NMR, solvents

Figure 1.4. Space-filling models of cyclosporin A. (a) Solid-state conformation (X-ray analysis) (b) computer-generated conformation in apolar solvents (NMR measurements).

U.K.), with a normal sweep width of 1000 Hz and sweep time of 500 s. Fourier transform PMR spectra were recorded using a Bruker WH 300 instrument (Bruker Instruments Inc., Manning Park, Billerica, MA 01821, USA) and methanol-d as solvent (NMR Ltd). 

Fig. 7.18. Solvent NMR chemical shifts recorded in lanthanide perchlorate solutions, (a) DMF formyl 1H in pure DMF (open circles are for ambient pressure measurements filled circles are for measurements done at 200 MPa), (b) Water, 70 in 2.0 M H 1 aqueous solutions [33].

Solvent NMR studies of some Co(ii), Ni(ii), and Cu(ii) complexes with the Schiff base [49] have been performed. (276, 277) The complex is involved in the equilibrium ... 

All the compounds lose olefin when exposed to air. They should be stored in tightly closed containers and kept in a refrigerator. The compounds are soluble in halogenated solvents. Nmr data are given in Table I. Infrared spectra have two intense characteristic absorptions in the region 1610-1680 cm i (one may be a shoulder). 

It has recently been found that salts which melt at or near room temperature, so-called ionic liquids, can form physical solutions of cellulose and starch. l-A -Butyl-3-methylimidazolium chloride dissolved plant and bacterial cellulose with no apparent loss of DP, and cellulose in the resulting solutions was much more readily derivatised to various esters than in the solid (Figure 4.34d). The same applied to l-A -allyl-3-methylimidazolium chloride in both solvents, NMR indicated that the cellulose chains were disordered in solution.Studies... 

Ultraviolet spectra (solvent) NMR spectra (solvent) Infrared spectra (vehicle) ... 

General procedure for the one-pot Fischer Indole synthesis To allow comparison of the data, a procedure similar to that described in ref. [5] was used. The catalyst (3.00 g) was suspended into a solution of 1 -phenyl-2-butanone (1.48 g, 10.0 mmoles) in p-xylene (30 g). The mixture was then heated to reflux, and after 15 minutes phenylhydrazine (1.08 g, 10 mmoles) was added in one portion. Samples were taken at regular intervals and analyzed by GC using a CP Sil-5 CB capillary column. In several cases, the indole isomer mixture was isolated from the reaction mixture by vacuum distillation after removal of the catalyst and the solvent. NMR shift values and coupling constants for 4 and 5 were identical to those reported in ref. 

The type and distribution of sulfidic links - mono, di, or poly - affects the properties of the vulcanized rubber and these are determined by scission with specific chemical reagents followed by determining the degree of swelling in a suitable solvent. NMR methods have also been developed to determine cross-linking. 

Cysteamine (HSCH2CH2NH2) has been found to add to Michael acceptors, such as thujone, in dimethylsulfoxide (DMSO). By contrast, no reaction occurred in nonpolar solvents. NMR spectroscopy was employed to identify good Michael acceptors and sort them into reversible and irreversible thiol sinks with a view of developing a cellular assay for thiol-trapping agents. In another paper, calculated transition-state energies of the reaction of Michael acceptors with MeSH have been used as model system to asses thiol toxicity in aqueous media. ... 

Later, Grubbs and coworkers synthesized 121 by an alternative synthetic route and confirmed its decomposition in chlorinated solvent. NMR studies suggested that the rapid decomposition of this complex was due to dissociation of NHC from the metal center [105]. 

As base hydrolysis was deemed unsuitable, acid hydrolysis was investigated. The ethyl ester ligand was dissolved in 1 M HCI and stirred at 80 °C for 4 days (Eig. 8.2). After removal of the solvent, NMR analysis showed that the desired carboxylic acid compound was obtained as hydrochloride in acceptable yield (50 %) with all nitrogen atoms protonated. 

In such cases, plots of NMR shifts against infrared band maxima are linear for many pure solvents. A good example is that for EtjPO where the shift is correlated with v(P-0) (Figure 3.14). The only data that fail to fit the linear correlation are those for methanol and ethanol. However, for these solvents two distinct infrared bands are resolved. If the weighted mean of these bands is used, the correlation with the NMR data is good. In order to interpret mixed solvent NMR shifts, we make the assumption that this plot can be used to estimate NMR shifts for specific solvates from v (P-O). It is on this basis that NMR solvent shifts can be reconstructed. The comparison with experi-... 

Additional tools can help to break down perceived barriers to the usage of some of the more unfamiliar solvents. Building on the frequent use made of lists of peaks arising from trace residual solvents in common deuterated NMR solvents, NMR guides emphasising the peaks of some of the less familiar and potentially greener solvents in common deuterated NMR solvents (chloroform, DMSO, methanol, water, acetone and acetonitrile), can help act as a reminder of different options and help remove some of the barriers to their uptake. 

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