Identification of Unknown Compound using 13C NMR

Identification of Unknown Compound using 13C NMRIdentification of Unknown Compound 15 using 13C NMR and IR Spectra paired with Melting Point AnalysisAbstractGiven an undiagnosed fuse, infrargond (IR) spectrum analysis disregard be apply to determine the functional groups that make up the compound. This can be supplemented with 13C NMR spectroscopy and melting commove analysis to determine the identity of the strange compound. After completion of the analysis methods, it was determined that the identity of the unbeknown(predicate) compound (unknown 15) is p-Methylaniline (p-Toluidine), C7H9N (Figure 1).Introduction Infrared (IR) spectroscopy is extensively used instrumental proficiency in organic chemistry.It is the measurement of the wavelength and intensity of the absorption of mid-infrared fairylike by a sample. Mid-infrared is energetic enough to excite molecular vibrations to higher energy levels. The wavelength of infrared absorption bands is characteristic of specifi c types of chemical bonds, and infrared spectroscopy finds its greatest utility for identification of functional groups within organic molecules (1). An infrared spectrophotometer is an instrument that passes infrared light through an organic molecule and produces a spectrum that contains a plot of the amount of light transmitted on the vertical axis against the wavelength of infrared radiation on the horizontal axis. In infrared spectra the absorption peaks point downward because the vertical axis is the percentage transmittance of the radiation through the sample (2).Nuclear magnetic resonance spectroscopy (NMR) can be used to complement IR spectroscopy. While IR can determine functional groups, NMR can determine the molecular structure. Finding the melting point of the unknown can help to determine the purity of the compound.ResultsIR DataFunctional GroupMolecular MotionObserved Wavenumber (cm-1)Literature Value guide1-3 (cm-1)Peak bulkPeak ShapeN-HStretch3333.853335WeakSharpC- HStretch2914.732780WeakSharpC=CStretch1621.281600-1430MediumSharpC-HBending(in plane)1274.331275-1000Medium assign13C NMR DataAtomAtom GroupPeak Observed (ppm)Peak Calculated (ppm)1C-N1441442 and 6CH one hundred fifteen115.23 and 5CH130129.604C=C127126.77CH32121.26Melting Point DataObserved Melting Point Range (C)Literature Melting Point Range4 (C)Trial 144-4744-45Trial 2 44-45DiscussionThe IR analysis of the unknown compound 15 determined that it consists of a benzene ring, amino and methyl groups. According to the referred literature (3) values of 3335-3400 range for stretches are evident which indicates primary amines. The spectrum shows primary amines stretch at 3333.85 Next can be noticed that CH stretches from the benzene ring occur at 3014.65 and 2914.73. C=C stretches are known to occur at the 1600-1430 according to literature, and in this spectra are illustrated at 1621.28 At 1274.33C-H bend is evident. This spectrum correlates well with literature values which confirms s uccessful identification of p-methylaniline.The melting point analysis was used to determine the purity of the unknown sample. The literature values for p-methylaniline range from 44-45C (4) and the observed melting point values were 44-47C for trial 1 and 44-45C for trial 2. The trial 1 has a higher melting point compare to the literature values. This could be due to the amount of sample placed in the capillary tubes as well as the purity of the sample (4). Because trial 1 has such a large range, the sample may not be pure.The results from the 13C NMR showed that compound contained summetry. deuce peaks of the same height were observed at about 115 and 130ppm and two other peaks at 144 and 127ppm. According to the literature values aromatic carbons expect between 120-160ppm (3), which helped to determine that this compound contains a benzene ring. It was noted as well that one other peak appeared much further downfield at 21ppm. Using an NMR predictor, the peaks for p-methylanilin e were calculated to be 144, 115.2, 129.60, 126.7 and 21.26 ppm, which match the observed peaks.ConclusionAfter performing IR spectroscopy, melting point and 13C NMR analysis, it was found that unknown compound 15 is p-methylaniline. P-methylaniline contains a benzene ring, methyl and amine groups in a p- position. Based on slight deviations in the melting point, the sample could give birth some impurities. An error could be improper loading of the sample in the capillary tube. So to avoid this chemical error, a better laboratory technique could be used.ReferencesIR SpectroscopyMohrig J.R. et al. Techniques in Organic Chemistry 2nd Ed.2. Skoog, D. A., Principles of Instrumental Analysis, 3rd EdStawikowski, M. Experiment 2 Identification of unknown compound based on IR spectroscopy, melting point analysis and supplemental 13C NMR spectroscopy data BlackBoardSmiley RA (2000). Ullmanns Encyclopedia of Industrial Chemistry. magic trick Wiley and Sons.