Complex fluoroanions have been prepared with boron trifluoride and perchlorate, nitrate, nitrite, acetate, formate, azide, cyanide, cyanate, thiocyanate, and thiophenolate ions. The complexes formed from the anions of the strong acids, except the hydrogen halides, do not disproportionate to BF2(anion)2−. Complexes of anions of weaker acids may disproportionate and, or, complex a second molecule of BF3. Regularities in fluorine–boron coupling constants are tabulated.

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The rates of reaction of halide ions with ethylene oxide in neutral aqueous solution and the rate of hydrolysis of ethylene oxide in acid solution have been measured and the activation energies determined. From these data and from the ratio of glycol to chlorohydrin formed when ethylene oxide reacts with excess aqueous hydrogen halide, the rates of the acid-catalyzed addition of halide ions to ethylene oxide a t 25°C. have been estimated.

Accurate and convenient analyses for ethylene oxide can be obtained using 1% periodic acid in dilute perchloric acid as reagent. The time required is less than an hour and the precision is about 0.1–0.2%.

Studies of the boron-fluoride-catalyzed reaction of ethylene oxide with simple alcohols and low molecular weight polyglycols indicate three ways in which chain growth could occur, but only one of these is considered to be important after the initial stages of polymerization. The rate of disappearance of monomer reaches a maximum a t a molecular weight of about 400. A mechanism is proposed to account for both polymerization and depolymerization and it is shown how equilibrium between these two reactions could result.The polymerization of ethylene oxide by boron fluoride is a complex process in which the propagation reaction must compete with an appareiltly independent depolymerization reaction. The depolymerization process, as discussed in the previous paper (I), breaks down the polyglycol to dioxane seemingly through a chain reaction propagated by oxonium ions acting upon the ether linkages in the polymer molecule. The polymerization on the other hand appears to occur through a stepwise addition of monomer to the terminal hydroxyls of the polymer chain. A study was therefore undertaken of the reaction of ethylene oxide with alcohols in the presence of boron fluoride in an effort to obtain a mechanism for the propagation and t o observe the transition fro111 propagation to depolymerization. This paper presents the results of these studies.. EXPERIMENTALEthylene chloride, ethylene oxide, and boron fluoride were prepared for use as previously described (2). Volatile alcohols were dried by distillation froill their magnesium alcoholates in the usual way and ethers were dried over sodium metal or calcium hydride, \ZTherever the reactants were sufficiently volatile they were stored on the vacuum system and transferred by distillation. T h e polyglycols were either stirred under high vacuum for several hours or dissolved in dry ethylene chloride and pumped free from solvent before use. Molecular weights were determined by viscosity ineasureme~lts as before, but in a few cases were confirined by freezing point depressions in benzene. Where hydroxyl content of the polynler was important, end group analysis by acetylation with acetyl chloride in pyridine, according to the nlethod of Smith and Bryant (3), was used. All three methods gave satisfactory agreement.Reactions were carried out in ethylene chloride solution a t 20° C. Rates were followed either by the decrease in vapor pressure of ethylene oxide as described in the earlier work, or by a dilatometric method. The dilatometers were so constructed that they could be dried and filled under vacuunl and then transferred to a constant temperature bath while exposing only the capillary tip t o the atmosphere. Absolute contractions were not determined but the contraction per unit of oxide appeared t o be constant over the range of the experiments. The two methods gave good agreement wherever they could be compared. 'Manuscript