DEPT spectra

The hydrolysis of 3-ethoxy-4-ethylbicyclo[4.1.0]hept-4-en-7-one propylene acetal (1) with aqueous acetic acid in tetrahydrofiiran gives an oil with the molecular formula CnH/gOi, from which the INADEQUATE contour plot 22 and DEPT spectra were obtained. What is the compound ... 

The correlation signals of the INADEQUATE experiment directly build up the ring skeleton A of the compound. Elere characteristic C shifts (5c = 123.1, 137.6 148.9, 109.1) establish the existence and position of two double bonds and of one tetrahedral C-0 single bond (5c = 70.5). DEPT spectra for the analysis of the CH multiplicities become unnecessary, because the INADEQUATE plot itself gives the number of CC bonds that radiate from each C atom. 

Table 50.1. Interpretation of the CH COSY plot and the DEPT spectra...

Figure 3. NMR-DEPT spectra of maitotoxin in CD3CN-D2O (1 1) A, methyls and methines appear as positive peaks and methylenes as negative peaks B, only methines appear C, no quarternary carbons appear and D, a conventional noise-decoupled spectrum.

The DEPT experiment (Doddrell elal, 1982) involves a similar polarization transfer as the INEPT experiment, except it has the advantage that all the C signals are in phase at the start of acquisition so there is no need for an extra refocusing delay as in the refocused INEPT experiment. Coupled DEPT spectra, if recorded, would therefore retain the familiar phasing and multiplet structures (1 1 for doublets, 1 2 1 for triplets, etc.). Moreover, DEPT experiments do not require as accurate a setting of delays between pulses as do INEPT experiments. 

Many modifications of DEPT, spectra such as DEPT, DEPT (Sorensen and Ernst, 1983), DEPT GL (Sorensen et ai, 1983), modified DEPT (MODEPT) (Sdrensen et al., 1984), universal polarization transfer (UPT) (Bendall et ai, 1983), and phase oscillations to maximize editing (POMMIE) (Bendall and Pegg, 1983 Bulsing et al, 1984) have been reported. 

The broad-band decoupled C-NMR spectrum of ethyl acrylate shows five carbon resonances the DEPT (6 = 135°) spectrum displays only four signals i.e., only the protonated carbons appear, since the quaternary carbonyl carbon signal does not appear in the DEPT spectrum. The CH and CH3 carbons appear with positive amplitudes, and the CHj carbons appear with negative amplitudes. The DEPT (6 = 90°) spectrum displays only the methine carbons. It is therefore possible to distinguish between CH3 carbons from CH carbons. Since the broadband decoupled C spectrum contains all carbons (including quaternary carbons), whereas the DEPT spectra do not show the quaternary carbons, it is possible to differentiate between quaternary carbons from CH, CHj, and CH3 carbons by examining the additional peaks in the broad-band spectrum versus DEPT spectra. The chemical shifts assigned to the various carbons are presented around the structure. 

In the DEPT experiment, all the signals of the insensitive nuclei are in phase at the start of acquisition, so no refocusing period A (with accompanying loss in sensitivity) is required. Since the multiplets appear in-phase, it is called a distortionless experiment. Moreover, DEPT spectra depend on the angle 0 of the last polarization transfer pulse, and are less dependent on the delay times between the pulses. An error of 20% in the estimation of/values still affords acceptable DEPT... 

Fig. 5.5.15 Spatially resolved 13C DEPT spectra recorded for the competitive etherification and hydration reactions of 2-methyl-2-butene (2M2B) to 2-methoxy-2-methylbutane (tert-amyl methyl ether, TAME) and 2-methyl-butan-2-ol (tert-amyl alcohol, TAOH), respectively. The molar composition of the feed was in the ratio 2 10 1 for 2M2B methanol water. The...

You may be told that your NMR laboratory does not routinely use APT spectra but provides DEPT spectra (Distortionless Enhancement by Polarization Transfer) instead. This is no problem, as DEPT spectra also provide you with the information you need just go back and read what we have said about the relative merits of APT and DEPT. 

