75-00-3 Usage
Uses
Used in Chemical Synthesis:
Chloroethane is used as a reactant in organic synthesis for the production of various chemicals and intermediates. Its reactivity makes it a valuable component in the synthesis of pharmaceuticals, agrochemicals, and other specialty chemicals.
Used in the Refrigeration Industry:
Chloroethane is used as a refrigerant in cooling systems due to its thermodynamic properties, which allow for efficient heat transfer and cooling.
Used as a Solvent:
Chloroethane is used as a solvent in various industrial processes, including the production of synthetic gums and thickeners in the lacquer and plastics industries. Its solvent properties make it suitable for dissolving a wide range of substances.
Used in the Manufacture of Tetraethyl Lead:
Chloroethane serves as a starting point in the production of tetraethyl lead, an antiknock agent used in gasoline. This application highlights its importance in the petrochemical industry.
Used in the Friedel-Crafts Alkylation:
Chloroethane is used in the Friedel-Crafts alkylation of benzene and other aromatic compounds, a reaction that is crucial for the synthesis of various organic compounds.
Used as a Heat-Transfer Medium:
Chloroethane is utilized as a heat-transfer medium in industrial processes due to its thermal properties, which allow for efficient heat transfer and temperature control.
Used as an Aerosol Propellant:
Chloroethane is used as an aerosol propellant in the production of spray products, such as paints, coatings, and personal care products.
Used as a Topical Anesthetic:
Chloroethane is used as a topical anesthetic in medical applications, providing localized pain relief and numbing effects on the skin and mucous membranes.
Production
The dominant process for production of ethyl chloride in the USA involves the addition of anhydrous hydrogen chloride to ethylene in the presence of an aluminium chloride catalyst. The hydrochlorination is a liquidphase reaction, carried out at about 40°C. Reacted products are fed into a flash evaporator column, where ethyl chloride is separated from less volatile compounds and then purified by fractionation. Hydrochlorination of ethanol has not been used for US ethyl chloride production since 1980, and chlorination of ethane (catalytically, electrolytically, thermallyor photochemically) has not been used at any production facility in the USA since 1974. Ethyl chloride is also obtained as a by-product from the production of vinyl chloride[1] or chlorofluorocarbon, although this method accounts for only a small amount.
Source and exposure
Sources of possible ethyl chloride exposure include the inhalation of contaminated air and ingestion of contaminated drinking water at very low levels. The general population can be exposed to ethyl chloride by skin contact with consumer products that contain ethyl chloride such as solvents and refrigerants. Occupational exposure by inhalation or dermal contact with ethyl chloride can occur in industries such as medical and health services; automotive dealers and service stations; wholesale trade, electric, gas, and sanitary services; machinery (except electrical) and special trade contractors; fabricated metal productions; printing and publishing; painting; rubber and plastic products; and food.[1]?Although chemists use tests such as gas chromatography to measure ethyl chloride in blood, milk, or urine, no commonly used medical tests are available to determine whether or not a person has been exposed to ethyl chloride.[1]
Toxicity
Acute Effects
Acute inhalation exposure to high levels of ethyl chloride in humans has resulted in temporary feelings of drunkenness, dizziness, lack of muscle coordination and unconsciousness. Accidental death has resulted from its former medical use as an anesthetic during major surgery.[1,2] Tests involving acute exposure of animals in rats and mice have shown ethyl chloride to have low toxicity from inhalation exposure.[3]
Chronic Effects
Neurological symptoms including ataxia, tremors, speech difficulties, slowed reflexes, involuntary eye movement, and hallucinations, and liver effects were reported in individuals who purposely inhaled very high concentrations of ethyl chloride for a few months.[4]
Some animal studies indicate effects on the lungs, liver, kidneys, and heart due to ethyl chloride exposure via inhalation.[1] The Reference Concentration (RFC) for ethyl chloride is 10 milligrams per cubic meter (mg/m3) based on delayed fetal ossification in mice. The RFC is an estimate (with uncertainty spanning perhaps an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups), which is likely to be without appreciable risk of deleterious noncancer effects during a lifetime. It is not a direct esimator of risk but rather a reference point to gauge the potential effects. At exposures increasingly greater than the RFC, the potential for adverse health effects increases. Lifetime exposure above the RFC does not imply that an adverse health effect would necessarily occur.[4]
EPA has medium confidence in the study on which the RFC is based because, although the study is well conducted, it does not establish a firm concentration-response relationship with an adverse effect and was not performed at levels eliciting maternal toxicity; medium confidence in the database due to the lack of a multigenerational reproductive study and a developmental study in a second species; and, consequently, medium confidence in the RFC.[4]?EPA has not established a Reference Dose (RfD) for ethyl chloride.[4] Reproductive/Developmental Effects
No studies were located regarding reproductive or developmental effects following ethyl chloride inhalation exposure in humans.
