Perfluoro-1,2-dioxolane. A new synthesis and its gas-phase structure
摘要:
Highly pure perfluoro-1,2-dioxolane was prepared in good yields by fluorination of 2,2-difluoropropanedioyl difluoride with elemental fluorine in the presence of CsF. A gas-phase electron diffraction study results for the five-membered ring in a half-chair conformation possessing C2 symmetry and the following geometric parameters (r(a) distances and angle(alpha) angles, error limits are 3sigma values and refer to the last digit): O-O = 144.3(11) pm, O-C = 137.7(15) pm, C-C = 153.1(5) pm, (C-F)mean = 131.8(4) pm, CCC = 98.1(13)-degrees, CCO = 107.3(12)-degrees, COO = 102.9(9)-degrees, FCF = 109.8(9)-degrees and the torsional angle around the O-O bond tau(CO-OC) = 48(2)-degrees. Ab initio calculations (HF/4-21G and HF/4-21G*) confirm that this half-chair conformation is the only stable structure along the pseudorotational path and they reproduce the geometric parameters reasonably well.
A new efficient and convenient synthetic process of perfluorinated vinylethers containing an ester group was developed by pyrolysis in the presence of α-trifluoromethyl moiety without loss of –COF functional group followed by alcoholysis in high yield.
The first chamber cleaning gas and the first silicon-containing film-etching gas of the present invention comprise at least one compound selected from the group consisting of FCOF, CF
3
OCOF and CF
3
OCF
2
OCOF, and O
2
in the specific amount, and optionally other gases. The second chamber cleaning gas and the second silicon-containing film-etching gas comprise CF
3
COF, C
3
F
7
COF or CF
2
(COF)
2
and O
2
in specific amounts, and optionally may comprise other gases.
The chamber cleaning gases and silicon-containing film etching gases of the present invention have a low global warming potential and hardly generate substances in the exhaust gases such as CF
4
, etc, which are harmful to the environment and have been perceived as contributing to global warming. Therefore, the gases are friendly to the global environment, and have easy handling and excellent exhaust gas treating properties. Further, the chamber cleaning gases of the invention have excellent cleaning rate.
The first chamber cleaning gas and the first silicon-containing film-etching gas of the present invention comprise at least one compound selected from the group consisting of FCOF, CF3OCOF and CF3OCF2OCOF, and O2 in the specific amount, and optionally other gases. The second chamber cleaning gas and the second silicon-containing film-etching gas comprise CF3COF, C3F7COF or CF2(COF)2 and O2 in specific amounts, and optionally may comprise other gases. The chamber cleaning gases and silicon-containing film etching gases of the present invention have a low global warming potential and hardly generate substances in the exhaust gases such as CF4, etc, which are harmful to the environment and have been perceived as contributing to global warming. Therefore, the gases are friendly to the global environment, and have easy handling and excellent exhaust gas treating properties. Further, the chamber cleaning gases of the invention have excellent cleaning rate.