The Endochronic Properties of Resublimated Thiotimoline
The correlation of the structure of organic molecules with their various properties, physical and chemical, has in recent years afforded much insight into the mechanism of organic reactions, notably in the theories of resonance and mesomer-ism as developed in the last decade. The solubilities of organic compounds in various solvents has become of particular interest in this connection through the recent discovery of the endochronic nature of thiotimoline.
It has been long known that the solubility of organic compounds in polar solvents such as water is enhanced by the presence upon the hydrocarbon nucleus of hydrophilic - i.e., water-loving - groups, such as the hydroxy (-OH), amino (-NH2), or sulfonic acid (SO3H) groups. Where the physical characteristics of two given compounds - particularly the degree of subdivision of the material - are equal, then the time of solution - expressed in seconds per gram of material per milli-liter of solvent - decreases with the number of hydrophilic groups present. Catechol, for instance, with two hydroxy groups on the benzene nucleus, dissolves considerably more quickly than does phenol, with only one hydroxy group on the nucleus. Feinschreiber and Hravlek in their studies on the problem have contended that with increasing hydrophilism, the time of solution approaches zero. That this analysis is not entirely correct was shown when it was discovered that the compound thiotimoline will dissolve in water - in the proportions of 1 gm./ml. - in minus 1.12 seconds. That is, it will dissolve before the water is added.
Previous communications from these laboratories indicated thiotimoline to contain at least fourteen hydroxy groups, two amino groups and one sulfonic acid group. The presence of a nitro group (-NO2) in addition has not yet been confirmed, and no evidence as yet exists as to the nature of the hydrocarbon nucleus, though an at least partly aromatic structure seems certain of solution of thiotimoline quantitatively met with considerable difficulty because of the very negative nature of the value. The fact that the chemical dissolved prior to the addition of the water made the attempt natural to withdraw the water after solution and before addition. This, fortunately for the law of Conservation of Mass-Energy, never succeeded, since solution never took place unless the water was eventually added. The question is, of course, instantly raised as to how the thiotimoline can 'know' in advance whether the water will ultimately be added or not. Though this is not properly within our province as physical chemists, much recent material has been published within the last year upon the psychological and philosophical problems thereby posed.
Nevertheless, the chemical difficulties involved rest in the fact that the time of solution varies enormously with the exact mental state of the experimenter. A period of even slight hesitation in adding the water reduces the negative time of solution, not infrequently wiping it out below the limits of detection. To avoid this, a mechanical device has been constructed, the essential design of which has already been reported in a previous communication.6 This device, termed the endochronometer, consists of a cell 2 cubic centimeters in size into which a desired weight of thiotimoline is placed, making certain that a small hollow extension at the bottom of the solution cell - 1 millimeter in internal diameter - is filled. To the cell is attached an automatic pressure micro-pipette containing a specific volume of the solvent concerned. Five seconds after the circuit is closed, this solvent is automatically delivered into the cell containing the thiotimoline. During the time of action, a ray of light is focused upon the small cell-extension described above, and at the instant of solution, the transmission of this light will no longer be impeded by the presence of solid thiotimoline. Both the instant of solution - at which time the transmission of light is recorded by a photoelectric device - and the instant of solvent addition can be determined with an accuracy of better than 0.01 %. If the first value is subtracted from the second, the time of solution (T) can be determined.
The entire process is conducted in a thermostat maintained at 25.00° C. - to an accuracy of 0.01 ° C.
Thiotimoline Purity - The extreme sensitivity of this method highlights the deviations resulting from trifling impurities present in thiotimoline. (Since no method of laboratory synthesis of the substance has been devised, it may be practically obtained only through tedious isolation from its natural source, the bark of the shrub Rosacea Karlsbadensis rugo.) Great efforts were therefore made to purify the material through repeated recrystallizations from conductivity water - twice redistilled in an all-tin apparatus - and through final sublimations. A comparison of the solution times (T) at various stages of the purification process is shown in Table I.