Butyl alcohol interpretation

For some molecules no molecular ion is visible in the mass spectrum as in ter. butyl alcohol, (CH3)3 COH in which the heaviest ion occurs at mass 59. corresponding to M+ - CH3 (74 - 15). So in such cases care must be taken in the interpretation of the spectra. 

Assuming that Ti(IV) is distributed statistically in all tetrahedral positions, it can be easily seen that even for crystallite sizes of 0,2 m the great majority of T1(IV) is located inside the pore structure. Assuming that every Ti(IV) is a catalytic centre with equal activity, diffusion limitations for molecules of different sizes should be observed. This is in fact the case. It has been shown [27] that the rate of oxidation of primary alcohols decreases regularly as the chain length increases, while for iso-butyl alcohol a sudden drop in the rate is observed. Also the reactivity order of olefins on TS-1 is different from the order observed with homogeneous electrophilic catalysts, while as already indicated very bulky molecules are unreactive when TS-1 is used as the catalyst. All these facts can only be interpreted as due to diffusion limitations of the larger molecules, which means that the catalytic sites are located inside the pore structure of the solid. 

This interpretation was proved correct by considering the oxidation of a sample of diphenylmethane that had an isotopic purity of 97.0% a,a-dideuterio and 2.7% a-deuterio by mass spectrometry. The oxidation rate observed after the initial 15-second period (see Figure 2), during which the undeuterated and monodeuterated material were destroyed, yielded a second-order rate constant, ki = 0.0148 mole"1 per second. There is thus an appreciable isotope effect ku/kD of about 6 in the ionization of diphenylmethane by potassium ferf-butoxide in DMSO(80%)-tert-butyl alcohol (20% ) at 25°C. This compares with a value of fcH/ D of 9.5 reported for the ionization of triphenylmethane (16). The observation of primary isotope effects of this magnitude requires that the protonation of the diphenylmethide ion by tert-butyl alcohol in DMSO solution does not proceed at the diffusion rate which would, by the principle of microscopic reversibility, require the absence of an isotope effect in the deprotonation step. 

The Hines64 showed that, as acids, ethanol, isopropyl alcohol, and tert-butyl alcohol are weaker than water, whereas methanol is stronger. The influence of the solvent could thus be interpreted in terms of equation 1. In methanol, the equilibrium would be more displaced to the right, and the rate of simple ammonolysis and transesterification would be enhanced, with concomitant decrease in the yields of amido sugars. In water (for the ammonolysis of sugar acetates) and in alcohols other than methanol, the equilibrium would be displaced to the left and this would allow operation of the orthoester mechanism a better chance. The isolation, from the reaction in isopropyl alcohol, of mono-O-benzoylated bis(benzamido)alditols, could also be explained on this basis. 

Since the Ti /H2C>2 reduction is an important system for producing OH radicals and has been used for many studies involving alcohols, it is perhaps interesting to note some of the ESR properties of the Ti+++ ion. The aqueous Ti+++ ion is believed to be coordinated as Ti(H2O)g and has no observable ESR spectrum because of the very short relaxation time. However, if the symmetry is reduced to tetragonal or lower, the orbital momentum should be completely quenched and a narrow ESR line is expected. This phenomenon has been observed in water-alcohol solutions (157). Recently Bolton and coworkers (158) have further observed some proton hyperfine structure from the water ligands of the aqueous Ti+++ complex in a 20% butyl alcohol-water solution. There has been a standing controversy in the interpretation of the spectra detected in the Ti(Il I), Ti(IV)-H2C>2 system (159-162). 

Problem 17.12 Cleavage of optically active methyl Acr-butyl ether by anhydrous HBr yields chiefly methyl bromide and. vcc-butyl alcohol the. ver-butyl alcohol has the same configuration and optical purity as the starting material. How do you interpret these results ... 

The irradiation of the acetate (183) in t-butyl alcohol under nitrogen gave the product (184).187 The ring-contraction in this example can be interpreted in terms of Norrish Type I fission followed by elimination of isobutene and... 

