Energy value, alcohol

Reaction temperature is one of the parameters affecting the enantioselectivity of a reaction [16]. For the oxidation of an alcohol, the values of kcat/fQn were determined for the (R)- and (S)-stereodefining enantiomers E is the ratio between them. From the transition state theory, the free energy difference at the transition state between (R) and (S) enantiomers can be calculated from E (Equation 2), and AAG is in turn the function of temperature (Equation 3). The racemic temperature (% ) can be calculated as shown in (Equation 4). Using these equations, % for 2-butanol and 2-pentanol of the Thermoanaerobacter ethanolicus alcohol dehydrogenase were determined to be 26 and 77 °C, respectively. 

The hydroxyl group of alcohol weakens the a-C—H bond. Therefore, free radicals attack preferentially the a-C—H bonds of the secondary and primary alcohols. The values of bond dissociation energy (BDE) of C—H bonds in alcohols are presented in Table 7.1. The BDE values of C—H bonds of the parent hydrocarbons are also presented. It is seen from comparison that the hydroxyl group weakens BDE of the C—H bond by 23.4 kJ mol 1 for aliphatic alcohols and by 8.0 kJ mol 1 for allyl and benzyl alcohols. 

TABLE 5. NO—H bond dissociation energy values of X-aryl-substituted Ai-hydroxyphthaUmides (X-HPIs), listed with the Hammett p values (vs. ct+) and h/ d ratios obtained in the oxidation of substituted benzyl alcohols using the X-HPIs/Co(II)MCBA/02 system in MeCN solution at 25 °C... 

Besides having smaller oxidation potential values than substituted benzyl alcohols (E° > 1.4 V/NHE), the DMAs have larger energy values (90-92 kcalmoD ) for the NC—H bond with respect to C—H bond energies around 75-85 kcalmoD of the benzyl alcohols (Scheme 12). Both factors disfavour the operation of the radical HAT route for PINO with the DMAs, and cause a mechanistic changeover to the ET route, as opposed to the reactions with the benzylic substrates listed in Table 4. 

Livesey G. The energy values of dietary fibre and sugar alcohols for man. Nutr Res Rev 1992 (5) 61-84. 

Inspection of Figs. 10-2/ and g shows that the reduction of aldehydes to alcohols parallels, in many respects, that of olefins to paraffins. At 100°C, it is seen that the normal alcohols have lower free-energy values than the corresponding aldehyde. Hydrogenation is, therefore, feasible if catalysts can be found to effect the reduction with reasonable speed. At higher temperatures, e.g., 400 C, the aldehyde is seen to possess a lower free-energy vSlue than the alcohol. In other words, the normal spontaneous tendency at this temperature is for the alcohol dehydro-... 

PCBZs demonstrated different behavior from other compounds on the 50% methylphenylsilicone phase. The behavior of PCBZs, indicated by AMIVW, was similar to that of PAHs and that of PMBZs, and PMBZs were similar to allqtl alcohols, as shown in Figure 4.16, where experimental data measured at 200 °C is presented. The alkane MIVW was used as the standard, and the difference of the MIVW for other compounds was related to the optimized energy values for a pair of compounds. The combined energy values of molecular interaction (MIVW) and Avap were related to log k values measured at 200 °C, as shown in Figure 4.16. 

Retention depended on the contact surface area of the molecules. The alkenes with multiple double bonds had less contact surface area and the molecular interaction energy was smaller than that expected from the carbon numbers (surface area). The electrons of double bonds and hydroxyl groups did not affect retention. The relationship between the molecular interaction energy values of allq l alcohols, alkanes and alkenes and their carbon numbers is shown in Figure 6.3. 

The coefficients of the individual groups were elose to 1. The order of the MIFS values was alltyl alcohols > alltyl benzenes > PAHs > alkanes. If the relationship between alkane log k values and their MIFS values is considered as the standard for in silica analysis and the retention is based on a hydro-phobic interaction, the retention of other types of eompounds should follow the relationship of the alkanes. The retention strength was as follows alkanes > PAHs > alkyl benzenes > alkanes, based on the MI energy values. The van der Waals energy values support the strength of hydrophobic retention. If their solvation mechanisms are the same, all eompounds should... 

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