Several animal studies found no reproductive effects caused by ethyl chloride exposure. An animal study reported a decrease in uterine weights, while another study reported minimal evidence of fetotoxicity (increase in centers of unossified bones of the skull) from inhalation exposure to ethyl chloride.[1]
Cancer Risk
There are no human cancer data available for ethyl chloride. A 2-year bioassay performed by the NTP indicated that inhaled ethyl chloride is carcinogenic in female mice and may be carcinogenic in rats. Female mice experienced a significant increase in the incidence of uterine tumors and hepatocellular tumors, but the data on male mice were considered inadequate because of a low survival rate. Benign and malignant epithelial neoplasms of the skin, and three uncommon malignant astorcyomas of the brain, were reported in male and female rats, respectively.[5] EPA has not classified ethyl chloride for carcinogenicity.[4]
References
Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Ethyl chloride (Update).Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA. 1998.
U.S. Department of Health and Human Services. Hazardous Substances Data Bank (HSDB, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.
U.S. Department of Health and Human Services. Registry of Toxic Effects of Chemical Substances (RTECS, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.
U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on Ethyl Chloride. National Center for Environmental Assessment, Office of Research and Development, Washington, DC. 1999.
National Toxicology Program. Toxicology and Carcinogenesis Studies of Ethyl chloride (Ethyl Chloride) (CAS No. 75-00-3) in F344/N Rats and B6C3F1 Mice (Inhalation Studies). TR No. 346. U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health, Bethesda, MD. 1989.
The Merck Index. An Encyclopedia of Chemicals, Drugs, and Biologicals. 11th ed. Ed. S. Budavari. Merck and Co. Inc., Rahway, NJ. 1989.
J.E. Amoore and E. Hautala. Odor as an aid to chemical safety: Odor thresholds compared with threshold limit values and volatilities for 214 industrial chemicals in air and water dilution. Journal of Applied Toxicology, 3(6):272-290. 1983.
Indications
Chlorethane (ethyl chloride) is a highly flammable liquid that acts as a topical vapocoolant
to control pain associated with minor surgical procedures.When applied as
a spray, the product produces freezing of superficial tissues to ?20?C, which results
in insensitivity of peripheral nerve endings and local anesthesia that is maintained
up to 1 minute. Other coolant sprays can be used with the same effect.
Production Methods
Ethyl Chloride can be synthesized by treatment of ethyl alcohol with HCl, cleavage of diethylether with HCl in the presence of a catalyst (ZnCl2), chlorination of ethane or hydrochlorination of ethylene. The latter is the choice of industry. The reaction is carried out at 125 °F and 125 psi in the presence of AlCl3, which is dissolved in ethyl chloride.
Air & Water Reactions
Highly flammable. Insoluble in water.
Reactivity Profile
CHLOROETHANE is heat sensitive. CHLOROETHANE will hydrolyze in the presence of alkalis and water. CHLOROETHANE reacts with water or steam to produce toxic and corrosive fumes. CHLOROETHANE can also react vigorously with oxidizing materials. The vapor forms highly flammable mixtures with air. A mixture of CHLOROETHANE with potassium is shock-sensitive. Contact with chemically active metals such as Na, K, Ca, powdered Al, Zn and Mg may result in violent reactions.
Hazard
Highly flammable, severe fire and explosion risk; flammable limits in air 3.8–15.4%. Irritant
to eyes. Questionable carcinogen.
Health Hazard
Vapor causes drunkenness, anesthesia, possible lung injury. Liquid may cause frostbite on eyes and skin.
