Alcohol anisotropy

Situation with H-bonding also demands to take into account the fact that alcohols have ability to form various associates or even clusters at normal conditions. The most efficient method for determination of inhomogeneity in the excited states is fluorescence polarization measurements. These methods also frequently applied for studying of solvent viscosity, they may be provided in two variants steady state and time-resolved. Relations for time-resolved and steady state fluorescence anisotropy may be given as [1, 2, 75] ... 

G. B. Strambini and E. Gabellieri, Phosphorescence anisotropy of liver alcohol... 

Since the first report of the nonequivalence phenomenon, approximately 40 chiral substances have been reported to induce enantiomeric nonequivalence in the NMR spectra of a host of solutes. These CSAs are encountered in subsequent discussions. Two qualities considered to be essential in the design of the first reported experiment (3) are evident in nearly all CSA-solute combinations. In all cases, the CSA and the solute have the common feature of complementary functionality, which permits their interaction. Both are in general hydrogen bond donors or acceptors the CSAs are acids, amines, alcohols, sulfoxides, or cyclic compounds such as cyclodextiins, crown ethers, or peptides, which attractively interact with appropriate enantiomeric solutes, engendering different spatial environments for their nuclei. In nearly every case the CSA contains a group of high diamagnetic anisotropy near its asymmetric center, a feature... 

The chemical shift 5, defined by Equation (22), was measured at 40.0 and 15.6 Mc./sec. and was found to be —3 2 relative to water for both SA and SG. The derivatives of the resonance absorptions were recorded in the measurements. If the total anisotropy of the chemical shift of protons in the solid is somewhat less than the line width, the cross-over point of the derivative will correspond to the average value of S as for liquids, and will be directly comparable with the shifts for protons in the liquid state. Comparison of the shift value with those of H3O+ (aqueous) (1 1), S = -1-11, OH (aqueous) (121), S = -1-10 dilute solutions of alcoholic-type protons... 

MacGillavry, C. H. Anisotropy in the so-called amorphous part of polyvinyl alcohol. Rec. trav. chim. 69, 509—514 (1950). 

B. V. Hamon and R. J. Meakins. Australian J. Chem. 6, 27-32 (1953). Dielectric anisotropy in crystalline long-chain alcohols. 

Other carboxylic acids such as 55 have been used to make corresponding diastereoisomeric esters. The choice of aromatic substituent in 55 is made on the basis of the greater anisotropy of the three fused aromatic rings in 55 with respect to phenyl. It has recently been possible to assign configuration to a pair of enantiomeric alcohols directly from the H NMR spectra of their esters with 55. The discussion goes beyond the scope of this text, but for details the work of Fukushi et al. 1 Takahashi et a/.18 and Seco et al 9 should be consulted. 

Various fluorinated diphenylmethanols 36-39 were also enantioresolved as CSDP esters (entries 23-26). In the case of alcohols 36, 37, and 39, their absolute configurations were determined by X-ray crystallography. To those fluorinated alcohols, the method of MaNP acid 3 could be applied for enantioresolution and also for determination of their absolute configurations by the H NMR anisotropy method, as discussed below. Meto-substituted diphenylmethanols 40 and 41 were enantioresolved by the CSDP acid method yielding enantiopure alcohols, the abso-... 

We have discovered that this novel carboxylic acid, MaNP acid 3, is also effective for enantioresolution and simultaneous determination of the absolute configuration of various secondary alcohols by the H NMR anisotropy method [41-52, 56-58]. The results obtained by the H NMR anisotropy mefhod are, of course, consistent wifh those by the X-ray method. Therefore, the methods of CSDP and MaNP acids are useful as complementary molecular tools, as discussed in fhis chapter. 

The NMR Anisotropy Method for Determining the Absolute Configuration of Secondary Alcohols the Sector Rule and Applications [42, 50]... 

Fig. 9.16 Enantioresolution of racemic alcohol as (S)-MaNP esters, and determination of the absolute configuration of the first-eluted fraction by the NMR anisotropy method [38, 45, 50],...

Fig. 9.17 Determination of the absolute configurations of the alcoholic part of the first-eluted esters by the NMR anisotropy method using (S)-(+)-MaN P acid, 3 and the observed Ad values [44],...

Table 9.3 HPLC > separation of diastereomeric esters formed from alcohols with MaNP acid (S)-(+)-3, determination of their absolute configurations by the H NMR anisotropy method, and absolute configurations of recovered chiral alcohols.

Fig. 9.22 The S absolute configuration of alcohol (+)-40 as determined by the H NMR anisotropy method using MaN P acid (a) DCC, DMAP, CSA/CH2CI2, r.t. [39].

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