Group thermochemical data, 490

The possibility of predicting solid state reactivity from calculated thermochemical data was first addressed with ketodiesters 65a-e, which were substituted with methyl groups to vary the extent of the RSE in the radicals 65-BRl - 65-BR3 involved along the photodecarbonylation pathway (Scheme 7.19). " All ketones reacted in solution to give complex product mixtures from radical combination (66a-e) and disproportionation processes. Calculations revealed RSEs of 8.9 kcal/mol, 15.1 kcal/mol, and 19.8 kcal/mol for radicals 65-BRl (primary enol radical), 65-BR2 (secondary enol radical), and 65-BR3 (tertiary enol radical), respectively. In the... 

The chemistry of carbenes in solution hits been extensively studied over the past few decades.1-5 Although our understanding of their chemistry is often derived from product analyses, mechanistic details are often dependent on thermodynamic and kinetic data. Kinetic data can often be obtained either directly or indirectly from time-resolved spectroscopic methods however, thermochemical data is much less readily obtained. Reaction enthalpies are most commonly estimated from calculations, Benson group additivities,6 or other indirect methods. 

This useful and simple-to-use software package relies on Benson s group additivity scheme [47] to estimate thermochemical data for organic compounds in the gas phase. It also contains values from several NIST databases, including NIST Positive Ion Energetics [32] and JANAF Tables [22]. The first version of... 

This book contains a small database for organic and inorganic compounds. Its main value, however, is that it describes a group additivity scheme to estimate thermochemical data. An updated and extended list of group parameters is given in NIST Therm [28]. The first edition of this classic work is from 1968. 

We now consider heteroaromatic diamines with the condition that an amino group is not a to a heterocyclic nitrogen. The only thermochemical data we can find are for 2,8-diamino acridine for which the solid-phase enthalpy is 127 7 kJmol-1. In the absence of significant substituent and solid state effects, thermoneutrality is expected for the conproportionation reaction 40 that produces diaminoarenes from monoamine derivatives. 

Numerous aromatic nitro compounds have explosive properties, and thus it is important to understand the role that enthalpy of formation has on the sensitivity and long-term stability of these compounds. We will examine three nitro-substituted aromatic families for which thermochemical data can be found in the literature2,84 derivatives of nitrobenzene, aniline and toluene. The choice of these three families allows us to compare the various electronic effects exerted by the parent functional group. The parent compounds differ electronically with respect to the aromatic ring in that ... 

Pedley provides group values and the experimental data from which they have been derived. J. Pedley, Thermochemical Data and Structure of Organic Compounds-Vol. /, TRC Data Series, CRC Press, Boca Raton, FL, 1994. 

Tn 1965 Benson (3) discussed the basic thermochemistry and kinetics of combustion reactions. Since then additional thermochemical data have become available and the Benson and Buss Group Additivity Tables (7) have been revised (8). 

The accepted values for the standard reduction potentials for the Group 1 unipositive cations being reduced to the solid metal are given in Table 6.4, and some thermochemical data and the appropriate ionic radii are given in Table 6.5. 

In the text, each paragraph or group of paragraphs is labeled with the formula of a chemical substance (or substances), and under that heading are cited all the published thermochemical data on reactions which can... 

NIST/CSTL/PMD Reacting Flows Group Thermochemical and Chemical Kinetic Data for Fluorinated Hydrocarbons, www.cstl.nist.gov/div836/ckmech, 2002. 

The lack of additional thermochemical data is admittedly frustrating because there are many other documented cyclopropenones [e.g., see W. E. Billups and A. W. Moorehead, in The Chemistry of the Cyclopropyl Group (Ed. Z. Rappoport), Chap. 24, Wiley, Chichester, 1987, p. 1533] which have higher stability and alternative amounts of conjugation with the affixed substituents. 

The uses of thermochemical data in estimating heats of detonation, detonation product compns, fire and expin hazards and critical diameters for expls were reviewed earlier (Vol 7, H38-L ff). For instances where heats of formation of organic expls are lacking, their estimation from group activities was described in Vol 7, H47-L ff A method for linking thermochemical data to the prediction of hazards was presented in Vol 7, HI 5-L to H23-L. The reader is directed to this article for a discussion of the complexity of the subject. For a further exposition of the problem, see Safety in the Energetic Materials Field in this Vol... 

Thermochemical data are available (Ref 2) on the heats of combustion and formation for all five isomers, on the heats of nitration from various Dinitrotoluenes for the 23,4-, 2,4,5-, and 2,3,6-isomers, and on the heats of crystn for the 2,3,4- and 2,4,5-isomers. Data are also available (Ref 1) on the shock sensitivities of all of the isomers except 2,3,6-, and on the rates of decompn at 140° of the 23,4-, 2,4,5-, and 23,5-isomers. The detonation pressure and the temp coefficient of decompn between 140 and 180° have been measured for the 2,4,5-isomer 2,3,4- and 2,4,5-TNT form addition compds ( 7r-complexes ) at 1 1 molar ratio with several polycyclic aromatic hydrocarbons (naphthalene, acenaphthene, fluorene, phenanthrene and anthracene) (Ref 2). 2,4,5-TNT forms complexes with 4-aminozaobenzene, 4-aminoacetophenone, bis (2 hydroxy ethyl) amine, and tris (2-hydroxy-ethyl) amine (Ref 1). The first two have a 1 1 molar ratio, the third 1 2, and the fourth 2 1. Upon heating, the two 4-amino compds react with replacement of the 5-nitro group, as discussed below... 

The key question for such species is whether two imine groups will provide intramolecular stabilization or destabilization. There are three examples of these species for which there are relevant thermochemical data 70a, the conjugated glyoxal bis-imine,, BuN=CI ICI I=NBu (see Reference 153) 70b, the cyclic and likewise conjugated... 

The methods available for computing enthalpies of formation fall into two general groups those based on purely empirical schemes and those founded on quantum chemistry. The quantum chemical methods can be further divided into three types ab initio molecular orbital theory, density functional theory, and semiempirical molecular orbital theory. A summary of the types of method used to calculate enthalpies of formation is given in Table 2, along with some specific examples. This is not meant to be a comprehensive tabulation, but rather a list of some of the more popular approaches in use today. Table 3 names some of the commercially available computer programs having capabilities to calculate thermochemical data. 

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