𝔖 Bobbio Scriptorium
✦   LIBER   ✦

Ab initio molecular orbital calculations for 3,6-dihydro-1,2-dithiin and 3,6-dihydro-1,2-dioxin

✍ Scribed by Henry N. Po; Fillmore Freeman; Choonsun Lee; Warren J. Hehre

Publisher
John Wiley and Sons
Year
1993
Tongue
English
Weight
717 KB
Volume
14
Category
Article
ISSN
0192-8651

No coin nor oath required. For personal study only.

✦ Synopsis

Abstract

Optimized geometries and total energies for the conformers of 3,6‐dihydro‐1,2‐dithiin (2) and 3,6‐dihydro‐1,2‐dioxin (3) were calculated at several ab initio MO levels: RHF/3‐21G(*), RHF/6‐31G*, MP2/6‐31G*, and MP2/6‐31G*/ /RHF/3‐21G(*). For the dioxin, in addition to the above levels the corresponding nonextended basis sets ab initio methods were also carried out. The dithiin results are compared with those of simple disulfanes, HSSH and (CH~3~)~2~S~2~, whose optimized geometries agree closely with the observed structures, which is the gauche (C~2~ symmetry). For the disulfanes, the gauche geometries from RHF/3‐21G(*) are in good agreement with the observed structure while the RHF/3‐21G results best fit the dioxin. Pertinent structural data at the RHF/3‐21G(*) for the half‐chair (C~2~) dithiin are: bond lengths, SS, CS, CC, and CC, 2.050, 1.817, 1.515, and 1.317 Å, respectively; bond angles, CSS, CCS, and CCS, 98.0, 114.2, and 127.8°, respectively; CSSC dihedral angle of 63.2°; and twist angle of 36.5°. The total energy for half‐chair dithiin at MP2/6‐31G*//RHF/3‐21G(*) is less than the planar (C~2__v__~) and the half‐boat (C~s~) structures by 69.67 and 29.05 kJ/mol, respectively. The calculated structural data (vs. observed) at RHF/3‐21G for the half‐chair dioxin are: bond lengths, OO, CO, CC, and CC, 1.464 (1.463), 1.454, 1.509, and 1.313 Å (1.338 Å), respectively; bond angles, COO, CCO, and CCO, 105.0, 109.8 (110.3), and 120.7° (119.9°), respectively; COOC dihedral angle of 79.7° (80 ± 2°); and twist angle of 39.0 (38.3°). The total energy for half‐chair dioxin at MP2/6‐31G//RHF/3‐21G is less than the planar and the half‐boat structures by 70.35 and 42.85 kJ/mol, respectively. The total energies calculated at the extended basis sets (*) ab initio levels for the C~2~ symmetry dioxin are much lower than those of the nonextended basis sets. © John Wiley & Sons, Inc.

📜 SIMILAR VOLUMES

Ab initio molecular orbital study of ene
Ab initio molecular orbital study of energies and conformers of 3,4-dihydro-1,2-dithiin, 3,6-dihydro-1,2-dithiin, 4H-1,3-dithiin, and 2,3-dihydro-1,4-dithiin
✍ Freeman, Fillmore; Lee, Choonsun; Po, Henry N.; Hehre, Warren J. 📂 Article 📅 1998 🏛 John Wiley and Sons 🌐 English ⚖ 228 KB 👁 2 views

Optimized geometries and energies for 3,4-dihydro-1,2-dithiin Ž . Ž . Ž . Ž . 1 , 3,6-dihydro-1,2-dithiin 2 , 4H-1,3-dithiin 3 , and 2,3-dihydro-1,4-dithiin 4 were calculated using ab initio 6-31G U and MP2r6-31G U rr6-31G U methods. At the MP2r6-31G U rr6-31G U level, the half-chair conformer of 4

tert-Butyl N-(3,6-dihydro-1,2-dioxin-4-y
tert-Butyl N-(3,6-dihydro-1,2-dioxin-4-ylmethyl)carbamate
✍ Sejer Pedersen, Daniel ;Taylor, Dennis K. ;Tiekink, Edward R. T. 📂 Article 📅 2007 🏛 International Union of Crystallography 🌐 English ⚖ 982 KB

The six-membered ring in the title compound, C~10~H~17~NO~4~, has a half-chair conformation and lies to one side of the central chromophore. Molecules are connected into a supramolecular chain __via__ N—H...O hydrogen-bonding interactions and these are consolidated into a three-dimensional structure