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Reaction of periodic acid on the difructose anhydrides
64
N A T I O N A L ~,UREAU OV ~TANI)ARDS NOTES.
[J. i;. 1-
DISSOCIATION CONSTANTS CALCULATED FROM ULTRAVIOLET SPECTRA.
Most organic c o m p o u n d s t h a t are colorless in the visible region of the spectrum, have absorption bands in the ultraviolet. Spectrophotometric measurements in the ultraviolet ranges have now been obtained with such accuracy that the dissociation constants of weak electrolytes can be calculated. In the December n u m b e r of the Journal of Research (RPI686), Elizabeth E. Sager, Marjorie R. Schooley, Alice S. Carr, and S. F. Acree report results on solutions of p-hydroxybenzoic acid, several of its esters, and potassium p-phenolsulfonate at 25 ° ('. by this method. The absorption bands of the ionic and the molecular forms of each c o m p o u n d were first obtained, with the use of acid, alkali, or buffers of widely different pH values. Several intermediate steps in the transformation of one form into the other were then measured. The pH of each solution was controlled by buffers of low ionic strengths, of known pH values, at each step in the transformation. From the spectral transmittancies at one or several wave-lengths, the a m o u n t s of the molecular and ionic forms can be calculated. When the pH of the buffered solution is known, the apparent dissociation constant, or pK*, can then be determined. The pK* values of methyl, ethyl, n-butyl, and benzyl p-hydroxybenzoate are all approximately 8.3. The pK* values for the first and second steps in the dissociation of p-hydroxybenzoic acid were found to be 4.5 and 9-3. The estimated values of pK~, the negative logarithm' of the t h e r m o d y n a m i c dissociation constant, for potassium p-phenolsulfonate is 9.o3. This value is o.o2 of a unit lower than the value found by e.m.f, studies. REACTION OF PERIODIC ACID ON THE DIFRUCTOSE ANHYDRIDES.
AS set forth in a report by E m m a J. McDonald and the late Ricl~ard F. Jackson in the December Journal of Research (RPI683), the di/ructose anhydrides have been reacted with periodic acid. In keeping. with their known structures, difructose anhydrides III and I react, respectively, with one and two moles of acid. Difructose anhydride II reacts with one mole of periodic acid ; thus it contains only two a d j a c e n t carbons carrying free hydroxyl groups. From this fact, along w i t h previously determined data, it is suggested t h a t 1,2'-2,4'-difructo-. furanose is the most probable structure for difructose anhydride II. T H E R M O D Y N A M I C P R O P E R T I E S OF ACETYLENE HYDROCARBONS.
T h e December n u m b e r of the Journal of Research contains a report (RPI682) entitled, "Heats, Equilibrium Constants, and Free Energies of Formation of the Acetylene Hydrocarbons through the Pentynes, to
N A T I O N A L ~,UREAU OV ~TANI)ARDS NOTES.
[J. i;. 1-
DISSOCIATION CONSTANTS CALCULATED FROM ULTRAVIOLET SPECTRA.
Most organic c o m p o u n d s t h a t are colorless in the visible region of the spectrum, have absorption bands in the ultraviolet. Spectrophotometric measurements in the ultraviolet ranges have now been obtained with such accuracy that the dissociation constants of weak electrolytes can be calculated. In the December n u m b e r of the Journal of Research (RPI686), Elizabeth E. Sager, Marjorie R. Schooley, Alice S. Carr, and S. F. Acree report results on solutions of p-hydroxybenzoic acid, several of its esters, and potassium p-phenolsulfonate at 25 ° ('. by this method. The absorption bands of the ionic and the molecular forms of each c o m p o u n d were first obtained, with the use of acid, alkali, or buffers of widely different pH values. Several intermediate steps in the transformation of one form into the other were then measured. The pH of each solution was controlled by buffers of low ionic strengths, of known pH values, at each step in the transformation. From the spectral transmittancies at one or several wave-lengths, the a m o u n t s of the molecular and ionic forms can be calculated. When the pH of the buffered solution is known, the apparent dissociation constant, or pK*, can then be determined. The pK* values of methyl, ethyl, n-butyl, and benzyl p-hydroxybenzoate are all approximately 8.3. The pK* values for the first and second steps in the dissociation of p-hydroxybenzoic acid were found to be 4.5 and 9-3. The estimated values of pK~, the negative logarithm' of the t h e r m o d y n a m i c dissociation constant, for potassium p-phenolsulfonate is 9.o3. This value is o.o2 of a unit lower than the value found by e.m.f, studies. REACTION OF PERIODIC ACID ON THE DIFRUCTOSE ANHYDRIDES.
AS set forth in a report by E m m a J. McDonald and the late Ricl~ard F. Jackson in the December Journal of Research (RPI683), the di/ructose anhydrides have been reacted with periodic acid. In keeping. with their known structures, difructose anhydrides III and I react, respectively, with one and two moles of acid. Difructose anhydride II reacts with one mole of periodic acid ; thus it contains only two a d j a c e n t carbons carrying free hydroxyl groups. From this fact, along w i t h previously determined data, it is suggested t h a t 1,2'-2,4'-difructo-. furanose is the most probable structure for difructose anhydride II. T H E R M O D Y N A M I C P R O P E R T I E S OF ACETYLENE HYDROCARBONS.
T h e December n u m b e r of the Journal of Research contains a report (RPI682) entitled, "Heats, Equilibrium Constants, and Free Energies of Formation of the Acetylene Hydrocarbons through the Pentynes, to