An official website of the United States government
ABSTRACT 2‐chloro‐3,3,3‐trifluoropropene, CF3C(Cl)═CH2(HCFO‐1233xf), is a volatile hydrochlorofluoroolefin, commonly used in industrial synthesis of other halogenated olefins. Kinetics and reaction mechanisms for the reactions of OH radicals, Cl atoms, and O3with CF3C(Cl)═CH2were investigated using FTIR/smog chamber studies in 700 Torr of air/N2diluent at 295 ± 2 K. The rate constantsk(Cl + CF3C(Cl)═CH2) = (8.3 ± 1.1) × 10−11,k(OH + CF3C(Cl)═CH2) = (3.4 ± 0.8) × 10−12andk(O3+ CF3C(Cl)═CH2) = (2.5 ± 0.1) × 10−21cm3molecule−1s−1, were measured. An atmospheric lifetime of 3.3 days for CF3C(Cl)═CH2was determined, dominated by reaction with OH radicals. The reaction of OH radicals and Cl atoms with CF3C(Cl)═CH2proceeds by addition to the double bond, and primary and secondary products of the reactions were quantified. Approximately 90% of Cl atoms undergo addition to the terminal carbon. We were unable to establish any preference of reaction site of the OH addition. Reaction of O3with CF3C(Cl)═CH2leads to the formation of Criegee intermediates that decompose yielding CF3C(O)Cl and HC(O)H as major products. An upper limit of < 0.3% for the yield CF3Cl was estimated. The integrated IR absorption cross‐section for CF3C(Cl)═CH2is (1.22 ± 0.06) × 10−16 cm molecule−1(600–1800 cm−1). The effective radiative efficiency was determined as 0.007 W m−2ppb−1leading to a Global Warming Potential (GWP) for the 100‐year time horizon of 0.031. The environmental impact of release of CF3C(Cl)═CH2to the atmosphere is discussed.
more »
« less
This content will become publicly available on March 19, 2027
Balancing transmetallation and CF 2 α-elimination barriers in organobismuth-catalyzed olefin difluorocarbenation
Organobismuth-catalyzed 1,1-difluorocyclopropanation is an efficient method due to the ability to release CF2in a controlled manner. Transmetallation step is more challenging to address with catalyst tuning than CF2release.
more »
« less
- Award ID(s):
- 2046288
- PAR ID:
- 10678440
- Publisher / Repository:
- Royal Society of Chemistry
- Date Published:
- Journal Name:
- Inorganic Chemistry Frontiers
- ISSN:
- 2052-1553
- Subject(s) / Keyword(s):
- organobismuth, bismuth, difluorocarbene, 1,1-difluorocyclopropane, difluorocyclopropanation, main-group catalysis, hypervalent
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Incorporation of CF2X groups beyond CF3into arene scaffolds is underdeveloped despite these groups’ utility as halogen‐bond donors and as precursors to bioisosteres. Herein, we report the synthesis, characterization, and comparative photochemistry of a suite of [Ag(II)(bpy)2O2CCF2X]+and Ag(II)(bpy)(O2CCF2X)2(bpy = 2,2´‐bipyridine, X = F, CF3, Cl, Br, H, CH3) carboxylate complexes. We find a dramatic effect of the X substituent on the efficiency of generating CF2X radicals by ligand‐to‐metal charge transfer (LMCT), with Ag(II) photoreduction rates varying by over an order of magnitude and quantum yields spanning over 20%. We provide insight into how electronic and structural perturbations of the Ag(II)–O2CCF2X core are manifested in the LMCT quantum efficiency. With this information in hand, Ag(II)‐mediated electrophotocatalytic CF2X functionalization is carried out on a range of (hetero)arenes. This work expands the nascent field of Ag(II)‐based photocatalysis by allowing for (hetero)aryl–CF2X functionalization directly from unactivated fluoroalkyl carboxylate precursors.more » « less
-
Abstract Understanding the electronic structures of high‐valent metal complexes aids the advancement of metal‐catalyzed cross coupling methodologies. A prototypical complex with formally high valency is [Cu(CF3)4]−(1), which has a formal Cu(III) oxidation state but whose physical analysis has led some to a Cu(I) assignment in an inverted ligand field model. Recent examinations of1by X‐ray spectroscopies have led previous authors to contradictory conclusions, motivating the re‐examination of its X‐ray absorption profile here by a complementary method, resonant diffraction anomalous fine structure (DAFS). From analysis of DAFS measurements for a series of seven mononuclear Cu complexes including1, here it is shown that there is a systematic trifluoromethyl effect on X‐ray absorption that blue shifts the resonant Cu K‐edge energy by 2–3 eV per CF3, completely accounting for observed changes in DAFS profiles between formally Cu(III) complexes like1and formally Cu(I) complexes like (Ph3P)3CuCF3(3). Thus, in agreement with the inverted ligand field model, the data presented herein imply that1is best described as containing a Cu(I) ion with dncount approaching 10.more » « less
-
Abstract We report copper(II) and copper(III) trifluoromethyl complexes supported by a pyridinedicarboxamide ligand (L) as a platform for investigating the role of electron transfer in C(sp2)−H trifluoromethylation. While the copper(II) trifluoromethyl complex is unreactive towards (hetero)arenes, the formal copper(III) trifluoromethyl complex performs C(sp2)−H trifluoromethylation of a wide range of (hetero)arenes. Mechanistic studies using the copper(III) trifluoromethyl complex suggest that the mechanism of arene trifluoromethylation is substrate‐dependent. When the thermodynamic driving force for electron transfer is high, the reaction proceeds through a previously unidentified single electron transfer (SET) mechanism, where an initial electron transfer occurs between the substrate and oxidant prior to CF3group transfer. Otherwise, a CF3radical release/electrophilic aromatic substitution (SEAr) mechanism is followed. These studies provide valuable insights into the role of strong oxidants and potential mechanistic dichotomy in Cu‐mediated C(sp2)−H trifluoromethylation.more » « less
