Solids, NMR spectroscopy

Some very important surface properties of solids can be properly characterized only by certain wet chemical techniques, some of which are currently under rapid improvement. Studies of adsorption from solution allow determination of the surface density of adsorbing sites, and the characterization of the surface forces involved (the energy of dispersion forces, the strength of acidic or basic sites and the surface density of coul-ombic charge). Adsorption studies can now be extended with some newer spectroscopic tools (Fourier-transform infra-red spectroscopy, laser Raman spectroscopy, and solid NMR spectroscopy), as well as convenient modern versions of older techniques (Doppler electrophoresis, flow microcalorimetry, and automated ellipsometry). 

A multitude of characterisation techniques were used to evidence the occurrence of the different reaction sequences Fourier transform infrared spectroscopy (FTIRS), solid NMR spectroscopy (C-PMAS) (Figure 17.17), contact angle measurements, and X-ray photoelectron spectroscopy (XPS) (Figure 17.18). 

M. Murakami, Fundamentals and Applications of P Solid NMR Spectroscopy , Phosphorus Letter, 2008, 63, 20. 

NMR spectra of solids are often simpler than those of liquids (because the lower inherent resolution of the solid spectra limits the number of resolvable lines), and the information which can be obtained from the analysis of these spectra is considerably less. Solid NMR spectroscopy of crosslinked polymeric systems has been reviewed elsewhere [135]. 

These limitations have recently been eliminated using solid-state sources of femtosecond pulses. Most of the femtosecond dye laser teclmology that was in wide use in the late 1980s [11] has been rendered obsolete by tliree teclmical developments the self-mode-locked Ti-sapphire oscillator [23, 24, 25, 26 and 27], the chirped-pulse, solid-state amplifier (CPA) [28, 29, 30 and 31], and the non-collinearly pumped optical parametric amplifier (OPA) [32, 33 and 34]- Moreover, although a number of investigators still construct home-built systems with narrowly chosen capabilities, it is now possible to obtain versatile, nearly state-of-the-art apparatus of the type described below Ifom commercial sources. Just as home-built NMR spectrometers capable of multidimensional or solid-state spectroscopies were still being home built in the late 1970s and now are almost exclusively based on commercially prepared apparatus, it is reasonable to expect that ultrafast spectroscopy in the next decade will be conducted almost exclusively with apparatus ifom conmiercial sources based around entirely solid-state systems. 

Organic thionylamines have planar, cis structures (9.9) in the solid state and in solution, as determined by X-ray crystallography and N NMR spectroscopy, respectively. The gas-phase structures of the parent compound HNSO and MeNSO have been determined by microwave spectroscopy. The S=N and S=0 double bond lengths are 1.51-1.52 and 1.45-1.47 A, respectively. The bond angle [Pg.168]

The tautomeric relationships for benzisothiazolamidines 100 are more complicated (Scheme 38) (95AP217). In the solid, compound 100 (R = Ph, R = H) exists in the amino form 100a, whereas in a DMSO-d solution at 298 K the tautomers 100b,c have also been detected using NMR spectroscopy. 

Tlie IR and and NMR spectra for thiazolo[5,4-h]quinolines 86 demonstrate their existence in the hydroxy form (96T11929). Tlie preference for IH,6H tautomer 87a in water and in the solid state is supported by and NMR spectroscopy, ab initio (STO-3G ) and X-ray crystallographic studies [75AX(B)1427 92H1399]. 

Pyrido[3,4-fe]pyraziii-3- and -2-oiies exist in the enamino forms 171 and 172 respectively in DMSO-dg ( H NMR spectroscopy) and in the solid state (IR spectra in nujol), and temperature appears not to affect these imine-enamine equilibria (97JHC773). 

H NMR spectroscopy frequently has been used in kinetic studies, for example, in the isomerization of 2,4,6-triphenyl-4//-thiopyran 56 (R= Ph) to its 2//-isomer 60 (R = H, 81JHC1517). l25Te NMR spectra were also measured for 4//-teluropyran 77 and related compounds (88MI1). Oxo-enol tautomerism of 4-hydroxy-2//-thiopyrans llOa-c in the solid state as well as in CDC13 solution was successfully studied by l3C NMR [86JCS(P2) 1887]. 

A solution of 1.0 g (33 mmol) of the mixture of heptofuranoside diastereomers (14) in 5 ntL of THE is stirred in an ice-water bath. 3.4 mL of 1 M soln ofTBAF (3.4 mmol) in THF are added, and Ihe reaction is monitored by TLC (CHCI,/CH, OH, 9 1). After ca. 15 min, the reaction mixture is carefully neutralized with dil sulfuric acid, then diluted with water and extracted with CHC13. The extract is dried over Na,S04 and concentrated to give an off-white solid which is a single stereoisomer (by NMR spectroscopy). Column chromatography gives the inositol as a white solid yield 0.61 g (70%) mp 186-187 C (benzene/CH,OH) [a]D + 118 (c = 03, CH, OH). 

A Relaxation time measurement in the solid (Al) in solution (A2). B Mechanical spectroscopy. C Variable-temperature NMR spectroscopy (coalescence temperature measurement). D Variable-temperature EPR spectroscopy... 

The incorporation of water in the structure of cellulose influences. Upon the hydrogen bond structure of the macromolecule. A great deal of work has been done in this area. Calorimetric methods have been invaluable in helping to solve the problem 23 It is, however evident that solid-state NMR spectroscopy may also give valuable information. 

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