Heat of hydrogenation table

Aryl azides react with olefins to give 1,2,3-A2-triazolines.201-203 Whereas unactivated olefins are sluggish toward aryl azides, strained bicyclic systems, on the contrary, are particularly reactive.204-208 The rate of phenyl azide addition to a series of olefins parallels the heat of hydrogenation (Table Vffl).107 This thermodynamic parameter is a measure for the degree of strain associated with these molecules.200 Bicyclo[2.2.1]hep-tenes, such as norbomene (37), react readily at room temperature, and the addition occurs at the less hindered exo side (39).,06 1°7 210 211 A striking example of the increased... 

It follows that the ratio 0ob../Sc k.. may be taken as giving directly the fraction of part 1 characterized by higher adsorption heat of hydrogen. Table II shows the ratio x for reduced iron and for tungsten, respectively. 

Evidence for the extra stability of conjugated dienes comes from mea surements of heats of hydrogenation (Table 14.1). We saw earlier inthedit cussion of alkene stabilities (Section 6.7) that alkenes of similar substitution pattern have remarkably similar AHgydrog values. Monosubstituted alkenes such as 1-butene have values for near -126 kJ/mol... 

The purpose of this section is to provide an overview of the principal kinetic features of the hydrogenation of ethene and of propene, as providing a framework (or at least part of one) within which discussion of mechanisms must be conducted. Their reactions with hydrogen (and with deuterium) are quite comparable the addition of the methyl group leads to somewhat higher reactivity, due to weaker chemisorption as might be predicted from its lower heat of hydrogenation (Table 7.1). Relative rates for other alkenes will be considered later. The problem of deactivation by carbon deposition has already been mentioned, but quantitative... 

Use these data to calculate the energy difference between cis- and fra/ s-2-butene. How does this energy difference compare to that based on heats of hydrogenation (Table 6.1) and heats of combustion (Figure 5.3) ... 

The heats of formation of most organic com pounds are derived from heats of reaction by arith metic manipulations similar to that shown Chemists find a table of AH values to be convenient because it replaces many separate tables of AH° values for indi vidual reaction types and permits AH° to be calcu lated for any reaction real or imaginary for which the heats of formation of reactants and products are available It is more appropriate for our purposes however to connect thermochemical data to chemi cal processes as directly as possible and therefore we will cite heats of particular reactions such as heats of combustion and heats of hydrogenation rather than heats of formation... 

Heats of hydrogenation can be used to estimate the stability of double bonds as structural units even m alkenes that are not isomers Table 6 1 lists the heats of hydro genation for a representative collection of alkenes... 

Table 14.1 Heats of Hydrogenation for Some Alkenes and Dienes...

Heat of combustion, 113 Heat of hydrogenation, 186 table of, 187 Heat of reaction, 154 Helicase, DNA replication and, 1106 Hell-Volhard-Zelinskii reaction, 849 amino acid synthesis and. 1025 mechanism of, 849 Heme, biosynthesis of, 966 structure of, 946 Hemiacetal, 717 Hemiketal, 717 Hemithioacetal, 1148 Henderson-Hasselbalch equation,... 

For a review of heats of hydrogenation, with tables of values, see Jensen, J.L. Prog. Phys. Org. Chem., 1976, 12, 189. 

The heats of hydrogenation of the olefins are derived from measured heats of hydrogenation by Kistiakowsky and co-workers (see also Ref. 43). Those of the dienes have been obtained from heats of formation of butadiene and of isoprene and the heats of formation of the corresponding mono-olefins Heats of hydrogenation of the last four monomers listed in the table are from direct measurements by Kistiakowsky and co-workers. ... 

The heats of polymerization of various monomers calculated from measured heats of hydrogenation and values for AJ e estimated in this manner are given in Table XXV. ... 

When we look at the energies from Table 15. 10, perhaps the most striking fact is that the correlation energy in the n system makes so little difference in the Ai values. As we indicated above, the experimental value for the resonance energy from heats of hydrogenation is —1.54 eV, in quite satisfactory agreement with the result in Table 15.10. The fact that our value is a little lower than the experimental one may be attributed to the small amoimt of residual resonance remaining in the cyclohexatriene, whereas the isolated double bonds in the experiment are truly isolated in separate molecules. ... 

Hazardous Reactions with Water-Reactive Materials. Accdg to Refs 1,2,3 5, w reacts with a variety of elements, compds and mixts to generate at RT either an expln or a combustion reaction because of the hydrogen released and the heat of reaction. Table 1 presents an identification of the reactants, and a generalized classification of the results of these reactions into either expln or combustion . From Ref 3, a more quantitative approach yielded data in terms of temp increase and the time required to reach the max temp on a selected group of w-reactants (Table 2). Table 3 displays the results of an attempt to determine if the order of addition (effects of dilution and/or surface... 

The heats of hydrogenation of some angle strained cycloalkynes have been determined in acetic acid150) or cyclohexane 151. The experimental values including the heats of hydrogenation of some open-chain reference substances are given in Table 5. 

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