Nitration of Methylbenzoate Essay
Nitration of Methyl Benzoate Purpose: The purpose of this experiment was to synthesize methyl m-Nitrobenzoate from methyl benzoate, concentrated HNO3, and concentrated H2 SO4 by an electrophilic substitution reaction. The H2 SO4 and the HNO3 were initially combined to form nitronium ion which was then used as an electrophile in the reaction. Crystals that were collected after the formation of the methyl m-Nitrobenzoate were collected by vacuum filtration and the product was isolated and purified by recrystallization. Reaction scheme: Formation of Electrophile:
Procedure: The procedure was as is described in “Laboratory Manual for Organic Chemistry 2311”, Eighth Edition, Jane E.
Wissinger, Cengage Learning Custom Solutions, Mason, Ohio, 2010, pp. 74-76 Reagent Table: | Methyl Benzoate| H2 SO4| HNO3| Methyl m-nitrobenzoate| Mol. Wt (g/mol)| 136. 2| 98. 08| 63. 01| 181. 0| Mass (Grams)| 0. 5| -| -| 0. 67| Moles(mol)| 0. 0037| -| -| 0. 0037| Volume (ml)| 0. 5| 1. 35| 0. 35| -| Density (g/ml)| 1. 8| 1. 84| 1. 51| 1. 30| Melting point| -12. 6oC| 10OC| -42OC| 78OC| Solubility| Insoluble| Miscible | Soluble| -| Hazards| Irritant| Highly corrosive| Toxic| -| Literature: 1Chemspider 2Merck Index Observations and Results: The reaction turned yellowish when the acid mixture was added to the methyl benzoate.
The yellowish presence turned into white crystals when ice was added to the reaction. The crude product was obtained by vacuum filtration. It was then recrystallized to obtain the pure compound.
The recrystallized mass I obtained was greater than 50%. The melting point of the purified product ranged from 72oC- 75oC. 1H NMR, TLC, and IR spectroscopy was also used to analyze the purified methyl m-nitrobenzoate. Yield Table: Actual Yield (grams)| % Yield| Mpt. Range (oC)| Appearance | 0. 428g| 64%| 72-75| White powdery solid| Calculation for % yield: Theoretical yield0. 0037*181= 0. 6697g Mass of crude product 0. 686g Mass of crystalized product 0. 428g Purity Calculation: Purity calculation is not needed because the 1H NMR does not indicate the presence of the starting materials.
IR spectrum: Compound| Bond Vibration| Frequency (cm-1)| Intensity| Methyl m-nitrobenzoate| C=O (Stretch)| 1730. 0| Moderate| | (Stretch)| 1290| Strong| | (Stretch)| 2955. 3| Strong| | C=C (aromatic)| 1618. 5| Strong| | NO2 (Stretch)| 1535. 1| moderate| 1HNMR spectrum of compound: Protons, HX| Chemical Shift, ppm| Splitting Pattern, n| J value, Hz| Integration value, cm| Relative # H’s| Ha| 7. 65| Triplet | 7. 8| 2. 4| 1| Hb| 8. 4| Multiplet | -| 3. 8| 1| Hc| 8. 4| Multiplet| -| 3. 8| 1| Hd| 8. 9| Triplet| 1. 6| 1. 5| 1| He| 4. 0| Singlet| -| 7. 3| 3| J-value: (7. 709-7. 70)*200= 7. 8 Hz TLC results: Compound| Height of 20% ethyl acetate/hexane| Heights of Compound| Rf Values| Methyl Benzoate| 5. 3| 4. 5| 0. 85| Crude| 5. 3| 3. 1| 0. 58| Purified| 5. 3| 3. 4| 0. 64| Conclusion/Discussion: In this experiment, we synthesize methyl m-nitrobenzoate by an electrophilic substitution reaction. The mass of the crude product ended up being higher than the maximum expected mass, 0. 6697g. This might have been due to inaccurate measurement of one of the starting materials. When compared to the literature IR of methyl m-nitrobenzoate (chemicalbook. om), the experimental IR appears to be valid. This is because the interested peaks are shown to be in its expected positions. The 2955. 5 peak indicates the presence of C-H bond stretch of sp2. The 1730 peak indicates the C=O. The 1535. 1 indicates NO2 stretch. The TLC analyzed the polarity between methyl benzoate, crude methyl-3-nitrobenzoate, and purified methyl-3-nitrobenzoate. The solvent that was used was 20% ethyl acetate/hexane. Methyl benzoate had a higher Rf value than the nitro benzoate indicating that methyl benzoate had low polarity.
Since the crude and pure product had close but not the same Rf values, it indicates that the crude product contained a lot of the pure product before the recrystallization took place. In addition, the 1H NMR indicated that the product was methyl-3-nitrobenzoate. The obtained 1H NMR corresponds to the literature 1H NMR (pg. 76 of manual). The number of peaks shows how many different H atoms are present in the product. The splitting patterns confirmed the positions of the H-atoms. There two peaks, ~1. 6 and 7. 2, indicates the presence of the water and CDCI3 respectively.
However, the water only showed up at a very small concentration which indicates that there was very little water present in the results. The triplet at ~7. 65 indicates that the split occurred between two H- atoms should have been seen as a multiplet but rather appeared as a triplet. This was because the J-value was too close to one another and therefore appeared as a triplet. The multiplet at 8. 4 indicates two types of H atoms with close J values and appears as doublets. Its appearance as a triplet indicates that it might have been split by only one H atom instead of two H atoms.
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