2, 2, 2-Trifluoroethanol

McFadden C F and Geiiman A J 1995 Ultra-high vacuum boundary lubrication of the Cu-Cu interface by 2,2,2-trifluoroethanol Langmuir 273-80... 

Cyclopentadiene (2.5) was prepared from its dimer (Merck-Schuchardt) immediately before use. Dimineralised water was distilled twice in a quartz distillation unit. Ethanol (Merck) was of the highest purity available. Acetonitrile (Janssen) was mn over basic aluminium oxide prior to use. 2,2,2-Trifluoroethanol (Acros) was purified by distillation (bp 79 - C). Co(N03)2 6H20,... 

Difluoroethanol [359-13-7], F2CHCH2OH, is a colorless Hquid with an alcohol-like odor mp, 28.2°C, bp, 96°C d[, 1.3084 n], 1.3320 heat of combustion, —1026 kJ/mol(—245.3 kcal/mol). It is stable to distillation and miscible with water and many organic solvents. As expected, its acidity Hes between that of 2-fluoroethanol and 2,2,2-trifluoroethanol both ia the gas phase (25) and ia 50% aqueous ethanol solution (26), where its of 1.0 x 10 is about 4.8 times smaller than that of trifluoroethanol. 

Chemically, 2,2,2-trifluoroethanol behaves as a typical alcohol. It can be converted to trifluoroacetaldehyde [75-90-1] or trifluoroacetic acid [76-05-1] by various oxidi2iag agents such as aqueous chlorine solutions (51) or oxygen ia the preseace of a vanadium pentoxide catalyst (52). Under basic conditions, it adds to tetrafluoroethylene and acetylene to give, respectively, 1,1,2,2-tetrafluoroethyl 2/2/2 -trifluoroethyl ether [406-78-0] (53) and... 

Trifluoroethanol is also the starting material for the anesthetic Isoflurane (l-chloro-2,2,2-trifluoroethyl difluoromethyl ether [26675-46-7]) (55,56) and Desflurane (2-difluoromethoxy-l,l,l,2-tetrafluoroethane [57041-67-5]) (57). 

The configurations of chiral thiiranes and thiirane 1-oxides can be determined by H NMR experiments in chiral solvents such as (R)-(-)- -phenyl-2,2,2-trifluoroethanol. The... 

Trifluoroethanol [75-89-8J M 100.0, b 72.4°/738mm, d 1.400, pK 12.8. Dried with CaS04 and a little NaHCOa (to remove traces of acid). Highly TOXIC vapour. 

The greater positive character, hence the increased acidity, of the O—FI proton of 2,2,2-trifluoroethanol can be seen in the electrostatic potential maps displayed in Figure 1.8. 

FIGURE 1.8 Electrostatic potential maps of ethanol and 2,2,2-trifluoroethanol. As indicated by the more blue, less green color in the region near the OH proton in 2,2,2-trifluoroethanol, this proton bears a greater degree of positive charge and is more acidic than the OH proton in ethanol. 

The reaction mixture comprising 2,2,2-trifluoroethyl vinyl ether, 2,2,2-trifluoroethanol and potassium 2,2,2-trifluoroethylate was fractionally distilled, whereupon crude 2,2,2-trifluoroethyl vinyl ether was obtained which boiled at 42° to 45°C at 760 mm. More 2,2,2-trifluoroethyl vinyl ether was obtained when the distillation residue was returned to the bomb and reacted with acetylene in the same manner as hereinabove described. 

The alkali metal hydroxides, instead of the alkali metals per se, can be employed to produce the alkali metal 2,2,2-trifluoroethanolate. However, this introduces water in the reaction mixture which requires removal prior to vinylation with acetylene. The crude products, on further distillation, yielded 2,2,2-trifluoroethyl vinyl ether having a boiling point of 43.1°C at 759 mm. 

Compounds with a smaller/C., and larger pKa are less acidic, whereas compounds with a larger/Ca and smaller plsimple alcohols like methanol and ethanol are about as acidic as water but substituent groups can have a significant effect, tert-Butyl alcohol is a weaker acid, for instance, and 2,2,2-trifluoroethanol is stronger. Phenols and thiols, the sulfur analogs of alcohols, are substantially more acidic than water. 

Inductive effects (Section 16.4) are also important in determining alcohol acidities. Electron-withdrawing halogen substituents, for example, stabilize an alkoxide ion by spreading out the charge over a larger volume, thus making the alcohol more acidic. Compare, for example, the acidities of ethanol (p/tcrt-butyl alcohol (p/

More surprising, in view of its poor electrophilic character, is that phcnylnitrene, generated by deoxygenation of nitroso benzene with triethyl phosphite in a mixture of benzene and 2,2,2-trifluoroethanol, yields 1-phenyl-1//-azepine (26), a rare example of a stable 1-aryl-lH-azepine.170... 

Reaction constants pF and pR with opposite signs (but only small differences in magnitude) were later found for dediazoniation in 1,2-dichloroethane (Nakazumi et al., 1987), in 2,2,2-trifluoroethanol (Ravenscroft and Zollinger, 1988), and with 18-crown-6 ether complexes of substituted benzenediazonium ions (Nakazumi et al., 1987). The dediazoniation of substituted phenylazides (forming nitrenes) also... 

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