ISSN:
0947-3440
Keywords:
Anomeric effect
;
Enthalpies of formation
;
Geminal substituents, energetic interaction of
;
Increments, thermochemical, of orthoesters
;
Group increments, interpretation of
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
New enthalpies of formation ΔHf^(g) are provided for the series of orthoesters 2a-2f, 3 and 4 from their enthalpies of combustion ΔHc^ and their enthalpies of vaporization ΔHvap^ or enthalpies of sublimation ΔHsub^. From these data and from literature data the following new thermochemical increments were calculated [kJ · mol-1]: CH[O3] - 106.4, C[O3, C] -103.7, and C[O3, Ph] -124.5. In addition the increment C[O4] - 167.1 was calculated from literature data for ΔHf^(g) of the orthocarbonates 9a and 9b. The anomeric stabilization derived from these results and from previous results for acetals and ketals are reported in Table 3. - A new concept of additive structural increments for the quantitative analysis of the group increments of hydrocarbons, ethers, acetals, and ketals is proposed. It is shown that the increments for CH3, CH2, CH, and C groups with their different neighboring atoms (see Table 4) are determined by the number of hydrogen atoms in the group and by the number of pairwise geminal interactions between all atoms attached to the central carbon atom. - Using this procedure for orthoesters and orthocarbonates, deviations from additivity for the geminal interaction between oxygen atoms, i.e. the anomeric effect, are observed.
Additional Material:
10 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.1995199512291
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