Health Hazard
Exposure to high levels of ethyl chloride cancause stupor, eye irritation, incoordination,abdominal cramps, anesthetic effects, cardiacarrest, and unconsciousness. No toxic effectswere noted at a concentration of 10,000 ppm.A 45-minute exposure to a 4% concentrationof ethyl chloride in air was lethal to guineapigs. A brief exposure for 5 to 10 minutes toa concentration of 10% of the gas was notfatal to the test animals but caused kidneyand liver damage. In humans narcotic effectsmay occur after a few inhalations of 5–10%concentrations of the gas. Irritant effectson the eyes, skin, and respiratory tract aremild. Skin contact with the liquid can causefrostbite due to cooling by rapid evaporation.LC50 value, inhalation (rats): 60,000 ppm/2 hr.
Safety Profile
Suspected carcinogen
with experimental carcinogenic and
neoplastigenic data. Mildly toxic by
inhalation. An irritant to sh, eyes, and mucous membranes. The liquid is harmful
to the eyes and can cause some irritation. In
the case of guinea pigs, the symptoms
attending exposure are similar to those
caused by methyl chloride, except that the
signs of lung irritation are not as
pronounced. It gives some warning of its
presence because it is irritating, but it is
possible to tolerate exposure to it until one
becomes unconscious. It is the least toxic
of all the chlorinated hydrocarbons. It can
cause narcosis, although the effects are
usually transient.
A very dangerous fire hazard when
exposed to heat or flame; can react
vigorously with oxidizing materials. Severe
explosion hazard when exposed to flame.
Reacts with water or steam to produce toxic
and corrosive fumes. Incompatible with
potassium. To fight fire, use carbon dioxide.
When heated to decomposition it emits
toxic fumes of phosgene and Cl-. See also
CHLORINATED HYDROCARBONS,
ALIPHATIC.
Potential Exposure
Ethyl chloride is used as an ethylating
agent in the manufacture of tetraethyl lead, dyes, drugs,
and ethyl cellulose; as a pharmaceutical, solvent; alkylating
agent; as a refrigerant and as a local anesthetic (freezing).
Carcinogenicity
The EPA has not made a
carcinogenicity assessment as yet. However, the State of
California reviewed the carcinogenicity information.
CalEPA, using the NTP study, developed a cancer
potency estimate of 4.7E-3 per mg/kg/day and defined a No
Significance Risk Level (NSRL) of 1 50 μg/day.
Increased cancer of the uterus of female mice has been
produced by exposure to 15,000 ppm, but lower concentrations
have not been studied. Rats and mice were exposed to 0
or 15,000 ppm of ethyl chloride in an NTP 2-year study with
mixed results. Results in male rats were considered
equivocal based on a combined total of five skin tumors
versus none in the control male rats. Likewise, female rats’
results were considered equivocal because three astrocytomas
were found versus none in the female control rats. The
male mouse group had such poor survival that it was deemed
an inadequate study although combined alveolar/bronchiolar
adenomas and carcinomas were reported (10/48 versus 5/50
in the control male rats). Female mice exposed to 15,000 ppm
had clear evidence of an effect, for 43/50 mice had endometrial
uterine carcinomas versus 0/49 in the female control
mice. In addition, there was a suggestion of an increase in
combined hepatocellular adenomas and carcinomas in the
female mice (8/48 exposed versus 3/49 control). There is
clear evidence for carcinogenicity in female B6C3F1 mice
and equivocal evidence in male and female F344/N rats (high
incidence of uterine carcinomas.)
Environmental fate
Photolytic. The rate constant for the reaction of chloroethane and OH radicals in the atmosphere
at 300 K is 2.3 x 10-11 cm3/molecule?sec (Hendry and Kenley, 1979). At 296 K, a photooxidation
rate constant of 3.9 x 10-13 cm3/molecule?sec was reported (Howard and Evenson, 1976). The
estimated tropospheric lifetime is 14.6 d (Nimitz and Skaggs, 1992).
Chemical/Physical. Under laboratory conditions, chloroethane hydrolyzed to ethanol (Smith and
Dragun, 1984). An estimated hydrolysis half-life in water at 25 °C and pH 7 is 38 d, with ethanol
and HCl being the expected end-products (Mabey and Mill, 1978). Based on a measured
hydrolysis rate constant of 5.1 x 10-7 at 25 °C and pH 7, the half-life is 2.6 yr (Jeffers and Wolfe,
1996).