Rate coefficients for thermal decomposition of di-t-butyl hypo-nitrite at 50° compared very well with those extrapolated from data in the literature, obtained by very different techniques, and reaction products contained one mole of base for each mole of PQ + consumed, strongly supporting the proposed electron transfer mechanism. It follows that, in 1 1 t-butyl alcohol-H20, t-butoxy radical must possess oxidizing power in excess of that of PQ2+, for which E0 = —446 mV (NHE), and may, therefore, function as a primary one-electron oxidant in reactions at present interpreted in other ways. 

Ionic solvation in H2O + cosolvent mixtures has been the subject of a number of recent communications. Cosolvents have included acetone, form-amide, NN-dimethylformamide, NN-dimethylacetamide, t-butyl alcohol, " and dioxan. Interpretation of H n.m.r. data (173—303 K) for solutions of Be(N03)2 in aqueous acetone solutions has shown that Be is present mainly in the form of tetra-aquo complexes, coexisting with (probably) polymerized hydroxo(oxo)diaquo complexes. The existence of the tetra-aquo complex has been confirmed by analyses of n.m.r. spectra of aqueous Be(N03)2 solutions. The formation of solvated cationic species in HaO+formamide (Na ) and H2O + DMF (Li" ", Na" ", mixtures has also been investigated in a study of the... 

The kinetics of the protophilic dedeuteriation of thieno[2,3-6]-[2- H]- and -[3- H]-thiophen, thieno[3,2-6]-[2- H]- and -[3- H]-thiophen, and benzo[fc]-[2- H]- and -[3- H]-thiophen have been measured. The activation parameters for the deuterium-exchange reactions of the isomeric thienothiophens with t-butyl alcohol catalysed by potassium t-butoxide were determined. The relative deuterium-exchange rate constants for the 2-position in thiophen, the isomeric thienothiophens, and benzo[/>]thiophen were found to be 1 10 9 4, whereas the corresponding relative values for the 3-positions are 1 94 10 65. These partial rate factors were compared with those obtained upon acidic exchange and interpretation was attempted. ... 

Complex (1) is a catalyst for selective oxidation of benzylic, allylic alcohols to aldehydes, and secondary alcohols to ketones using r-butyl hydroperoxide. Primary aliphatic alcohol oxidation failed. The use of cumyl hydroperoxide as radical probe discounted the involvement of i-BuO /t-BuOO. Hammett studies p = -0.47) and kinetic isotope effects kn/ku = 4.8) have been interpreted as suggesting an Ru—OO—Bu-i intermediate oxidant. 

In 23-dihydroxypyrazine and derivatives Honzl (853), from measurements of infrared spectra in chloroform and ultraviolet spectra in aqueous alcohol, has proposed that 5,6-dichloro-l-cyclohexyl-3-hydroxy-2-oxo-l, 2-dihydropyrazine (pA in water 4.66, 5.66) exists in the form (48). The p.m.r. spectra of some 5- and 6-methyl- and 5- and 6-phenyl-2,3-dihydroxypyrazines have been reported (483). In the 2,5-dihydroxypyrazine series, the infrared spectrum (Nujol) of 2-benzyl-3,6-dihydroxy-5-methylpyrazine has been interpreted as indicating that the major tautomeric form present in the solid state was the dihydroxy form (49), but the ultraviolet spectrum in ethanol was considered consistent with the coexistence of the dihydroxy (49) and oxo-hydroxy form, for example, (50), Although the structure (51) has been proposed for 3-butyl-2,5-dihydroxypyrazine (1092), the evidence in favor of this structure is inconclusive. 

Two regioisomeric y9-(phosphatoxy)alkyl radicals (23) and (24), generated from Barton esters in the presence of ter/-butyl thiol and allyl alcohol, gave a single pair of diastereomeric tetrahydrofurans (26) in excellent yield. This result is most readily interpreted in terms of the highly regioselective quenching of a common radical cation (25) with formation of the more stable benzylic radical (Scheme 25) [49]. 

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