IR no bands characteristic of functional groups 200 MHz, solvent CDC13 H, l3C and DEPT spectra... 

MHz, solvent CDC13 APT and DEPT spectra expansion peak frequency in Hz... 

The 13C NMR spectrum of valproic acid was obtained using a Bruker Avance Instrument operating at 75, 100, and 125 MHz. Standard Bruker Software was used to obtain DEPT spectra. The sample was dissolved in D20 and tetra-methylsilane (TMS) was used as the internal standard. The 13C NMR spectrum of valproic acid is shown in Fig. 10. The DEPT NMR spectra are shown in Figs. 11 and 12. The assignments for the various carbons of valproic acid are presented in Table 4. 

C-21 methyl protons. The C-3 and C-16 melhine protons appeared at 8 3.82 and 4.99, respectively. The downfield chemical shift values of C-3 and C-6 methine protons were indicative of the presence of geminal oxygen functionahties. The C-6 resonated at 8 5.36 while the sp hybridized C-28 methylene protons resonated as two singlets, integrating for one proton each, at 8 5.56 and 6.06. A combination of H and C-NMR spectral data indicated to us that compound 11 has a steroidal skeleton. A detailed interpretation of broad C-NMR and DEPT spectra revealed the presence of three metlyl, ten methylene, eight methine and five quaternary carbon atoms in 11. The stereochemistry at various chiral centers was estabhshed with the aid of NOESY spectrum. 

The C NMR spectmm of 13 showed the resonances of all 35 carbon atoms. A combirration of broadband C-NMR and DEPT spectra indicated the presence of 7 methyl, 4 methylene, 16 methine and 8 quaterrrary carbon atoms in compound 13. Complete 13C-NMR chemical shift assignments of 13 are shown around structure 13. Based on these spectral data, structure 13 was established for this new compound. 

This programme turns DQF-COSY and HMBC spectra into bond constraints. Then it turns C DEPT spectra and the molecular formula into building blocks such as -CH3 and -CH2-. These are then assembled into as many complete structures as are compatible with the bond constraints. CISOC-SES is designed to be as compatible with real-world spectra with their attendant ambiguities as possible. CISOC-SES is a result of collaborative work with Bodenhausen et al. who had previously tackled the problem indepen-dently. CISOC-SES has since been commercialized as NMR-SAMS by Spectrum Research, EEC. 

The C-NMR spectra of procaine hydrochloride in DMSO-d were recorded on a Varian XL 200 (200 MHz spectrometer), using tetramethyl-silane as the internal standard. The APT and DEPT spectra are presented in Figures 8 and 9, respectively. Assignments for the observed resonance bands are provided in Table 4, together with the carbon numbering scheme. 

Figure 13.6 is the proton-decoupled carbon-13 NMR distortionless enhancement of polarization transfer (DEPT) spectra of poly(methyl-l-pentene) [29]. This experiment, after data manipulation, separates the methine, methylene, and... 

DEPT Spectra Identifying Quaternary, Methine, Methylene and Methyl Carbons... 

As DEPT relies on the transfer of polarization from a directly bonded H atom to the carbon - resulting in the increased sensitivity of the carbon atoms - only C atoms that are attached to H atoms are detectable by this method, and so no quaternary carbon atoms are seen on DEPT spectra. Depending upon something called the pulse angle (which is expressed as a number after the acronym, but we do not need to know its significance), there are three different DEPT experiments that can be carried out on a particular sample. 

Although quaternary carbons do not appear on DEPT spectra, we can identify them by comparing DEPT and proton decoupled spectra. 

Load the other C DEPT spectra of glucose using the previously stored... 

The multiplication of the FID s(t) with a factor a is equivalent to a multiplication of the spectrum S(f) with the same factor. This equivalence may be exploited e.g. in spectral editing to obtain multiplicity selective C subspectra from the DEPT-45, DEPT-90 and the DEPT-135 data. The multiplication with the corresponding factors may be performed with the DEPT FIDs or the DEPT spectra. 

CH, CH,). Compare the DEPT spectra with the basic ID C spectrum to assign... 

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