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Quantum semiempirical study on the reactivity of silylated diamines in the synthesis of aromatic polyamides

✍ Scribed by Angel E. Lozano; Javier de Abajo; José G. De la Campa

Publisher
John Wiley and Sons
Year
1998
Tongue
English
Weight
638 KB
Volume
7
Category
Article
ISSN
1022-1344

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✦ Synopsis

The reasons for the reactivity increase toward acyl chlorides caused in aromatic amines by silylation are studied by quantum semiempirical and ub initio methods. Silylated amino groups adopt an sp2 planar geometry, in contrast to that observed in the unsilylated series, where a partially pyramidal structure intermediate between sp3 and sp2 geometry was obtained. Silylation also causes a strong increase of electronic density on the amine nitrogen and an increase of the Highest Occupied Molecular Orbital (HOMO) energy, both effects favoring the higher reactivity of these silylated amines. In addition to that, silylation produces a decrease of the activation energy in the reaction with an acyl chloride, relative to the unsilylated amines, thus increasing reaction rate.

Computational methods and calculations

Semiempirical calculations were made by using the original parameters of the program AM1, based on the restricted Hartree-Fock (RHF) method, included in MOPAC version 6.0"). Additionally, the results of AM 1 on some selected molecules were checked with the pro-

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