In air, formyl chloride is the initial photooxidation product (U.S. EPA, 1985). In the presence of
water, formyl chloride hydrolyzes to HCl and carbon monoxide (Morrison and Boyd, 1971).
Burns with a smoky, greenish flame releasing hydrogen chloride (Windholz et al., 1983).
In the laboratory, the evaporation half-life of chloroethane (1 mg/L) from water at 25 °C using a
shallow-pitch propeller stirrer at 200 rpm at an average depth of 6.5 cm was 23.1 min (Dilling,
1977).
At influent concentrations of 1.0, 0.1, and 0.01 mg/L, the GAC adsorption capacities at pH 5.3
were 0.59, 0.07, and 0.007 mg/g, respectively (Dobbs and Cohen, 1980).
Solubility in water
Soluble in ethanol, ether (U.S. EPA, 1985); miscible with chlorinated hydrocarbons such as
chloroform, carbon tetrachloride, and tetrachloroethane.
Shipping
UN1037 Ethyl chloride, Hazard Class: 2.1;
Labels: 2.1-Flammable gas. Cylinders must be transported
in a secure upright position, in a well-ventilated truck.
Protect cylinder and labels from physical damage. The
owner of the compressed gas cylinder is the only entity
allowed by federal law (49CFR) to transport and refill
them. It is a violation of transportation regulations to refill
compressed gas cylinders without the express written permission of the owner.
Purification Methods
Pass ethyl chloride through absorption towers containing, successively, conc H2SO4, NaOH pellets, P2O5 on glass wool, or soda-lime, CaCl2, P2O5. Condensed it into a flask containing CaH2 and fractionally distil it. It has also been purified by illumination in the presence of bromine at 0o using a 1000W lamp, followed by washing, drying and distilling. [Beilstein 1 IV 124.]
Incompatibilities
Flammable gas. Slow reaction with
water; forms hydrogen chloride gas. Contact with moisture
(water, steam) forms hydrochloric acid and/or fumes of
hydrogen chloride. May accumulate static electrical
charges, and may cause ignition of its vapors. May form
explosive mixture with air. Contact with chemically active
metals: aluminum, lithium, magnesium, sodium, potassium,
zinc may cause fire and explosions. Attacks some plastics
and rubber.
Waste Disposal
Return refillable compressed
gas cylinders to supplier. Incineration, preferably after mixing with another combustible fuel. Care must be exercised
to assure complete combustion to prevent the formation of
phosgene. An acid scrubber is necessary to remove the halo
acids produced.
Check Digit Verification of cas no
The CAS Registry Mumber 75-00-3 includes 5 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 2 digits, 7 and 5 respectively; the second part has 2 digits, 0 and 0 respectively.
Calculate Digit Verification of CAS Registry Number 75-00:
(4*7)+(3*5)+(2*0)+(1*0)=43
43 % 10 = 3
So 75-00-3 is a valid CAS Registry Number.
InChI:InChI=1/C2H5Cl/c1-2-3/h2H2,1H3
75-00-3Relevant articles and documents
Kinetics of the Liquid-Phase Hydrochlorination of Ethanol
Makhin,Dmitriev,Zanaveskin
, p. 553 - 556 (2018)
The results of a study on the kinetics of the liquid-phase hydrochlorination of ethanol with hydrogen chloride are presented. The form of the rate equation, the preexponential factor, the activation energy, and the empirical coefficients that characterize the effect of chloride anion hydration on the reaction rate of ethanol hydrochlorination were determined. The rates of hydrochlorination of monohydric alcohols and polyols were compared based on the examples of methanol, ethanol, 1,2-propylene glycol, and glycerol.
Stable C2H5X(1+). (X=Cl, Br) Radical Cations of Structure : Their Energetics and Dissociation Characteristics
Holmes, John L.,Burgers, Peter C.,Terlouw, Johan K.,Schwarz, Helmut,Ciommer, Bernhard,Halim, Herman
, p. 208 - 211 (1983)
A new radical cation having the methyl carbene type structure (1+). has been characterized in the gas phase.It is readily generated by dissociative ionization (1+). -> CO2+(1+)..Its enthalpy of formation has been estimated to be 951 kJ mol-1, close to that of (1+)..The principal fragmentation characteristics (loss of HCl and Cl.) of the ion are discussed.A brief description of the bromo analogue (1+). is also given.
