Methanol complexes

Limestone Methanol Complexation Adsorption Bacterial sulfate and iron reduction Methane production... 

The methanol complex [Rh(BINAP) (MeOH)2]ClC>4 and the complex resulting from loss of MeOH from it are used as catalysts [47]. Both BINAP enantiomers were employed. 

These /6-aromatic complexes are not easily spotted by routine NMR measurements, as 31P-NMR data for aromatic and methanol complexes are very similar (Table 44.2). However, the two types of complexes can be distinguished unequivocally by using 103Rh-NMR spectroscopy [48,49]. 

Figure 9.2 Transfer hydrogenation of ketones catalyzed by Ru(II)(2-azanorbornyl-methanol) complexes.

LAS Soil Alkaline methanol Complexation/extraction Photometer [29]... 

We made a similar observation when we reported a mild and efficient radical mediated reduction of organoboranes (Scheme 58, Eq. 58a) [128]. An in situ generated B-methoxycatecholborane-methanol complex acts as a reducing agent. The radical nature of the process was demonstrated by using (+)-2-carene as a radical probe (Eq. 58b). Water, ethanol and trifluoroethanol can be used instead of MeOH with very similar efficiency. 

Pyrimidinylidenemalonate (1653) was converted into the isopropyli-dene derivative (1654) in 70% yield by treatment with the boron trifluoride methanol complex in methylene chloride and then with 2,2-dimethoxypro-pane (87TL2821). 

In another study (40) we found that protonation of pyridine is diffusion-controlled with a one-to-one solute-methanol complex as the reactive species. Thus, while methanol plays essentially no role in the proton transfer to dipicrylamine in the first study, it is indeed intimately involved in the proton transfer to pyridine. 

The MM2 model resides very near the minimum 2 in the cellobiose energy map (cf. Fig. 9). (Among others, the crystal structure of methyl cellobioside-methanol complex is found in that minimum (15)). On the other hand, the PS79 model resides on the shallow saddle point between minima 2 and 3. 

Solvato complexes of platinum(II) of the type fraws-[PtY(solvent)L2]+ (Y = hydride, alkyl, or aryl solvent = alcohol or ketone L = tertiary phosphine or arsine) have been known since 1961.1 They are obtained by halogen abstraction from the corresponding halo complexes tran.s-[PtXYL2] in the presence of the desired solvent.2 The methanol complex is also rapidly and quantitatively formed when trans-[PtH(N03)(PEt3)2] is dissolved in this solvent.2... 

Hydrogenating enamide (see Complex 10) in methanol solution causes an extremely rapid reversion to the methanol complex with no observable intermediates. If the sample is cooled to -80°C before hydrogen is introduced and then agitated at -50°C for several minutes the P-31 NMR spectrum shows Complex 10a and about 10% of a new species with similar chemical shifts but very different P-P and P-Rh... 

Place 9.4 g (0.06 mol) of m-chlorobenzoic acid and 66 ml (0.12 mol) of boron trifluoride-methanol complex (14% w/v of BF3 Section 4.2.8, p. 421) in a 250-ml round-bottomed flask. Heat the mixture under reflux on an oil bath for 2 hours, cool and pour into about 250 ml of saturated sodium hydrogen carbonate solution. Extract the organic product with three 50 ml portions of ether, dry the ethereal extract over magnesium sulphate and evaporate on a rotary evaporator. Distil the residue under reduced pressure and collect the methyl m-chlorobenzoate as a colourless liquid of b.p. 63 °C/3mmHg the yield is 9.3 g (91%). 

This paper presents quantum mechanical studies of the, 5N and, 3C chemical shifts in both the N7-H and N9-H tautomeric forms of purine. Quantum mechanical calculations of the chemical shifts were used to assign the NMR resonances and the spatial orientation of the principal axes of the chemical shift tensors. Calculations in purine and in a pyridine-methanol complex model provide insights on the importance of the intermolecular interactions on the chemical shifts of the nucleic acid bases. 

