Final Lab Report - lab work PDF

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The unknown compound for the liquid was determined to be benzaldehyde, C7H8O. Through the solubility tests, it was determined that the compound was insoluble in H2O, 2.5 M NaOH, 1.5 M HCl, and H2SO4. Solubility of the two liquids was determined by observing whether the two layers mixed or not. For all the tests with the unknown compound, two noticeable layers were seen, in other words, the liquids were immiscible. For H2SO4, a pH test was used to determine whether the unknown compound might have been soluble and when tested, the solution was weakly basic. Chemical Equations:

The solubility tests narrowed down the choices to alkanes, alkyl halides, aromatic compounds, aryl halides, esters, aldehydes, alkenes, alcohols, and ketones which helped determine what types of functional groups to test for. However, halides were ruled out through the Beilstein test, in which produced no blue-green flame (indication for a halogen). Also, through the ignition test, there was an orange, smoky, ashy flame when burning the liquid which indicates a presence of an aromatic ring. Functional group tests were performed to further analyze the unknown compound. Chromic Acid Oxidation test was used to determine whether there was an alcohol in the compound. The test came out to be positive, indicated through a change of color from an orangered chromic acid to a blue-green suspension, which concluded that there was a primary or secondary alcohol. The chromic acid reacted with the unknown alcohol which yields an aldehyde and the chromic acid and sulfate react to form the green color. A Lucas test was then performed to see whether the alcohol was primary or secondary. Hydrochloric acid reacts with the alcohol which forms a layer, however, no layer was formed which means it was a primary alcohol. However, through IR, boiling point, and derivative testing, it was concluded that there was no alcohol but rather a transition state or a reaction under acidic condition with an aldehyde. This makes sense because if it was an aldehyde attached to an aromatic ring, the carbonyl oxygen attacks a hydrogen which forms a primary alcohol under acidic conditions. Oxidation of aldehydes with chromic acid was performed to determine whether an aldehyde was present. In 30-45 seconds, there was a blue-green suspension that appeared and this indicates a presence of an aromatic aldehyde. Aromaticity was tested through the reaction with aluminum chloride/chloroform. The color of the solution changed from a diluted yellow to an orange/red color. The orange/red color means that there was a benzene ring in the compound. This is due to the aromatic compounds coming in contact with a mixture of aluminum chloride and chloroform; also, it is due from Friedel-Crafts reactions, which produces resonance stabilized and colored products. With these conclusions from the functional group tests and solubility, this compound must contain an aromatic/benzene ring, aldehyde, and/or alcohol.

Chemical Equations:

An IR spectrum was obtained for the unknown liquid. Four peaks were found to be useful in the analysis of the unknown liquid. At 1653.41 cm-1, alkenyl C=C peak was found (16801620 cm-1). Also, at 3063.59 cm-1, C-H aromatic peak was found (3030 cm-1). With these two combined, it was determined that one of the functional group was a benzene/aromatic ring. Two peaks formed at 2818.90 and 2736.69 cm-1. These two peaks indicated that there was a C-H aldehyde. These two peaks are uniquely seen for C-H aldehydes and are called Fermi resonance. This is due to the frequency of the splitting C-H and C-H bending motion. At 1701.91 cm-1, C=O peak was found (1660-1770 cm-1). However, because the peak was at the lower end of the range, this indicated this carbonyl group was part of an alpha, beta-unsaturated aldehyde or aromatic ring. With these IR observations, there was no O-H group present which debunks the positive test for alcohol, which means the alcohol was formed through the reaction between an acid and an aldehyde. Through the previous tests and new information regarding the unknown compound, it was determined that the ring must have an aldehyde group attached. The derivative that was synthesized was 2,4-Dinitrophenylhydrazone (orange crystals formed immediately after adding drops of unknown compound into ethanol and 2,4dinitrophenylhydrazone). This derivative was synthesized because the melting points for other benzaldehydes were far enough to distinguish from each other. However, this derivative was also picked because recrystallization was not necessary, which meant product could not be loss, and only thorough washing was necessary. The melting point of the derivative was 235.1-238.8ºC, and the literature melting point fell within these ranges: 237ºC. The derivative melting point and the unknown compound’s boiling point, 173.2ºC, and other factors, lead to the conclusion that the unknown compound was benzaldehyde.

Chemical Equation:

The unknown compound for the white solid was determined to be 4-aminophenol, C6H7NO. When conducting the solubility test, a flow chart was used to narrow down the functional groups on the unknown compound. When the unknown compound reacted H2O, the unknown compound was insoluble. However, the pH of the solution was tested and it was weakly acidic (3-5). In NaOH solution, the compound was soluble. This lead to the testing of the compound in NaHCO3, which lead to insoluble results which meant narrowed the functional groups to most phenols. However, further solubility tests were done and the compound was tested with HCl which lead to soluble results and precipitate formed but then dissolved. The compound was then narrowed down to amides also. When the compound is soluble in the acids or bases, this means a byproduct may have been released and the acid/base with the unknown mixed and reacted with one another. Chemical Equations:

The ignition test and Beilstein test resulted in ashy, smoky, and orange flames. This indicated that the compound contained no halogens. Also, this indicated that there is a presence of an aromatic compound. With these conclusions and the conclusions from the solubility tests, a number of functional group tests were performed. To test whether there was a phenol within the compound, pyridine and ferric chloride was mixed with the unknown. This resulted in a redbrown precipitate, which concludes there is a phenol present. An alcohol functional group was tested for with the use of chromic acid (oxidation); this resulted in the solution turning from an orange-red color to an opaque blue-green precipitate. This indicated that there was either a primary or secondary alcohol in the compound. With this, another alcohol test, the Lucas test, was performed to further test the degree of the alcohol. The test concluded that a secondary alcohol was present in the compound because a second layer of alkyl chloride formation formed within 5-10 minutes. The next functional group test, ketone/aldehyde oxidation with chromic acid, tested whether there was an aldehyde or ketone in the compound. Because no blue-green precipitation formed, no ketone/aldehyde was present in the compound. An ester was tested for next through the hydroxamic test. There was no blue-red color in the solution, therefore no ester was present. The Hensberg test was performed to test for an amine/amide. This resulted in a precipitation which meant there was a reaction with the reagents. This concludes there was a primary or secondary amine in the compound. In conclusion, the unknown compound contains a secondary alcohol, or in this case with the other test conclusion combined, a phenol with an amine group.

Chemical Equation:

The HNMR spectra demonstrated that there were four different H’s in the compound. At around 3-4 ppm, there was a hydrogen that seemed to belong to a nitrogen and at around 5.5 ppm, there is a hydrogen that belonged to an oxygen. The reason why it was thought this was because through the functional group analysis and solubility, an OH and NH 2 group had to be present and by comparing the signaling and strength of the peaks, it was determined that the first peak had to be nitrogen’s hydrogen and the second peak had to be oxygen’s hydrogen. The other two peaks were determined by comparing oxygen and nitrogen’s strengths against these hydrogens and whether they will move further down the ppm scale. It was hard to distinguish between the two peaks but it was determined that the furthest left was the hydrogen next to oxygen. An IR spectra was also obtained for the solid. There was a peak at 3409.05 cm-1 which meant there was an amine present. The melting point of the compound was 182-184ºC. With this information and all the other information collected, it seemed that the compound was 4-aminophenol. To distinguish this compound from the other similar compounds, 3,5-dinitrobenzoate was synthesized as the derivative. This resulted in a solid that had a melting point of 177.9.1-178.3ºC compared to the literature melting point of 178ºC, which is very accurate. The other derivatives did not have melting points that matched up to this either....