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Experiment 13: Electrophilic aromatic substitution
Electrophilic aromatic substitution lab
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Recommended: Experiment 13: Electrophilic aromatic substitution
Introduction: From the lab book (1), Experiment 12.2A discusses the nitration of methyl benzoate to give an example of an electrophilic aromatic substitution reaction. This is seen in this experiment as a hydrogen on methyl benzoate is replaced with a nitronium ion. To achieve this an acid-base reaction, sulfuric acid and nitric acid react to produce a nitronium ion, a hydronium ion, and 2 bisulfate ions as seen in Structure 1. The nitronium ion reacts with an aromatic ring forming a sigma complex, Structure 2; which further stabilizes generating an aromatic ring due to conjugation, Structure 3. The formation of an intermediate is not mandatory, however it appears to be an easier resonance stabilizing mechanism (2). The final products of this nitration of Methyl benzoate for this experiment can be seen in Structure 4. Structure 1: The Formation of a Nitronium Ion Structure 2: Reaction of the Nitronium Ion with the Aromatic Ring Structure 3: Sp3 – Hybridized Carbon Intermediate Further Stabilizing to form an Aromatic Ring Structure 4: Expected Final Products, Meta, Ortho, and Para conformations Results and Discussion: This experiment needed to be performed slowly so as to not produce a powerful explosive known as 2,4,6-trinitrotoluene also known as TNT. This meant that a cooled sulfuric and nitric acid solution was added dropwise (~0.05 ml,) every two and half minutes. Crystals recovered from suction filtration using a Hirsch funnel were rinsed with cold water and methanol to remove …show more content…
1H-NMR was conducted and did not show a strong singlet around 2.4, which would rule out Methyl 2-nitrobenzoate. The formation at 8.8 is seen in Methyl 3-nitrobenzoate, but not seen in Methyl 4-nitrobenzoate. Our 1H-NMR contained peaks from 7.2 to 8.8 and thus would suggest the major presence of Methyl 3-nitrobenzoate. The color and appearance of the resulting product was a beige crystalline
The purpose for this lab was to use aluminum from a soda can to form a chemical compound known as hydrated potassium aluminum sulfate. In the lab aluminum waste were dissolved in KOH or potassium sulfide to form a complex alum. The solution was then filtered through gravity filtration to remove any solid material. 25 mLs of sulfuric acid was then added while gently boiling the solution resulting in crystals forming after cooling in an ice bath. The product was then collected and filter through vacuum filtration. Lastly, crystals were collected and weighed on a scale.
The percent yield of products that was calculated for this reaction was about 81.2%, fairly less pure than the previous product but still decently pure. A carbon NMR and H NMR were produced and used to identify the inequivalent carbons and hydrogens of the product. There were 9 constitutionally inequivalent carbons and potentially 4,5, or 6 constitutionally inequivalent hydrogens. On the H NMR there are 5 peaks, but at a closer inspection of the product, it seems there is only 4 constitutionally inequivalent hydrogens because of the symmetry held by the product and of this H’s. However, expansion of the peaks around the aromatic region on the NMR show 3 peaks, which was suppose to be only 2 peaks. In between the peaks is a peak from the solvent, xylene, that was used, which may account to for this discrepancy in the NMR. Furthermore, the product may have not been fully dissolved or was contaminated, leading to distortion (a splitting) of the peaks. The 2 peaks further down the spectrum were distinguished from two H’s, HF and HE, based off of shielding affects. The HF was closer to the O, so it experienced more of an up field shift than HE. On the C NMR, there are 9 constitutionally inequivalent carbons. A CNMR Peak Position for Typical Functional Group table was consulted to assign the carbons to their corresponding peaks. The carbonyl carbon, C1, is the farthest up field, while the carbons on the benzene ring are in the 120-140 ppm region. The sp3 hybridized carbon, C2 and C3, are the lowest on the spectrum. This reaction verifies the statement, ”Measurements have shown that while naphthalene and benzene both are considered especially stable due to their aromaticity, benzene is significantly more stable than naphthalene.” As seen in the reaction, the benzene ring is left untouched and only the naphthalene is involved in the reaction with maleic
The complete experimental procedure is available in the General Chemistry Laboratory Manual for CSU Bakersfield, CHEM 213, pages 20-22, 24-25. Experimental data are recorded on the attached data pages.
