The system of bond and group energies described in Part I has been extended and applied to certain compounds containing sulphur and oxygen. The substances treated are the alkanethiols, the thiaalkanes, and the dithiaalkanes. The bond additivity scheme enables reliable values for heats of formation, combustion, atomization, and vaporization to be calculated for these compounds.X similar treatment has been applied t o the data for alcohols, ethers, and alkyl peroxides. INTRODUCTIONlnrPart I of this series (I) a scheme of bond and group energies, suitable for the reliable calculatioll of heats of formation, comb~~stion, and atomization of organic compounds, was developed. The method was applied in some detail to the paraffins, olefins, and acetylenes. For other con~pounds adeq~iate data for l~omologo~is series were not available, and only approximate group contributions could be obtained. A method n-hereby the scheme could be extended to substituted homologous series, when sufficient reliable data became available, was also given. During the past few years excellent data have become available for alkanethiols (R-S-I-I), thiaalkanes (R-S-R), and dithiaallranes (R-S-S-R), and in the present paper the scheme is applied to these. X few recent data are also available for certain alcohols, ethers, and peroxides, and the scheme has bee11 extended to cover these compounds also.The previous paper also provided a scheme for the calculation of heats of vaporization,and it is applied in the present worlr to the sulphur compounds mentioned above. HEATS O F FORMATION, COMBUSTION, A N D ATOMIZATIONThe heat of atomization is the energy required to dissociate 1 mole of a compound, in the gaseous state, into its constituent atonls in their ground states. The heats of atomization given in this paper are calculated with the aid of the following relationships, which apply a t 25.0' C:The choice of the first three values was discussed in Part I. The value for the heat of sublimatio~l of rhombic sulphur has not bee11 firmly established. Cottrell (3) has recently reviewed the chemical and spectroscopic evidence, on the basis of which he favors the value of 57 lrcal. We have chosen to use this value in the present paper.Based up011 the above relations, the heat of atomization, Q,, of compounds containing carbon, hydrogen, sulphur, and oxygen is obtained throughlthe equation 'Manuscript received August 8, 1960. Contribution from the Departtnent of Chemistry, University of Ottawa, Ottawa, Ontario.Can. J. Chem. Val. 38 (1960) Can. J. Chem. Downloaded from www.nrcresearchpress.com by 54.191.190.102 on 05/12/18For personal use only.

The kinetics of 12 alco21ol-isocyanate reactions have been studied a t a series of temperatures. The reactions were studied by a calorimetric technique, as well as the usual analytical method. The results are shown to be in agreement with a mechanism previously proposed by Baker. Certain objections to Baker's mechanism are discussed.

The X‐ray procedure for estimation of the degree of crystallinity in digoxin is based upon measurement of the total X‐ray scattering and the scattering from crystalline regions of the drug. The infrared procedures are based upon measurement of the peak height ratios, 1775/1618 and 3095/1618 cm−1. Correlation between results obtained by the two methods is good. These methods are of value in the physico‐chemical characterization of digoxin, particularly as the properties may be altered by comminution.

The melting transitions of both crystalline forms of trans‐1,4‐polyisoprene, as detected by differential thermal analysis, have been identified by attendant studies with optical microscopy and x‐ray diffraction. The lower‐melting (LM) form melts initially at a temperature which depends upon the crystallization temperature but which, under our experimental conditions, is between 45 and 53°C. If recrystallization is allowed to occur, the apparent final melting point, which depends upon the recrystallization temperature, is about 58°C. The initial melting point of the higher‐melting (HM) form, also crystallization temperature‐dependent, is upwards of 57°C. Under the most easily accessible experimental conditions, it may be obscured by the final melting of the LM‐form. The apparent final melting point of the HM form is approximately 66°C. Conversion of the LM form into the HM form occurs only by fusion and crystallization. No evidence of a solid‐solid transition was found. The rate of conversion is governed principally by the rate of nucleation at the conversion temperature. If fusion of the LM form is incomplete, recrystallization of the LM form takes place instead of conversion to the HM form.

Liquid chromatographic (LC) methods have been developed for the determination of carbamazepine, the impurity 10,11-dihydrocarbamazepine, and related compounds in carbamazepine drug substance and tablets. The LC methods specify a 5 jxm diol column and a mobile phase of acetonitrile-methanol-0.05% aqueous acetic acid (5 + 5 + 90). Iminodibenzyl and iminostilbene, starting materials for some routes of synthesis, elute late in the LC system; therefore, a thinlayer chromatographic method for their detection at the 0.05% level has been developed. Eight tablet and 13 raw material samples from several sources were examined. The impurities most frequently found were 10,11-dihydrocarbamazepine and a compound identified as 10- bromocarbamazepine at levels up to 1.3 and 0.5%, respectively; minimum detectable amounts were about 0.01 and 0.03%, respectively.