A TRANSITICE (oldiarog dons S $408.740 3112.93 145 4H bazz.ss 1.40 WEST NC 77 Carbon:13 NMR ANGE Carbon 13 NMR UNVERZEDS
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- A Transitice Oldiarog Dons S 408 740 3112 93 145 4h Bazz Ss 1 40 West Nc 77 Carbon 13 Nmr Ange Carbon 13 Nmr Unverzeds 1 (50.98 KiB) Viewed 13 times
- A Transitice Oldiarog Dons S 408 740 3112 93 145 4h Bazz Ss 1 40 West Nc 77 Carbon 13 Nmr Ange Carbon 13 Nmr Unverzeds 2 (81.39 KiB) Viewed 13 times
SPECTRAL PROBLEMS USING IR, PROTON & CARBON NMR Eighteen spectral problems are attached, and the compounds represented by these spectra cover the range of functional groups that are discussed in organic chemistry. The problems are arranged in random order. Based on the information provided, the student should be able to deduce the structure. A few comments are given here. Elemental Analysis, Molecular Weight, Molecular Formula On each page you will find the molecular formula (MF). You may also find the molecular weight (MW) and percent by weight of each element present. The % of all elements except oxygen is provided; if the percentages given don't total 100%, add them and subtract from 100%. The only part of this data you really need is the molecular formula. Infrared Spectra The spectra were determined as a film between salt plates for liquids, and the KBr pellet method was used for solids. Small, broad peaks in the 3100-3400 cm-¹may be due to traces of moisture and should be ignored. Proton NMR Spectra In most cases, the peak areas are provided above the respective peaks (e.g. 1H, 3H, etc.) are the proton ratios (that is, the empirical formula of protons). In some cases, there are integration traces that give the relative integrations of each peak. For the traces, the total height of all of the traces equals the area corresponding to the number of hydrogens in the formula weight. In each case, compare the total of the hydrogen ratios to the number of hydrogens provided in the molecular formula, and if these are different multiply the given proton ratios by a suitable whole number. The spectra of alcohols have been run so there is no coupling of the -OH proton with protons on adjacent carbons. Correct interpretation of the PMR spectra involves (1) showing which hydrogens cause each set of absorptions (the chemical shifts). (2) accounting for the splitting pattern (where possible), and (3) accounting for the number of each type of hydrogen (the peak areas.) Carbon-13 NMR Spectra For each molecule, a "proton decoupled" spectrum is provided, resulting in one peak for each carbon "type." Peaks due to carbon in the deuterochloroform (CDC13) have been diminished in size but still may be seen around 77 ppm; thus, they may be ignored. You do not have to assign the peaks (chemical shifts) to the carbons that cause them, but at least make sure the number of peaks corresponds to the number of carbons in the structure. Keep in mind that more than one equivalent carbon atoms produce one peak so the number of peaks may actually be less than the number of carbon atoms in the molecule. For some spectra, a DEPT-135 spectrum is given. In this spectrum, signals that are positive (above the baseline) may be either a CH or CH; (comparing what you see in the proton NMR and the DEPT will help you sort this out). Any negative signals (below the baseline) are for CH₂ groups and carbons with no directly attached hydrogens are not visible. The Goal Your job is to deduce the structure of the compounds based on the information provided by the spectra and the molecular formulas. Be certain that you structure is consistent with each spectra and the molecular formula.