Dehydration, under vacuum, of magnesium sulphate heptahydrate yields a product of monohydrate composition which does not give a diffraction pattern on X-ray examination and therefore has no evident crystalline structure. The heat capacity of this product has been determined over the temperature range from 90°K. to room temperature, and has been found to be substantially higher than that of the normal crystalline monohydrate. Consideration of these differences in heat capacity in conjunction with surface area data indicates that vacuum dehydration does not result in the formation of microcrystals the surfaces of which are available for gas adsorption. It is possible that aggregates of closely packed crystallites are formed in localized regions, these being interspersed with capillaries. Alternatively, it is possible that vacuum dehydration results in an intermediate state of ionic disorder.

One major goal of organometallic chemists is the direct functionalization of the bonds most recurrent in organic molecules: C-H, C-C, C-O, and C-N. An even grander challenge is C-C bond formation when both precursors are of this category. Parallel to this is the synthetic goal of achieving reaction selectivity that contrasts with conventional methods. Electrophilic aromatic substitution (EAS) via Friedel-Crafts acylation is the most renowned method for the synthesis of aryl ketones, a common structural motif of many pharmaceuticals, agrochemicals, fragrances, dyes, and other commodity chemicals. However, an EAS synthetic strategy is only effective if the desired site for acylation is in accordance with the electronic-controlled regioselectivity of the reaction. Herein we report steric-controlled regioselective arene acylation with salicylate esters via iridium catalysis to access distinctly substituted benzophenones. Experimental and computational data indicate a unique reaction mechanism that integrates C-O activation and C-H activation with a single iridium catalyst without an exogenous oxidant or base. We disclose an extensive exploration of the synthetic scope of both the arene and the ester components, culminating in the concise synthesis of the potent anticancer agent hydroxyphenstatin.

Rates of dehydration under vacuum, and a t a series of controlled water vapor pressures, have been carried out for powdered samples of magnesium sulphate heptahydrate and of cobaltous chloride hexahydrate. I t has been found for the magnesium salt that as the pressures are increased, the rate a t first drops rapidly, this decrease being followed by a period of acceleration which is followed in turn by a decline. The curves are similar to those previously reported for copper sulphate pentahydrate, but the changes occur over a much wider range of water vapor pressures. In the dehydration of cobaltous chloride hexahydrate the initial drop in rate with increase in water vapor pressure is not observed. The results are interpreted in terms of the crystallization of intermediate products in the presence of adsorbed water.

The rate of dehydration of copper sulphate pentahydrate has been determined over a range of low pressures of water vapor. I t has beer1 found that a s the pressures are increased, the rate a t first drops very rapidly; this drop is followed by a period of marked acceleration, whicli is followed in turn by a gradual decline. Copper sulphate pentahydrate has bee11 found to be similar in this respect t o manganous oxalate dihydrate, which has been hitherto regarded as unique in its behavior. The observed effects are pro.bably due to amorphous to crystalline transitions occurring during induction periods, the durations of which have also been found to depend on water vapor pressure.

Rates of dehydration under full vacuum, and also a s the pressure of water vapor due to the dehydration process was allowed to increase, have been determined for a number of hydrated salts. The dehydration of manganous sulphate tetrahydrate, zinc sulphate heptahydrate, nickel sulphate hexahydrate, and magnesium sulphate heptahydrate has been found to proceed through the formation of amorphous intermediates, the last two of these being very stable. The dehydration of nickel nitrate hexahydrate, magnesium nitrate hexahydrate, and probably of ferrous sulphate heptahydrate and cobalt chloride hexahydrate a t very low pressures takes place with the formation of crystalline intermediates. The results obtained are discussed in relation to the dependence of rate of dehydration on water vapor pressure previously reported for copper sulphate pentahydrate and for manganous osalate dihydrate. INTRODUCTIONI t has been shown in an earlier paper (3) that when powdered samples of copper sulphate pentahydrate are dehydrated under vacuum a t moderate temperatures, the dehydration proceeds to the monohydrate stage with a gradual decrease in rate. The product is amorphous in the sense that it does not diffract X-rays. However, if similar samples are placed in a closed and initially evacuated space, and the water vapor pressure due to the dissociation of the hydrate allo\ved to increase in the vessel, the rate of dehydration a t first decreases to a minimum value, then increases to a value much larger than the minimum rate, this being followed, in turn, by a decline. The end product formed under these conditions is cryst a 11' ine.The minimum in rate occurs a t a water vapor pressure of approximately 0.25 mm. and the periods of acceleration and decline, over a range in pressure of only a few millimeters, these pressures being far below those corresponding to possible phase equilibria. This marked effect of water vapor in a very narrow region of pressure has been observed also by carrying out dehydrations a t a series of controlled pressures. The dehydration curves obtained for pressures below 0.25 mm. are quite different than for those above this value, the former showing a gradual loss in weight with time, while the latter show induction periods, the duration of which depends on the pressure.The behavior of copper sulphate pentahydrate in this respect is similar to that of manganous oxalate dihydrate (6,7), which for many years was regarded as unique in the dependence of its rate of dehydration on water vapor pressure. On vacuum dehydration this salt hydrate also yields a product which does not diffract X-rays.Explanations of the form of these rate curves have been discussed elsewhere (1, 3, 4). The initial fall in rate is probably due to the retarding effect of water lillanz~script received Novenzber 16, 1954.