Electrophilic addition reaction of ethene with hydrogen chloride on cold molecular films: Evidence of ethyl cationic intermediate
Lee, Poong-Ryul,Lee, Chang-Woo,Kim, Joon-Ki,Moon, Eui-Seong,Kang, Heon
, p. 938 - 944 (2011)
We studied the initial-stage mechanism of the electrophilic addition reaction of ethene with HCl by examining the interactions between ethene and HCl on water-ice and frozen molecular films at temperatures of 80-140 K. Cs + reactive ion scattering (RIS) and low-energy sputtering (LES) techniques were used to probe the reaction intermediates that were kinetically trapped on the surface, in conjunction with temperature-programmed desorption (TPD) mass spectrometry to monitor the desorbing species. The reaction initially produced the π complex of HCl and ethene at temperatures below about 93 K and an "ethyl cationic species" at temperatures below about 100 K. The ethyl cationic species was formed via direct proton transfer from the HCl molecule to ethene with the assistance of water solvation, rather than via the interaction of hydronium ions and ethene. At high temperatures, this species dissociated into ethene and hydronium and chloride ions. The reaction did not, however, complete the final transition state on the ice surface to produce ethyl chloride. The observation gives evidence that the electrophilic addition reaction of ethene occurs through an ethyl-like intermediate with an ionic character. A cold ice surface can halt a reaction at an intermediate stage. An ethyl cationic intermediate is kinetically trapped on the ice surface in the course of the electrophilic addition reaction of ethene with hydrogen chloride, as revealed by reactive ion scattering and thermal desorption mass spectrometry.
Nitrogen-Doped Carbon-Assisted One-pot Tandem Reaction for Vinyl Chloride Production via Ethylene Oxychlorination
Chen, De,Chen, Qingjun,Fuglerud, Terje,Ma, Guoyan,Ma, Hongfei,Qi, Yanying,Rout, Kumar R.,Wang, Yalan
supporting information, p. 22080 - 22085 (2020/10/02)
A bifunctional catalyst comprising CuCl2/Al2O3 and nitrogen-doped carbon was developed for an efficient one-pot ethylene oxychlorination process to produce vinyl chloride monomer (VCM) up to 76 % yield at 250 °C and under ambient pressure, which is higher than the conventional industrial two-step process (≈50 %) in a single pass. In the second bed, active sites containing N-functional groups on the metal-free N-doped carbon catalyzed both ethylene oxychlorination and ethylene dichloride (EDC) dehydrochlorination under the mild conditions. Benefitting from the bifunctionality of the N-doped carbon, VCM formation was intensified by the surface Cl*-looping of EDC dehydrochlorination and ethylene oxychlorination. Both reactions were enhanced by in situ consumption of surface Cl* by oxychlorination, in which Cl* was generated by EDC dehydrochlorination. This work offers a promising alternative pathway to VCM production via ethylene oxychlorination at mild conditions through a single pass reactor.
Halogen-Dependent Surface Confinement Governs Selective Alkane Functionalization to Olefins
Zichittella, Guido,Scharfe, Matthias,Puértolas, Bego?a,Paunovi?, Vladimir,Hemberger, Patrick,Bodi, Andras,Szentmiklósi, László,López, Núria,Pérez-Ramírez, Javier
supporting information, p. 5877 - 5881 (2019/02/20)
The product distribution in direct alkane functionalization by oxyhalogenation strongly depends on the halogen of choice. We demonstrate that the superior selectivity to olefins over an iron phosphate catalyst in oxychlorination is the consequence of a surface-confined reaction. By contrast, in oxybromination alkane activation follows a gas-phase radical-chain mechanism and yields a mixture of alkyl bromide, cracking, and combustion products. Surface-coverage analysis of the catalyst and identification of gas-phase radicals in operando mode are correlated to the catalytic performance by a multi-technique approach, which combines kinetic studies with advanced characterization techniques such as prompt-gamma activation analysis and photoelectron photoion coincidence spectroscopy. Rationalization of gas-phase and surface contributions by density functional theory reveals that the molecular level effects of chlorine are pivotal in determining the stark selectivity differences. These results provide strategies for unraveling detailed mechanisms within complex reaction networks.
