DEPT

The most widely used method for determining multiplicities of carbon atoms is DEPT (Distortionless Enhancement by Polarization Transfer). This has generally replaced the classical method of recording off-resonance spectra with reduced CH couplings from which the multiplicity could be read directly. 

The DEPT experiment (Doddrell et a/., 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 al., 1983), modified DEPT (MODEPT) (Sbrensen et al., 1984), universal polarization transfer (UPT) (Bendall et al, 1983), and phase oscillations to maximize editing (POMMIE) (Bendall and Pegg, 1983 Bulsing et al, 1984) have been reported. 

DEPT (0 = 135° and 90°) and broad-band decoupled C-NMR spectra of ethyl acrylate are shown. Assign the signals to various carbons of the molecule. 

In Section 3.8.3.2, we noted that the CH3 protons of (CH3)2NCH=0 gave separate peaks at room temperature, but became chemical shift equivalent at about 123°. Of course, the 13C peaks show similar behavior. 

The other experiment worth mentioning, which, by the way, is also obsolete, is the attached proton test or APT. This experiment is based on the different magnitudes of Tl—13C coupling for methine, methylene, and methyl groups. By adjusting certain delays in the pulse sequence (not given), quaternary and methylene carbons could be phased up, and methine and methyl carbons could be phased down. Since phase is arbitrary, this order could be reversed. This ability of distinguishing 

FIGURE 4.11 DEPT pulse sequence. The 1/2 J is for CH coupling constants typically 145 Hz. 6 is a variable pulse angle.-R,/ is a relaxation delay, 6 is a variable pulse angle, f2 is the acquisition time. 

FIGURE 4.12 (a) Standard 13C decoupled spectrum of ipsenol in CDCl3 at 75.5 MHz. (b) DEPT subspectra DEPT 135° CH and CH3 up, CH2 down, (c) DEPT 90° CH only. 

Beyond the number of protons attached to a 13C atom, it would be nice to know which protons are attached to each 13C atom. In other words, what are the correlations Chapter 6 deals with both — H and ir—i c correlations. 

We mentioned in Section 5.4 that a DEPT spectrum distinguishes between a CH3 group, a CH2 group, and a CH group. 

No attempt will be made here to discuss the complex multipulse sequence for DEPT some of the simpler multipulse sequences will be described in Chapter 6. The novel feature in the DEPT sequence is a variable proton pulse that is set at 45°, 90°, or 135° in three separate experiments. The signal intensity at a particular time for each of the three different pulses depends on the number of protons attached to a particular carbon 

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COMMUNICATION PPOF J P.QCONNELL, DEPT CHEM ENG, UNlV FLORIDA. C... 

In the United Kingdom For a complete lisi of books available from Penguin in the U.K., please write to Dept E.P., Penguin Books Ltd, Harmondsworth, Middlesex, UB70DA... 

R.AJ. Soden, R.J. Dewhurst - Dept, of Instrumentation and Analytical Science, UK. 

IzfP Fraunhofer-Institut for NDT, http //mm.fhg.de/depts/izfp-e.html... 

Karlstrdms, M., Magnusson Seger, M., Crack estimation with linear filtered tomosynthesis , ISSN 1400-3902, Dept of Electrical Engineering Linkoping, Sweden (1998). 

The same general methodology ean also be applied to edit (for example) a deeoupled NMR speetnim into four subspeetra, for the CH, CH2, CH and C moieties separately. A eonnnon variant method ealled DEPT... 

In AFM, the relative approach of sample and tip is nonnally stopped after contact is reached. Flowever, the instrument may also be used as a nanoindenter, measuring the penetration deptli of the tip as it is pressed into the surface of the material under test. Infomiation such as the elastic modulus at a given point on the surface may be obtained in tliis way [114], altliough producing enough points to synthesize an elastic modulus image is very time consuming. 

Chaimelling phenomena were studied before Rutherford backscattering was developed as a routine analytical tool. Chaimelling phenomena are also important in ion implantation, where the incident ions can be steered along the lattice planes and rows. Channelling leads to a deep penetration of the incident ions to deptlis below that found in the nonnal, near Gaussian, depth distributions characterized by non-chaimelled energetic ions. Even today, implanted chaimelled... 

Carter E 2000 webpage http //www.chem. ucia. edu/dept/FacuItv/carter. htm I... 

Figure Cl.4.13. Trap modulation experiment showing much greater deptli of ion intensity modulation (by more tlian one order of magnitude) tlian fluorescence or atom number modulation, demonstrating tliat excited atoms are not tire origin of tire associative ionizing collisions.

The polarization properties of single-molecule fluorescence excitation spectra have been explored and utilized to detennine botli tlie molecular transition dipole moment orientation and tlie deptli of single pentacene molecules in a /7-teriDhenyl crystal, taking into account tlie rotation of tlie polarization of tlie excitation light by tlie birefringent... 

BIOSON Research Institute and Dept of Biophysical Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands... 

James F. Leathrum and John A. Board. The parallel fast multipole algorithm in three dimensions. Technical report. Dept, of Electrical Engineering, Duke University, Durham, 1992. 

H. Grubmiiller. Dynamiksimulation sehr groCer Makromolekiile auf einem Parallelrechner. Master s thesis, Physik-Dept. der Tech. Univ. Miinchen, Munich, 1989. 

Dept, of Electrical and Computer Engineering, Duke University, Durham, NC USA... 

Available from New Metals and CheniicaU Ltd.. IG Northumberland Avenue, London, W.C. 2., or from Electrocliemicals Dept.. E.I. dii Punt de Nemours and Co., Wilmington,... 

Major advances m NMR have been made by using a second rf transmitter to irra diate the sample at some point during the sequence There are several such techniques of which we 11 describe just one called distortionless enhancement of polarization transfer, abbreviated as DEPT... 

FIGURE 13 26 NMR spectra of 1 phenyl 1 pentanone (a) Normal spectrum (b) DEPT spec trum recorded using a pulse sequence in which CH3 and CH carbons appear as positive peaks CH2 carbons as negative peaks and carbons without any attached hydrogens are nulled... 

WebSpectra includes 75 problems All the problems display the and C spectra several with DEPT or COSY enhancements A number include IR spectra Organic Structure Elucidation contains 64 problems all with and C NMR IR and mass spectra The exercises in both WebSpectra and Organic Structure Elucidation are graded according to difficulty Give them a try... 

Because the digitized areas of the H spectrum give the relative number of pro tons responsible for each signal HETCOR serves as an alternative to DEPT for count mg the number of protons bonded to each carbon... 

Section 13 18 One of the special techniques for distinguishing carbons according to the number of their attached hydrogens is called DEPT A series of NMR measurements using different pulse sequences gives normal nulled and inverted peaks that allow assignment of primary secondary tertiary and quaternary carbons... 

DEPT (Section 13 18) Abbreviation for distortionless enhance ment of polarization ttansfer DEPT is an NMR technique that reveals the number of hydrogens directly attached to a carbon responsible for a particular signal... 

D. V. Sweet, Kegisty of Toxic Tffects of Chemical Substances, 1986 ed., U.S. Dept, of Health and Human Services, National Institute for Occupational Safety and Health, Cincinnati, Ohio. 

MIE-I-46058C(6f Insulating Compound, Electrical for CoatingPrinted Circuit-Assemblies), U.S. Dept, of Defense, Washington, D.C., Nov. 8, 1982. 

L. G. Ljungdahl and co-workers, CMA Manufacture (II) Improved Bacterial Strain for Acetate Production, Eiual Report, EHWA/RD-86/117, U.S. Dept,... 

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