It is apparent from the calculations in the model pyridine-methanol system, that various principal components of the chemical shift tensor are affected differently by the HB. Consequentely, the principal values perpendicular to the direction of the interaction will exhibit a greater effect than the shielding components along the direction of the interaction. This general argument is in agreement with the qualitative observations in purine. A full 3D study of the interaction in the pyridine-methanol complex is required to quantitatively interpret the results in purine. 

Figure 4 Dependence of the 15N principal values of the chemical shift in pyridine with the N-H distance for the pyridine-methanol complex. Note the different chemical shift scales for each shift component, SUj <%2, 3 and < so. The N-H distances are in A and the horizontal scales in the figure are the same for all the shift components.

The 15N chemical shift tensors in purine are similar to those in other nucleic acid bases for similar types of nitrogens. Comparison of the calculated values in purine for the isolated molecule and for the molecule with its nearest neighbors shows well defined trends, which could be rationalized using the results in the model pyridine-methanol complex. 

Studies have also been carried out in systems containing excess BF3 (17,18). The results (18) show that when the base is dimethyl ether, anisole, tetrahydrofuran, or pyridine, the exchange of BF3 is rapid and probably proceeds through an electrophilic displacement reaction in which the excess BF3 attacks the complex. These reactions all have activation energies of less than 10 kcal/mole, eliminating the possibility of a dissociation process. The data available, however, do not allow a complete evaluation of the reaction mechanism. Studies carried out on BF3-methanol complexes by 19F NMR (17) indicate displacement reactions having an activation energy of 5.3 kcal/mole. 

Table 4. Comparison of AH and Av for gas-phase amine-methanol complex formation. From D. J. Millen and G. W. Mines. J.C.S. Faraday Trans. II. 70,693 (1974). Reproduced by permission from the Chemical Society.

The mixed-valent [Fe(II)Fe(III)] state of MMOH from has the ability to accommodate simultaneously several molecules (methanol, water and DMSO) as recently demonsrated by ENDOR spectroscopy (Willems et al., 1998). The structure of the binuclear iron-methanol complex and the detailed mechanism of the complex dissociation were investigated with the use of density function methods (Bash et al., 2001a.b). 

Basch, H., Musaev, D.G., Mogi, K. and Morokuma, K. (2001b) A density ftinctunal study of the completion of the methane monooxygenase catalytic cycle. Methanol complex to MMOH resing state, J. Phys. Chem. B 105, 8452-8460. 

Complex formation with substrate (S) can proceed directly, by route A, to yield a relaxed a-cyclodextrin with all six 0(2) -0(3 ) hydrogen bonds engaged (as in the a-cyclodextrin methanol complex, Fig. 18.8), or the macrocycle can first open up to a relaxed form, route B, with the enclosed water molecules disordered over several sites so as to fill, statistically, the 5 A diameter a-cydodextrin cavity (as observed in the a-cyclodextrin 7.57H20 crystal struc- ture, Fig. 18.6 b). The water is now in an activated form and can be replaced directly by the j substrate. In a third possible mechanism, route C, the substrate aggregates first at the periphery of tense a-cyclodextrin, and in a second step replaces the two enclosed water molecules. 

Conditions for the formation of potato starch-alcohol complexes do not follow predictable trends. For example, all complexes are formed more readily from air-dried starch rather than from oven-dried starch. Only the starch-methanol complex favors room temperature for its formation the other alcohols require elevated temperatures for effective complexations (see Table XXXI).659,681 682 In contrast, moisture inhibits the formation of the starch-(-)-menthol complex, which is characterized as an interchain complex.710 The Scatchard binding parameters show that (-)-menthol and 1-hexanol adsorb on starch by only one mode, whereas 1-octanol and 1-decanol adsorb in two modes.656 The results for the latter two alcohols indicate that the helices are not fully filled before the second mode of complexation starts. Temperatures of the formation of starch-alcohol complexes likewise do not follow any clear relationship.673,680 Bushuk and Winkler687 reported that the amount of guest molecules (HzO, MeOH,... 

Diethyl ether 3.3—3.8 20 Room temp. Starch-methanol complex... 

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