The infrared spectra of concentrated performic and peracctic acids were measured in the rock-salt region. The most significant features are theO-Hstretching frequency a t 3310-3350 cm.-1 and the O H bending frequency a t 1450 cm.-1 which, for both peracids, remain essentially the same in the vapor state a s in the liquid or in solution in nonpolar solvents. This is attributed to i~~tramolecular hydrogen bonds resulting in particularly stable five-membered rings, 0 .Steric conditions in the percarboxylic group are favorable to such ring formation or chelatiotz. From the observed freqi~ency shifts the energy of these hydrogen bonds is estimated to be about 7 kcal. per mole. No evidence for unchelated molecules was found even in very dilute solutions of peracetic acid in nonpolar solvent nor in the vapor a t low pressure and moderate temperature. Tentative assignments of the other freqiiencies i n the spectra of the peracids are made by comparison with those of formic and acetic acids.The danger involved in handling these peracids in concentrated form is emphasized.

The heat of mixing of hydrogen peroxide and water and the heat of vaporization of the mixtures were measured over a wide concentration range a t O0 C. with a Bunsen ice calorin~eter and a t 26.V with a diphenyl ether calorimeter. The heat capacities of the solutions were determined between these two temperatr~res. Similar measurements were carried out on the corresponding deuterium compounds. The heat of decompositio~l of hydrogen peroxide catalyzed by colloidal platinum was also measured a t 2G.D0 as a function of concentration. Correlatioil of all the results leads to the following recommended values for the therrnochemical properties of the pure peroxides in the liquid state a t 25' C. 1320.n,o,

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.qBSTR-kCT The need for a Bunsen-type isothermal calorimeter operating as close as possible t o the standard thermochemical reference temperature, 2j°C., was fulfilled by means of diphenyl ether (m.p. 26.n0C.) as the working substance. The instrument was calibrated electrically by comparison with the ice calorimeter arid the constant was found to be 19.01+0.02 cal. per gm. of mercury. From this and other lcnown properties of diphenyl ether the density of the solid a t the melting point was estimated a t 1.188 gm. per mI. Check determinations based on the heat of vaporization of water showed that for such measurements the mantle of solid ether must first be melted inside by a n amount equivalent to the heat t o be measured. The calorimeter was operated in a large water-thermostat kept constant to within O.OOI°C. With highly purified diphenyl ether there was no noticeable temperature drift during the measurements. Quantities of heat up to GOO cal. could be measured with a reproducibility of the order of 0.2%. The new calorimeter is simpler to operate than the ice calorimeter and its sensitivity is more than three times as great.

Oxidation O 0212Oxidation of Alcohols to Carbonyl Compounds with CrO 3 ·SiO 2 in Supercritical Carbon Dioxide. -The products are obtained in good to high yields without any significant contamination with chromium species. However, alcohols containing distant double bonds sometimes undergo side reactions. -(GONZALEZ-NUNEZ, M. E.; MELLO, R.; OLMOS, A.; ACERETE, R.; ASENSIO*, G.; J. Org. Chem. 71 (2006) 3,