excess to push the reaction to the right. Also, there were better ways to do this experiment where higher yields could have been produced. For example PCC could have been used. However, because of its toxic properties, its use is restricted. The purpose of this experiment was to determine which of the 3 compounds was formed from the starting material. The third compound was the oxidation of both alcohols. This could not have been my product because of the results of my IR. I had a broad large absorption is the range of 3200 to 3500 wavenumbers. This indicates the presence of an alcohol. If my compound had been fully oxidized then there would be no such alcohol present. Also, because of my IR, I know that my compound was one of the other 2 compounds because of the strong sharp absorption at 1705 wavenumbers. This indicates the presence of a carbonyl. Also, my 2,4-DNP test was positive. Therefore I had to prove which of the two compounds my final product was. The first was the oxidation of the primary alcohol, forming an aldehyde and a secondary alcohol. This could not have been my product because the Tollen’s test. My test was negative indicating no such aldehyde. Also, the textbook states that aldehydes show 2 characteristic absorption’s in the range of 2720-2820 wavenumbers. No such absorption’s were present in my sample. Therefore my final product was the oxidation of the secondary alcohol. My final product had a primary alcohol and a secondary ketone
...form 〖PbCrO〗_4 and then process it through a filter. After filtering the 〖PbCrO〗_4 I had to dry the 〖PbCrO〗_4 residue in the drying oven for 30 minutes at 80℃. Then let it cool for 5 minutes and weigh it and finally make a few calculations to obtain the theoretical, actual, and percent yields of 〖PbCrO〗_4. I was able to fulfill the experiment because I obtained all the answers to the equations in an accurate amount. I believe this experiment was a success due to my hypothesis of, If physical methods are used to separate 〖 PbCrO〗_4 precipitate from the reaction mixture then I can successfully calculate the theoretical, actual, and percent yields, being correct.
...teraction of the HOMO of the diene and the LUMO of the dienophile. This reaction was done at relatively low temperatures as the dry ether has a boiling point of 34.6 °C. At low temperature the endo preference predominates unless there is extreme steric hindrance, which in this case there is not. The endo product forms almost exclusively because of the activation barrier for endo being much lower than for exo. This means that the endo form is formed faster. When reactions proceed via the endo for the reaction is under kinetic control. Under kinetic control the adduct is more sterically congested, thus thermodynamically less stable. The endo form has a lower activation energy, however, the EXO form has a more stable product. As this is a symmetrical Diels-Alder reaction there is not two possible isomers of the product.
A weak peak was at a position between 1600-1620 cm-1 can also be seem in the IR, which was likely to be aromatic C=C functional group that was from two benzene rings attached to alkynes. On the other hand, the IR spectrum of the experimental diphenylacetylene resulted in 4 peaks. The first peak was strong and broad at the position of 3359.26 cm-1, which was most likely to be OH bond. The OH bond appeared in the spectrum because of the residue left from ethanol that was used to clean the product at the end of recrystallization process. It might also be from the water that was trapped in the crystal since the solution was put in ice bath during the recrystallization process. The second peak was weak, but sharp. It was at the position of 3062.93 cm-1, which indicated that C-H (sp2) was presence in the compound. The group was likely from the C-H bonds in the benzene ring attached to the alkyne. The remaining peaks were weak and at positions of 1637.48 and 1599.15 cm-1, respectively. This showed that the compound had aromatic C=C function groups, which was from the benzene rings. Overall, by looking at the functional groups presented in the compound, one can assume that the compound consisted of diphenylacetelene and ethanol or
It could have been lower than 100% because some product was lost during the recrystallization process, or due to an incorrect separation of the impurities when cooling the mixtures. The melting point data confirmed that the synthesized crystals were likely identical to the methoxybenzyl phenol ether because the mixed melting point was the same as the purified crystals. If the products were different or the synthesized product had to many impurities in it then the mixed melting point would have been lower than that of just the crystals, by themselves. The TLC made sense, after looking at the TLC plates under UV light and the calculation of the Rf values, it was confirmed that the 4- Methoxy-phenol was present in the unknown.
This excessive yield was resultant of the impurities within the product, where the solvents, particularly the dichloromethane, were not sufficiently removed from the product. In figure 3, the peak at 5.22 ppm with a normalised intensity of 1.00 evidenced the significant proportion of the dichloromethane in the product, and the peak at 0.88 ppm with a normalised intensity of 0.25 indicated some remaining hexane.4 The unreasonable yield was mostly attributed to these.
A spectrophotometer will be used in this experiment to measure the absorbance at a λmax of 430 nm. This wavelength will be used because it’s the wavelength absorbed by iodine, a yellow liquid that absorbs violet light and reflects yellow light. A 1 cm cuvette will be used to contain the reaction solutions, which will be put into the spectrophotometer to record absorbance. 3 mL plastic pipettes will be used to measure and add solutions to beakers and to the cuvette. While not very accurate, these pipettes will allow for quick and convenient transfer of solutions.
Cocamidopropyl Betaine is an ingredient synthesized from coconut milk most commonly found in cleaning solutions and appliances as a source of foam booster. Perhaps the most frequent use of Cocamidopropyl Betaine is shampoo, giving it the extreme capability to bubble and foam. Since many cleaning products result in the production of foam, they include Cocamidopropyl Betaine. More recent products have started to find alternative foaming compounds, but Cocamidopropyl Betaine still remains the most widely used source of foaming.
In the town of Seveso 25 km from Milan, the ICMESA factory (based on Swiss company Givaudan) was responsible for the manufacture of 2,4,5-trichlorophenol (TCP), a herbicide (Lees and Mannan, 2005). The reaction process normally required a time frame of approximately 14 hours (Sambeth, 1983). This process involves the alkaline hydrolysis of 1,2,4,5 – Tetrachlorobenzene in Ethyleneglycol solvent. Xylene is also added to the reaction mixture to remove any water that is produced. The sodium 2,4,5-trichlorophenate product is distilled to remove the solvents, acidified and purified by fractional distillation to produce TCP (Lees and Mannan, 2005).
Plontke, R. (2003, March 13). Chemnitz UT. TU Chemnitz: - Technische Universität Chemnitz. Retrieved April 1, 2014, from http://www.tu-chemnitz.de/en/
Langevin-Joliet, Hélène. "Chemistry International -- Newsmagazine for IUPAC." Chemistry International -- Newsmagazine for IUPAC. International Union of Pure and Applied Chemistry, 5 Jan. 2011. Web. 24 Oct. 2013. .
Determination by spectrophotometer: coordination compounds which can absorb light can be determined by this method.