NMR spectrum of ethanol

Figure 18.16 One-dlmenslonal NMR spectra, (a) H-NMR spectrum of ethanol. The NMR signals (chemical shifts) for all the hydrogen atoms In this small molecule are clearly separated from each other. In this spectrum the signal from the CH3 protons Is split Into three peaks and that from the CH2 protons Into four peaks close to each other, due to the experimental conditions, (b) H-NMR spectrum of a small protein, the C-terminal domain of a cellulase, comprising 36 amino acid residues. The NMR signals from many individual hydrogen atoms overlap and peaks are obtained that comprise signals from many hydrogen atoms. (Courtesy of Per Kraulis, Uppsala, from data published in Kraulis et al.. Biochemistry 28 7241-7257, 1989.)...

FIGURE I The NMR spectrum of ethanol. The red letters denote the protons that give rise to the associated peaks. 

Figure 2.39 NMR spectrum of ethanol (CH3 CH2 OH). The three peaks are due to the three groups in the compound, which can be split into multiple peaks using a higher resolution. The peak at zero chemical shift is due to the reference compound, DSS.

The different types (doublet, triplet, and so on) exhibit a characteristic ratio of intensities. Doublets are equally intense. Triplets have a more intense central peak flanked by two equal peaks of lesser intensity. A quartet has two equally intense central peaks with two smaller outer peaks that are equal to each other in intensity. See Figure 5-4 for the NMR spectrum of ethanol. 

When the NMR spectrum of ethanol is examined under higher resolution than in Fig. 8.2, each of the three lines is found to be split into a, number of closely spaced lines (Fig. 8.10). Unlike chemical shifts, these splittings are independent of the applied field B0. They are due to neigh-... 

Figure 9-23 Proton nmr spectrum of ethanol (containing a trace of hydrochloric acid). Chemical shifts are relative to tetramethylsilane (CH3)4Si, that is, TMS = 0.00 ppm. The stepped line is an integral of the areas under each of the resonance lines.

The first direct NMR spectroscopic evidence for the existence of primary alkylox-onium ions (protonated alcohols) in superacid solutions was found in 1961 by MacLean and Mackor.50 The NMR spectrum of ethanol in HF-BF3 solution at —70°C gave a well-resolved triplet at about 81 H 9.90 for the protons on oxygen coupled to the methylene protons. In HS03F this fine structure is not observed, even at 95°C, due to the fast proton exchange.51... 

Chemical shifts can also vary within a molecule for instance, ethanol (CH3CH2OH) exhibits three proton NMR resonances and two 13C resonances. The lines in the proton NMR spectrum of ethanol are further split by spin-spin coupling ,/. When magnetic nuclei are close to each other in a molecule, the magnetic field at one nucleus is affected by the magnetic alignment of the others (see Fig. 3.5). Spin-spin coupling can reveal much detailed information about the relative positions of different nuclei in a molecule. 

NMR Spectrum of Ethanol. Figure 11.58 shows the H1 NMR spectrum of ethanol (after a drop of HC1 was added, which causes rapid spin exchange between hydroxyl protons of neighboring molecules, thus simplifying the spectrum). 

Figure 4.44. One-Dimensional NMR Spectra. (A) iR-NMR spectrum of ethanol (CH3CH2OH) shows that the...

A classic example of this effect is the proton NMR spectrum of ethanol CH3CH2OH, shown in Fig. 15.2. The three peaks, with intensity ratios 3 2 1, can be identified with the three chemically distinct environments in which the protons find themselves three methyl protons (CH3), two methylene protons (CH2) and one hydroxyl proton (OH). 

Figure 15.2 Oscilloscope trace showing the first NMR spectrum of ethanol, taken at Stanforil University in I951. (Courtesy of Varian, Inc.)...

Figure 15.4 High-resolution NMR spectrum of ethanol showing 5-scale of chemical shifts. The line at 5 = 0 corresponds to the TMS trace added as a reference.

Figure 3-49 One-dimensional NMR spectra. (A) H-NMR spectrum of ethanol (CH- CH jOH) shows that the chemical shifts for the hydrogen are clearly resolved. (B) h-NMR spectrum from a 55 amino acid fragment of a protein with a role in RNA splicing shows a greater degree of complexity. A large number of peaks are present and many overlap. [(A) After C. Branden and J. Tooze. Introduction to Protein Structure (Garland. 1991), p. 280 (B) courtesy of Dr. Barbara Amann and Dr. Wesley McDermott]...

Figure 3.2 The NMR spectrum of ethanol C2H5OH (lower diagram) in its liquid phase. The upper curve in the form of steps that appear at same S s as bands in the lower spectrum is the integrated spectrum, offset for clarity. S is the chemical shift in parts per million . The (not labelled) ordinate is the absorbed power of the radio wave that defines the NMR intensity. From Canet (42) with permission.

The 300 MHz NMR spectrum of ethanol. This simple alcohol has three types of hydrogen atoms and thus there are three bands. The relative area of the bands is indicated by the vertical displacement of the integral at the top of the spectrum. The relative band area of 1 2 3 is sufficient data to assign all three bands. 

Which would show the signal for the OH proton at a greater chemical shift, the H NMR spectrum of pure ethanol or the H NMR spectrum of ethanol dissolved in CH2CI2 ... 

Figure 24.16 High-resolution NMR spectrum of ethanol. (Courtesy of Carl Esche, Dept, of Chemistry, University of Maryland.)...

Figure 20.27 shows the low-resolution NMR spectrum of ethanol, CH3CH2OH. 

The area under each resonance (whether split or not) is proportioned to the number of protons responsible for that resonance. The NMR instrument will integrate each resonance and produce a vertical fine over it, the height of which is propor-tioned to its area. We are now in a position to consider the complete NMR spectrum of ethanol, with integration, in Fig. 20.28(b). Notice that the heights of the vertical fines over the OH, CH2 and CH3 resonances are in a ratio of 1 2 3, i.e. in accordance with the number ofprotons on each group. 

The accompanying figure also depicts a moderate resolution spectrum of pure ethanol with a trace of tetramethylsilane [TMS, Si(CH3)4] added to adjust chemical shift to a scale where the 12 equivalent hydrogen nuclei in TMS are set to zero ppm (this is called the 8-scale). The H-NMR spectrum of ethanol exhibits the following features ... 

A) Schematic diagram of a simple nuclear magnetic resonance (NMR) spectrometer. The sample is placed in solution in a long, thin tube and spins in a probe sitting in a magnetic and surrounded by radio-frequency (RF) coils B) proton NMR spectrum of ethanol (QH O) with tetramethylsilane (TMS) added as internal standard. On the 8-scale of chemical shifts,... 

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