Location of para-Xylene in Yb-Faujasite (Zeolite Y) by Neutron Diffraction
✍ Scribed by Dipl-Chem. Mirjam Czjzek; Dr. Thomas Vogt; Prof. Dr. Hartmut Fuess
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 381 KB
- Volume
- 28
- Category
- Article
- ISSN
- 0044-8249
No coin nor oath required. For personal study only.
✦ Synopsis
tion of the =SF, group by 90" relative to the =C(CF,), group is 91 kJ mol-' higher; this provides a qualitative idea of the amount of C-S double bonding, which was calculated to be approximately 122 kJ mol-' for alkylidene sulfur tetrafluorides.['I
The calculation could also be performed for the isomer pair F,C = SF,/F,C -SF using once again the larger basis set. Surprisingly, a new structure 8 was predicted to be more stable. This molecule is fully planar and the SF, group is nearly linear. The C-S R bond lies outside of the molecular plane to the extent of 98 YO. This atomic arrangement corresponds to a minimum since all eigenvalues of the second-derivative matrix are positive. This molecule, which cannot be easily described according to conventional models, presents a challenge for the experimentalist. A possible model is of-F F fered by 8. It has thus been shown once again that SF, substitution stabilizes unusual bonding patterns. Experimental Procedure 3: 1 (3.8 g, 20 mmol), SF, (2.16 g, 20 mmol), and CsF (9 g. 59 mmol) were stirred in a stainless-steel autoclave at 70°C for 3 d. The product was isolated in a -78 "C trap by fractional condensation under dynamic vacuum. Colorless liquid (b.p. 6 4 T , extrapolated from the vapor pressure curve), overall yield of the isomeric mixture 84%, isomer ratio 8:l (according to I9F NMR). Raman (liq.): strong bands at C = 989.0 (s,p), 734.5 (s,p), 717.0 (vs.~), 678.0 ( v s , ~) , 466.5(s,p),453.5(vs,p),406.0(s,p), 324.0(s,dp),314.0(s,dp),288.0(vs,p).231.0 (s,dp) cm-'. IR (gas): strong bands at V = 1274 (vs), 1228 (vs), 1180 (vs), 901 (vs), 887 (vs), 854 (vs), 834 (s) cm-I .