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AM1 calculations of parts of the enthalpy surfaces for additions of active methylene nitriles to α β-unsaturated nitriles

✍ Scribed by S. El-Taher; M. H. Elnagdi

Publisher
John Wiley and Sons
Year
1997
Tongue
English
Weight
219 KB
Volume
8
Category
Article
ISSN
1042-7163

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✦ Synopsis

The nucleophilic additions of active methylene nitriles (MNs), R 1 R 2 CH ‫מ‬ , where R 1 ‫ס‬CN and R 2 ‫ס‬CN, and CSNH 2 , to acetaldehyde and to the resultant ␣,b-unsaturated nitriles have been studied theoretically by the AM1 semiempirical MO method. The additions of MNs anions to acetaldehyde are found to be endothermic with late productlike transition states (TSs) on the reaction coordinate. Their additions to ␣,b-unsaturated nitriles may conceivably proceed via two pathways: addition to the C‫ס‬C double bond and addition to the CϵN triple bond. It has been found that the nucleophilic attack at the ␣,b-unsaturated linkage is exothermic, while that at the nitrile group is endothermic and has a relatively high enthalpy barrier. Both additions have late productlike transition states. The reactivity of the nucleophilic attack has been discussed in the light of the frontier molecular orbital theory and in terms of the HOMO-LUMO two-electron interaction. The calculations have been compared with experimental results.

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