Volatility of the catalytic hydrogenation products of 1,4 bis(phenylethynyl)benzene

Abstract

Measurements of equilibrium vapor pressures by effusion thermogravimetry and melting points by differential scanning calorimetry reveal that the melting temperature and equilibrium vapor pressures of 1,4-bis(phenylethynyl)benzene (DEB) do not vary monotonically with the hydrogenation extent. Contrary to intuition which suggests increasing volatility with hydrogenation, results indicate decreasing volatility for the first two hydrogenation steps before a non-monotonic upward trend, in which trans-isomers are less volatile. Insights on structural packing and functional groups were obtained from x-ray diffraction and infrared studies to shed light on the observed variation in the volatility of DEB with hydrogenation. Density functional theory calculations were performed to obtain molecular level information and to establish the thermodynamics of DEB hydrogenation reactions. A major factor influencing the observed melting points and volatility of the hydrogenated intermediate species is identified as the local attractive or repulsive carbon-hydrogen (CH) dipole interactions among the getter molecules in their respective crystal structures. Such collective CH dipole interactions can be used to predict the trends in the volatilities of catalytic hydrogenation processes.

Thermal reactions involving solids: a personal view of selected features of decompositions, thermal analysis and heterogeneous catalysis

“…The articles [47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64], identified in my literature search as most likely to contain references to CDV theory, revealed only a single meaningful example [53]. Nine others [54,55,[57][58][59][60][61][62][63] cite articles critical of Thermoanalytical Studies, TAS, mainly [27,28] four each, [3,43] one each, and six refer to several of L'vov's articles.…”

“…Seemingly 'TAS' researchers have worked to their own set of rules, a conclusion supported by the fact that criticisms of these 'rules', levelled by this author and others [18][19][20][21][22][23][24][25][26][27][28], have been repeatedly ignored. A survey of more recent publications that include citations [47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64] of these critical articles shows that little, usually no, notice has been taken, nor have any 'answers' been attempted. The same ignorant, uncouth attitude has applied to the novel L'vov thermochemical CDV approach to solid-state decompositions [29,30].…”

“…Calculations reported to excessive decimal places cannot increase data accuracy! Survey of contents of articles [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64], all citing references in references [18][19][20][21][22][23][24][25][26][27][28][29][30] (The initiative for this analysis is explained in Acknowledgements at the end of the article). Over three decades, articles [18][19][20][21][22][23][24][25][26][27][28][29][30] detailing the many shortcomings, limitations, errors, misconceptions, etc., typical and characteristic of Thermoanalytical Studies, TAS, were published.…”

“…The content of these articles justifies and exemplifies the generalisations, made in this review, about the lack of responses to criticisms. This section surveys the more recent literature [47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64] to assess any later impact of these same criticisms. The conclusion is that all these censures and the novel, alternative theory, the thermochemical (CDV) approach, remain effectively ignored.…”

“…The contents and relevance of the other eighteen [47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64] articles to the criticisms levelled against Thermoanalytical Studies, TAS, are briefly commented upon and appraised below: [47] Reference [18] is cited but CDV theory is not, cannot be, used in this largely empirical kinetic analysis of cassava starch degradation, for which both rate equation and E show variations.…”