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งๆ 4 Identification of Unknown Organic Compounds Reading: For a quick video about the “Rule of…
งๆ 4 Identification of Unknown Organic Compounds Reading: For a quick video about the “Rule of 13” https://www.youtube.com/watch?v=2YNE7w Golo Introduction One of the most important tasks that chemists are faced with is the separation and identification of compounds from mixtures. Gratifyingly, chemists have multiple tools in the quest to identify unknown organic compounds, Infrared spectroscopy is useful for determining functional groups that may exist in a molecule. NMR spectroscopy tells information about the connectivity of C-H bonds, as well as the numbers of and chemical environments of both carbon and hydrogen (as well as many other NMR active nuclei, such as fluorine and phosphorus). Mass spectrometry is also a very powerful tool. Weakly lonizing methods such as MALDI ( matrix-assisted laser desorptive ionization) and ESI (electrospray lonization) give molecular ions (gives you the molecular weight of the molecule), while strongly ionizing methods such as El (electron impact) and CI (chemical impact) generate significant fragmentation, which can be used to determine pieces that can fall off of the molecule in the mass spectrometer. Background After years of study, you have recently finished your graduate degree, and have just accepted a position at a small liberal arts college. You show up the first day and look into your new lab, and see that there is one unlabeled container, The previous occupant has retired at the beginning of the summer, and is apparently somewhere in the middle of the Atlantic Ocean now enjoying retirement and coincidentally cannot be reached). You’re unsure whether or not the compound is useful, but thankfully the department you’re in has a GC-MS, NMR and IR spectrometer, and a number of Meltemps. Between these instruments and online resources, you’re confident that you can identify this unlabeled compound. Although there is no label, you know based on the previous professor’s research that the compounds are likely to be from one of the following classes of compounds: Alcohols and phenols, aldehydes and ketones, amines, or carboxylic acids, amides, and esters, You’ll be provided with MS, IR, melting point, boiling point and NMR data on Blackboard. Prelab Questions There are no prelab questions for this lab. Results and Discussion Make sure to analyze all relevant spectra (label all peaks as appropriate). Explain in detail how you have used your data to determine the identity of the unknown compound. You will be graded for the success of your interpretation of your results and the logical conclusions you make based on that interpretation Postlab There are no postlab questions.
‘H NMR triplet quartet singlet PPM
13C NMR | 45 40 35 30 25 20 15 10 5 o PPM El-MS: 73.1 MP = -50°C BP = 55.5°C
IR spectrum SciFinder 100 08 TRANSMITTANCE [%] 09 01 20 “4000” 3500 3000 2500 2000 2500 1000 500 WAVENUMBER [cm-1]
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