𝔖 Bobbio Scriptorium
✦   LIBER   ✦

Localized molecular orbitals and chemical binding in five-membered heterocycles. II

✍ Scribed by Rifaat Hilal

Publisher
John Wiley and Sons
Year
1980
Tongue
English
Weight
696 KB
Volume
1
Category
Article
ISSN
0192-8651

No coin nor oath required. For personal study only.

✦ Synopsis

Abstract

The localized molecular orbitals (LMOs) of thiophene, furan, and pyrrole are derived from ab initio 4‐31G wavefunctions using Boys' criteria for localization. From the transferability point of view, these LMOs are classified as (i) completely different and nontransferable LMOs (these are the lone‐pair orbitals on O and N on one hand and those on S on the other hand), (ii) chemically similar lone pairs and inner shells on O and N (of furan and pyrrole, respectively), and (iii) chemically equivalent CC, CC, and CH LMOs in the three heterocycles. The sp^3^ hybridization of the L core of sulfur, its appreciable polarization, and considerable involvement in bonding in the CS bond region have been discussed. The present investigation indicates the limitation of the application of semiempirical MO methods to molecules that contain second‐row atoms due to both the appreciable core—valence and π‐σ interactions involving such atoms. Qualitative investigation of aromaticity and reactivity of the studied heterocycles agrees satisfactorily with experimental observations and shows that conclusions drawn based solely on static factor considerations (charge distribution in the noninteracting molecules) might very well be misleading and such factors determine the ease rather than the final orientation of the substituent.

📜 SIMILAR VOLUMES

Molecular charge distribution and chemic
Molecular charge distribution and chemical binding in five-membered heterocycles. I
✍ Rifaat Hilal 📂 Article 📅 1980 🏛 John Wiley and Sons 🌐 English ⚖ 807 KB

## Abstract Electron density maps for the heterocycles thiophene, furan, and pyrrole are determined from __ab initio__ 4‐31G wavefunctions. The charge distributions in these molecules are analyzed in terms of the total molecular density and difference density maps and their profiles. The atomiclike

Difference between 2JC2H3 and 2JC3H2 spi
Difference between 2JC2H3 and 2JC3H2 spin–spin couplings in heterocyclic five- and six-membered rings as a probe for studying σ-ring currents: a quantum chemical analysis
✍ Rubén H. Contreras; Francisco P. dos Santos; Lucas C. Ducati; Cláudio F. Tormena 📂 Article 📅 2010 🏛 John Wiley and Sons 🌐 English ⚖ 214 KB

Adequate analyses of canonical molecular orbitals (CMOs) can provide rather detailed information on the importance of different σ-Fermi contact (FC) coupling pathways (FC term transmitted through the σ-skeleton). Knowledge of the spatial distribution of CMOs is obtained by expanding them in terms of

Aliphatic, alicyclic, and saturated hete
Aliphatic, alicyclic, and saturated heterocyclic chemistry, specialist periodical reports, volume 1 (in three parts). Part I: Aliphatic chemistry, vii + 213 pp. Part II: Three- and four-membered rings (carbocyclic and saturated heterocyclic). ix + 517 pp. Part III: Five- and six-membered rings; medium sized rings; bridged and caged systems (carbocyclic and saturated heterocyclic). xi + 567 pp. senior reporter, W. PARKER. The Chemical Society, Burlington House, London, WIV OBN, England, 1973. 14.5 × 22 cm. Price £20.00 (all three parts)
✍ Y. F. Shealy 📂 Article 📅 1974 🏛 John Wiley and Sons 🌐 English ⚖ 223 KB