Octafluorocyclobutane

Structural formula
General
Surname	Octafluorocyclobutane ( INN )
other names	Peroctafluorocyclobutane RC318 Cyclooctafluorobutane Freon C318 F318
Molecular formula	C 4 F 8
Brief description	colorless gas with an ethereal odor
External identifiers / databases
CAS number 115-25-3 EC number 204-075-2 ECHA InfoCard 100.003.705 PubChem 8263 Wikidata Q413079
properties
Molar mass	200 g mol −1
Physical state	gaseous
density	6.9 kg m −3 1.639 g · cm −3 of the liquid phase at the boiling point
Melting point	−41 ° C
boiling point	−6.4 ° C
Vapor pressure	269 ​​k Pa (20 ° C)
solubility	very bad in water (140 mg l −1 )
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 280 P: 403
Global warming potential	10592 (based on 100 years)
Thermodynamic properties
ΔH f 0	−1542.6 kJ / mol
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Octafluorocyclobutane is a chemical compound from the group of organic fluorine compounds .

Manufacturing

By full fluorination of cyclobutane with elemental fluorine via radical substitution (for more details see trichloromethane ) the perfluoro compound can be produced:

${\displaystyle \mathrm {C_{4}H_{8}+8\ F_{2}\longrightarrow \ C_{4}F_{8}+8\ HF} }$

properties

Octafluorocyclobutane is a colorless, non-flammable gas with an ethereal odor, which is slightly soluble in water. Industrially, it is supplied in the form of pressurized gas cylinders in which it is in liquefied form. When the liquid flows out or when large amounts of gas escape, cold mists form and spread across the floor. At high concentrations there is a risk of suffocation. Its critical temperature is 115.32 ° C, the critical pressure is 27.8 bar, the critical density is 0.62 kg / l, the triple point temperature is −40.2 ° C and the triple point pressure is 0.191 bar .

use

Octafluorocyclobutane is used in semiconductor technology as an etching and passivation gas (see reactive ion deep etching ). Octafluorocyclobutane is also used as an insulating gas in high-voltage technology because of its high dielectric strength, which is approx. 25% higher at normal pressure than the sulfur hexafluoride (SF ₆ ) used in gas-insulated switchgear .

Ecological aspects

Octafluorocyclobutane is a strong and extremely long-lived greenhouse gas with an atmospheric residence time of 1400 to 3200 years. In 2019 it became known that the actual emissions of some countries are significantly higher than those reported under the Paris climate protection agreement . In addition to India and Russia , increased emissions were detected, especially in China . It is believed that the emissions are related to Teflon production .

Individual evidence

1. ↑ ^{a b c d e f} Praxair: Safety data sheet Octafluorcyclobutane .
2. ↑ ^{a b c d} Entry for CAS no. 115-25-3 in the GESTIS substance database of the IFA , accessed on May 29, 2011(JavaScript required) .
3. ↑ G. Myhre, D. Shindell et al .: Climate Change 2013: The Physical Science Basis . Working Group I contribution to the IPCC Fifth Assessment Report. Ed .: Intergovernmental Panel on Climate Change . 2013, Chapter 8: Anthropogenic and Natural Radiative Forcing, pp. 24-39; Table 8.SM.16 ( PDF ).
4. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-25.
5. ↑ MS Naidu, V. Kamaraju: High Voltage Engineering . 2nd Edition. McGraw-Hill Professional, 1995, ISBN 978-0-07-136108-8 .
6. ↑ Mühle, J., Trudinger, CM et al .: Perfluorocyclobutane (PFC-318, c-C4F8) in the global atmosphere, Atmospheric Chemistry and Physics, 19, 2019, pp. 10335-10359, https://doi.org /10.5194/acp-19-10335-2019 .