T-Butyl alcohol, as solvent

There have been efforts to enhance stereoselectivity in radical polymerization by using fluoroalcohols or Lewis acids that complex with monomers such as MMA and vinyl acetate [Isobe et al., 2000, 2001a Okamoto et al., 2002], In almost all instances the effects are nil or very small. For example, the use of perfluoro-t-butyl alcohol as solvent instead of toluene changes (rr) from 0.89 to 0.91 in the polymerization of MMA at —78°C. An exception is in the polymerization of acrylamide in the presence of some rare-earth Lewis acids such as ytterbium triflate. The polymer is atactic at 0°C, (m) = 0.46, in the absence of the Lewis acid, but significantly isotactic, (m) — 0.80, in the presence of the Lewis acid. The reason for this effect is unclear. More highly isoselective polymerization occurs in some radical polymerizations of MMA (Sec. 8-14b). 

The major limitation of the potential value of the Venturello-Ishii systems, however, is related to the use of toxic and industrially undesirable chlorinated solvents , defeating the environmental advantages of H2O2 as primary oxygen source . In this respect, the PCWP catalytic system was modified by using t-butyl alcohol as solvent and by... 

Alkylation of the dienolate ion derived from 4-methyl-19-nortestosterone (313) with CD3I in benzene solution gave the 4,4-dimethyl compound (314), with 70% of the labelled methyl groups in the 4j5-orientation. With t-butyl alcohol as solvent the product showed predominant (90%) introduction of 4a-CD3 (iWs latter conclusion, which reverses that reached in an earlier study, depended upon application of the nuclear Overhauser effect for the assignment of n.m.r. signals of the C-4 methyl groups). Solvent-dependence of the stereochemistry of alkylation has not been suspected before. ... 

As in organic chemistry where m values for bromides are rather lower than for chlorides, for example m — 0.92 for t-butyl bromide compared with m = 1.00 for t-butyl chloride, m values for cobalt(ra)-amine-bromide complexes are, at around 0.2, rather lower than for the analogous chlorides. Whereas in this work the effect of solvent structure on reaction rates has been used to gain further insight into reaction mechanisms, the opposite approach has also been used, in a study of aquation of tra/u-[Co(en)2Cl2]+ in alcohol-water mixtures, in which variation of rate with solvent composition has been used as a probe of solvent structure variation. Rates of aquation of both cis- and trans-[Co ea)2C have been determined in aqueous acetonitrile (0 < mole fraction MeCN < 0,104). For both complexes aquation rates decrease only slightly as the proportion of acetonitrile increases, with the cir-complex slightly more sensitive to solvent variation. The kinetic effects observed here are smaller than those observed in t-butyl alcohol-water solvent mixtures. ... 

A major disadvantage of Kraus s procedure in terms of an environmentally benign method involved the use of benzene (or alternatively acetonitrile) as solvent. Supercritical carbon dioxide (SC-COj) was recently reported as an alternative solvent and was applied to the benzophenone-mediated photoacylation of 1,4-benzoquinone (5) with benzaldehyde or butyraldehyde, respectively. " High yields of up to 81% were achieved at higher CO pressure, or with the addition of 5% t-butyl alcohol as co-solvent (Table 88.12) the latter is necessary due to the limited solubility of the quinone in SC-COj. Despite these achievements, this technique suffers from technical disadvantages (e.g., high pressure or small reactor volume), especially for a large-scale application. 

In several separate small scale experiments, It was noted that the coupling reaction was not impeded by adding pyridine, triethylamine, t-butyl alcohol, chlorotrimethylsilane, or diisopropylamine to the reaction mixture before adding the nickel catalyst. These results suggest that a variety of functional groups can be present in the enone partner of the coupling reaction. In addition toluene can be used instead of tetrahydrofuran as the solvent. 

The reaction appears to be more rapid when carried out in the presence of a strong base, such as potassium /-butoxide in a dimethyl sulfoxide-t-butyl alcohol (80 20) solvent system. The preparation of o,o,p-trideuterioazobenzene is an example of this preparation [35],... 

The lifetimes of the BRs are of critical importance to any attempt at quantitative analysis of the factors which will determine quantum yields and product distributions (E/C and t/c ratios) in Type II reactions of ketones under various reaction conditions. Virtually all information about lifetimes is derived from study of triplet BRs and much of it has been provided, and reviewed, by Scaiano [261]. There are many interesting reactions, both bimolecular and unimolecular, which occur at only one of the radical centers but they have little relevance to this chapter and are not discussed here. BR triplets derived from alkanophenones have lifetimes of 25-50 ns in hydrocarbon solvents. They are lengthened several fold in t-butyl alcohol and other Lewis bases capable of hydrogen bonding to the OH groups of the BRs. The rates of decay are virtually temperature independent but are shortened by paramagnetic cosolutes such as 02 or NO. The quenchers react with the BRs... 

Figure 46. Solvent dependence of the partial molar heat capacity of sodium tetraphenyl-borate in t-butyl alcohol + water mixtures at 298 K as a function of alcohol mole fraction, xj (Arnett and McKelvey, 1966b).

The dependence of volumes of activation, AV, on solvent composition for the hydrolysis of benzyl chloride in aqueous mixtures (Golinkin et al., 1966 Hyne et al., 1966) has been analysed using the solvent dependence of the partial molar volume of the initial state (Golinkin et al., 1967). In aqueous alcohols, as x2 increases, AV decreases to a minimum value at a mole fraction characteristic of the alcohol, e.g. x2 =0-1 for t-butyl alcohol, the intensity of the extremum increasing on going from methyl alcohol to t-butyl alcohol. The dependence of AV on x2 is a consequence of quite marked changes in the quantities 5m Vf and 8m V (Dickson and Hyne, 1971). For example, in ethyl alcohol + water mixtures, 5m V for benzyl chloride in the initial state has a maximum near x2 = 0-3, whereas 5m V has a shallow minimum near x2 = 0-1 (cf. V2 for Me4N+Cl- in these mixtures Lee and Hyne,... 

In view of the already extensive and rapidly expanding literature concerning NMA, the present comprehensive review will be restricted to the use of pure NMA as a solvent. The literature has been covered rigorously through 1975 and in major part through 1976. Much of the NMA-related literature, especially that in the 1970 s, deals with the properties and chemistry of mixed-solvent systems in which NMA is combined with water, N,N-dimethylformamide, N,N-dimethylacetamide, t-butyl alcohol, dimethyl sulfoxide, or other solvents hence, it is currently anticipated that the broad topic of NMA-containing mixed-solvent systems will be covered in another review. 

To provide an internal reference, the solvent is sealed in a capillary, which is placed at the bottom of the NMR tube used for the sample solution. For this purpose, a melting-point capillary is closed at one end and a syringe is used to add the reference solution. For aqueous studies, a 2% solution of t-butyl alcohol in water can be used as reference and as solvent for the paramagnetic solute. The shift with respect to the methyl resonance of the r-butyl group is then monitored. With organic ligands such as acetylacetonate (acac) groups, complexes such as Cr(acac)3, Fe(acac)3, and Co(acac)2 are soluble in benzene and the proton resonance of the solvent is a convenient reference. The capillary is filled one-third full, the lower end of the capillary is cooled in ice, and the upper part is sealed off with a small hot flame. Alternatively, the reference solution can be placed in one compartment of a coaxial pair of cyhndrical NMR tubes, which are available commercially. In either case the spectral display should be expanded to permit an accurate measurement of the frequency shift. 

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