Spectroscopy solvent effects

Duthaler, R.O. and Roberts, J.D., Nitrogen-15 nuclear magnetic resonance spectroscopy solvent effects on the 15N chemical shifts of saturated amines and their hydrochlorides, J. Magn. Reson., 34, 129, 1979. 

Piperidin-4-one N-oxide, 2,2,6,6-tetramethyl-solvent effects, 2, 146 Piperidinones stability, 2, 159-161 synthesis, 2, 81, 95 from S-aminopentanoic acids, 2, 402 Piperidin-2-ones IR spectroscopy, 2, 130 synthesis... 

ESI mass spectrometry ive mass spectrometry ESR spectroscopy set EPR spectroscopy ethyl acetate, chain transfer to 295 ethyl acrylate (EA) polymerizalion, transfer constants, to macromonomers 307 ethyl methacrylate (EMA) polymerization combination v.v disproportionation 255, 262 kinetic parameters 219 tacticity, solvent effects 428 thermodynamics 215 ethyl radicals... 

The use of computer simulations to study internal motions and thermodynamic properties is receiving increased attention. One important use of the method is to provide a more fundamental understanding of the molecular information contained in various kinds of experiments on these complex systems. In the first part of this paper we review recent work in our laboratory concerned with the use of computer simulations for the interpretation of experimental probes of molecular structure and dynamics of proteins and nucleic acids. The interplay between computer simulations and three experimental techniques is emphasized (1) nuclear magnetic resonance relaxation spectroscopy, (2) refinement of macro-molecular x-ray structures, and (3) vibrational spectroscopy. The treatment of solvent effects in biopolymer simulations is a difficult problem. It is not possible to study systematically the effect of solvent conditions, e.g. added salt concentration, on biopolymer properties by means of simulations alone. In the last part of the paper we review a more analytical approach we have developed to study polyelectrolyte properties of solvated biopolymers. The results are compared with computer simulations. 

As demonstrated in the two previous sections, TRIR spectroscopy can be used to provide direct structural information concerning organic reactive intermediates in solution as well as kinetic insight into mechanisms of prodnct formation. TRIR spectroscopy can also be used to examine solvent effects by revealing the inflnence of solvent on IR band positions and intensities. For example, TRIR spectroscopy has been used to examine the solvent dependence of some carbonylcarbene singlet-triplet energy gaps. Here, we will focns on TRIR stndies of specific solvation of carbenes. 

We have reported the first example of a ring-opening metathesis polymerization in C02 [144,145]. In this work, bicyclo[2.2.1]hept-2-ene (norbornene) was polymerized in C02 and C02/methanol mixtures using a Ru(H20)6(tos)2 initiator (see Scheme 6). These reactions were carried out at 65 °C and pressure was varied from 60 to 345 bar they resulted in poly(norbornene) with similar conversions and molecular weights as those obtained in other solvent systems. JH NMR spectroscopy of the poly(norbornene) showed that the product from a polymerization in pure methanol had the same structure as the product from the polymerization in pure C02. More interestingly, it was shown that the cis/trans ratio of the polymer microstructure can be controlled by the addition of a methanol cosolvent to the polymerization medium (see Fig. 12). The poly(norbornene) prepared in pure methanol or in methanol/C02 mixtures had a very high trans-vinylene content, while the polymer prepared in pure C02 had very high ds-vinylene content. These results can be explained by the solvent effects on relative populations of the two different possible metal... 

The several theoretical and/or simulation methods developed for modelling the solvation phenomena can be applied to the treatment of solvent effects on chemical reactivity. A variety of systems - ranging from small molecules to very large ones, such as biomolecules [236-238], biological membranes [239] and polymers [240] -and problems - mechanism of organic reactions [25, 79, 223, 241-247], chemical reactions in supercritical fluids [216, 248-250], ultrafast spectroscopy [251-255], electrochemical processes [256, 257], proton transfer [74, 75, 231], electron transfer [76, 77, 104, 258-261], charge transfer reactions and complexes [262-264], molecular and ionic spectra and excited states [24, 265-268], solvent-induced polarizability [221, 269], reaction dynamics [28, 78, 270-276], isomerization [110, 277-279], tautomeric equilibrium [280-282], conformational changes [283], dissociation reactions [199, 200, 227], stability [284] - have been treated by these techniques. Some of these... 

Karelson, M. M. and Zemer, M. C. Theoretical treatment of solvent effects on electronic spectroscopy, J.Phys. Chem., 96 (1992), 6949-6957... 

Ronayne, J., Williams, D. H. Solvent Effects in Proton Magnetic Resonance Spectroscopy. Annual Review of NMR Spectroscopy, Vol. 2,pp. 83-124, New York 1969. Laszlo, P. Solvent Effects and Nuclear Magnetic Resonance. Progr. N.M.R. Spectroscopy 3, 231-403(1968). 

Meso-dl isomerization of [47] was described by Koch (Koch et ah, 1975 Koch, 1986 Olson and Koch, 1986. The intermediate radical [48] is in equilibrium with the dimer and can be easily recognized by esr spectroscopy. The thermodynamic parameters for bond homolysis, as a function of medium, are reported in Table 18. A strong solvent effect is observed, in contrast to Riichardt s example ([24], [25]) reported above. This is interpreted as a manifestation of the polar character of the intermediate radical. The easy detection of [48] by esr spectroscopy is traced back, at least in part, to its captodative character. However, the strong solvent effect on homolysis of [47] need not necessarily be related to the captodative character of radicals [48]. 

Orendorff, C.J., Ducey, M.W., Jr., Pemberton, J.E., and Sander, L.C., Structure-function relationships in high density octadecylsilane stationary phases by Raman spectroscopy 3. Effects of self-associating solvents, AnoZ. Chem., 3360, 2003. 

There have been relatively little ultraviolet-visible (UV-Vis) spectroscopic data for 1,4-oxazines, but selected data are presented in Table 8. UV spectroscopy is important for photochromic compounds, such as spirooxazines. The UV spectra of 33 spirooxazines in five different solvents are collected in a review <2002RCR893>, and the more recently reported examples of photochromic oxazines 65, 66, 101, and 102 are shown here. It can be seen from Table 8 that both adding methoxy substituents to the oxazine and changing to a more polar solvent give a UV maximum at a higher wavelength. This solvent effect can also be seen in the case of 102, which also has important fluorescence properties, discussed in Section 8.06.12.2. 

---