The value of An at 27°is a measure of the amount of decomposition product still gaseous at room temperature. The fact that An at 27°is still large, in many cases, indicates that at least some of the decomposition products are of low molecular weight. The nature of the volatile decomposition products for certain of these compounds is currently being investigated. The results of this study will be reported in a later paper.The nature of the solid residues obtained from the decomposition of the acetylacetonates was not determined. In general the change in appearance of the chelates paralleled the extent of decomposition, as indicated by An. Those acetylacetonates undergoing extensive decomposition generally gave very dark colored, and frequently resinous, residues. It is planned to study the nature of some of these materials.Acknowledgment.-The authors are grateful to Miss . I. Mistrik for certain of the analyses.
The coordination of 1,3-diamino-2-propanol (BOH) with copper(I1) ion is unique in that fz (the average number of ligands bound per ion) appears to be l : L 1 Two possible explanations of such an anomalous value are indicated in the equations ~C U + + + 3BOH J r Cuz(BOH)a*+ (1) ~C U + + + 3BOH 2Cu(BO) + + HzBOH2+ (2) The second is suggested by the isolation2 of compounds containing a complex of the formula Cu-(BO)z+. The system has been investigated in dilute solution by methods previously described and earlier findings confirmed. Calculations on the basis of the first equation did not yield constant values while those based on the second equation did. Method ofCalculation.-If V = volume of solution being titrated at any given point, V i = the initial volume of solution, Ccu++ and CH+ = concentration of Cu++ and H + in the initial solution, and CA = concentration of the amine solution added, then the equation for the H + balance in the system Cu++ (3) andThe numerator of this expression is evaluated with the use of f z~, the average number of protons bound per uncoordinated ligand (5) and the result into (4) yieldsThis equation may be rearranged to the formEquation 7 now contains the quantity originally used to calculate FZ on the assumption that a simple, step-wise process was occurring. If we call this quantity FZB and recognize that FZA = 2 throughout the pH range of chelation, then equation 7 becomes (1) E. Gonick, W. C . Fernelius and B. E. Douglas, J. Am. Chem. (2) J. G . Breckenridge and J. W. Hodgins, Can. J. Ressarch, 17, 331 SOC., 17, 6506 (1955). (1939). However, if we assume that CuBO+ is the only coordinated species present V[CuBO +] E = ViCcut+ and equation 8 can be converted toThis results in a maximum ii of 1 rather than the anomalous value of 1.5 previously reported, a result which is consistent with the assumption that CuBO + is the only coordinated species present.The calculation of [BOH] from equation 3 requires the elimination of [CuBO+]. Since BA remained a t 2 throughout the chelation range, the concentrations of BOH and HBOH+ are small, and all the 1,3-diamino-2-propanol is essentially present as either CuBO+ or HzBOH++. Consequently and equation 3 becomescA (11) [H2BOH++] is the only unknown in equation 11 and may therefore be calculated directly. From this concentration [CuBO+] follows from equation 10 and [BOH] and [HBOH+] from the proton-l,3-diamino-2-propanol constants reported elsewhere.* The values found are negligible with respect to [Cu-BO+] and [H2BOH+] and validate the assumptions made. The remaining concentration, [Cu++], needed in order to calculate the equilibrium constant for Cu++ + BOH CuBO+ + H + (12) follows from ViCcu++ = ([Cu++] + [CuBO+])V. Results and DiscussionThe values of this constant over the temperature range 10-40°, with 95'%-confidence intervals based on a t least three independent calculations, and the thermodynamic quantities derived from them are presented in Table I.
The amylopectin acetate molecule has an average molecular weight of 107 with approximately 1300 branches,7 and it is therefore expected that chain entanglement is present. Chain segments are possibly unraveled by dipole-dipole interaction with plasticizer molecules, the extent increasing with the increasing polarity of the plasticizer molecules.
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