The overall objective of this experiment was to perform a Wittig reaction from creating an ylide and mixing it with a carbonyl (C=O) compound, cinnamaldehyde. The completion of the reaction was confirmed ultimately from the initial TLC analysis. Since TLC separates the components of the spotted material, as long as the retention factor values were different for cinnamaldehyde, the starting reagent, and the product(s), it was evident that some of the reaction had gone to completion. However, as seen in Figure 3, there was some blurred area between the product spots. This indicated that there still existed some impurities, most likely the starting reagent, which was affecting the movement of the compounds through the solvent, petroleum
Purpose: The objective of lab four was to use the website Late Nite Labs to determine mole-to-mole relationships and empirical formulas in chemical reactions. Combining and/or heating various compounds, observing the reactions and then calculating the moles revealed the balanced chemical reactions.
The solution is then stirred with a glass rod and put to cool in an ice-water bath before the slow addition of 1.0 mL of concentrated sulfuric acid (H2SO4) into the cold mixture in order to prevent the transpiration of undesired side reactions. In a separate test tube, 1-2 mL of 3 M aqueous sodium hydroxide solution can also be placed in the ice bath for extraction later on. After the mixture of NaBr, H2SO4 and 2-phenylethanol has been cooled and mixed, a solid will form. At this point, the application of the method of reflux can commence in order to both increase the reaction rate and to prevent any liquids from being evaporated, due to constant application of heat. With the apparatus set up (in addition to making sure all joints are well sealed, excluding the condenser top), the vial can then be put out of the ice bath, and put to warm. With stirring, all of the solid will eventually dissolve, and with constant heating, the mixture will gently reflux at around 160 ºC (using thermometer in the metal block to confirm), where the biphasic reaction mixture can then vigorously be stirred (with certain
...Coauthor, ChemBioChem 2006, 7, 1-10; b) A. Author, B. Coauthor, Angew. Chem. 2006, 118, 1-5; Angew. Chem. Int. Ed. 2006, 45, 1-5.))
yield of the pure product was determined to be 95.42%. PURPOSE The purpose of this lab was to perform an electro-philic aromatic substitution and determine the identity of the major product. TLC was used to detect unreacted starting material or isomeric products present in the reaction mixture. RESULTS The theoretical yield of the m-nitrobenzoate was determined to be 4.59 grams.
We obtained a purified yield of 22% for a white, crystalline solid, which weighed 0.033 g. Then, we used deuterated-chloroform to dissolve a small amount of the reaction product for 1H NMR testing. Because we had a small amount of purified product, this required us to rotovap the 1H NMR solution so that we can reuse the remaining for IR testing as well. We added an extra IR test for isopropanol to help us analyze the IR results for the product. Melting point was measured with the plateau temperature set at 64°C, which is 5°C below biphenyl’s expected boiling point of 69°C (U.S. National Library of Medicine). The melting point for the greyish solid was determined to be 64°C.
Predictions may be made about the suitability of possible catalysts by assuming that the mechanism of catalysis consists of two stages, either of which can be first:
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.
The lab this week was the first step of a multi-step synthesis. The first part of the synthesis was to isolate benzoin from benzaldehyde through condensation. The product purity of the benzoin can be considered at best medium to low. The percent yield was very low at around 6%, which could have resulted from contamination leading to impurities in the product. Moreover, the IR spectrum of the product shows certain irregularities with the OH stretch at 3375.84 cm-1 and CH stretch for aromatics around 3000 cm-1. The CH stretch appears to have the most impurities since its peak size is diminished compared to regular and does not read a specific peak. However, the IR spectra were able to confirm the product formation of benzoin through the two functional peaks as well as the C=O stretch
Plontke, R. (2003, March 13). Chemnitz UT. TU Chemnitz: - Technische Universität Chemnitz. Retrieved April 1, 2014, from http://www.tu-chemnitz.de/en/
was well within the range of the observed melting point of 113.2 °C – 115.4 °C. The NMR and IR spectra were similar to the expected outcome and the predicted shifts and frequencies were very close to that of the experimental. In conclusion, the synthesis of acetanilide proved to be a success.
V. Amarnath, D. C. Anthony, K. Amarnath, W. M. Valentine, L. A. Wetterau, D. G. J. Org. Chem. 1991, 56, p. 6924-6931.