Synthesis and reactivity of platinum vinylcarbene complexes prepared from activation of propargyl alcohols
Ruan, Wenqing,Shi, Chuan,Sung, Herman H.Y.,Williams, Ian D.,Jia, Guochen
, p. 7 - 14 (2018/11/06)
Platinum vinylcarbene complexes are potentially useful for organometallic synthesis and catalysis, but have been rarely studied. This work reports a convenient route to make platinum vinylcarbene complexes. Treatment of [PtCl2(PPh3)]2 with propargyl alcohols HC≡CC(OH)RR’ (RR’ = Ph2, cyclo-C6H10(OH), (iPr)(C≡CTMS) and (H)(Ph)) in the presence of EtOH produced the vinylcarbene complexes trans-PtCl2{ = C(OEt)-CH=CRR’}(PPh3). Under similar condition, [PtCl2(PPh3)]2 reacted with HC≡CC(OH)Me2 to give cis-PtCl2{ = C(OEt)-CH=CMe2}(PPh3). Complex trans-PtCl2{ = C(OEt)-CH=CPh2}(PPh3) readily undergo a metathesis reaction with NaI to give trans-PtI2{ = C(OEt)-CH=CPh2}(PPh3) which can isomerize to cis-PtI2{ = C(OEt)-CH=CPh2}(PPh3). Complex trans-PtCl2{ = C(OEt)-CH=CPh2}(PPh3) reacted with PPh3 to give EtCl and the acyl complex trans-PtCl{C(O)CH=CPh2}(PPh3)2, which can undergo a decarbonylation reaction to give PtCl(CH=CPh2)(PPh3)2.
Selective Photo-Oxygenation of Light Alkanes Using Iodine Oxides and Chloride
Liebov, Nichole S.,Goldberg, Jonathan M.,Boaz, Nicholas C.,Coutard, Nathan,Kalman, Steven E.,Zhuang, Thompson,Groves, John T.,Gunnoe, T. Brent
, p. 5045 - 5054 (2019/10/28)
Partial oxidation of light alkanes to generate alkyl esters has been achieved under photochemical conditions using mixtures of iodine oxides and chloride salts in trifluoroacetic acid (HTFA). The reactions are catalytic in chloride and are successful using compact fluorescent light, but higher yields are obtained using a mercury lamp. In this photo-initiated oxyesterification process, the robust alkyl ester products are resistant to over-oxidation, and under optimized conditions yields for alkyl ester production of ～50 % based on methane, ～60 % based on ethane (with a total functionalized yield of EtX (X=TFA or Cl) of 80 %) and ～30 % based on propane have been demonstrated. The reaction also proceeds in aqueous HTFA and dichloroacetic acid with lower yields. Mechanistic studies indicate that the process likely operates by a chlorine hydrogen atom abstraction pathway wherein alkyl radicals are generated, trapped by iodine, and converted to alkyl trifluoroacetates in situ.
PROCESS AND INTERMEDIATE FOR THE MANUFACTURE OF DIFLUOROACETYL CHLORIDE
-
Page/Page column 14; 15, (2019/03/17)
The present invention concerns a process and intermediates for the manufacture of difluoro acetyl chloride. The invention further concerns a process for the manufacture of an agrochemically or pharmaceutically active compound, which comprises the process and intermediate for the manufacture of difluoro acetyl chloride for the manufacture of difluoro acetyl chloride or its intermediate.
An Activated TiC–SiC Composite for Natural Gas Upgrading via Catalytic Oxyhalogenation
Zichittella, Guido,Puértolas, Bego?a,Siol, Sebastian,Paunovi?, Vladimir,Mitchell, Sharon,Pérez-Ramírez, Javier
, p. 1282 - 1290 (2018/02/09)
Alkane oxyhalogenation has emerged as an attractive catalytic route for selective natural gas functionalization to important commodity chemicals, such as methyl halides or olefins. However, few systems have been shown to be active and selective in these reactions. Here, we identify a novel and highly efficient TiC–SiC composite for methane and ethane oxyhalogenation. Detailed characterization elucidates the kinetics and mechanism of the selective activation under reaction conditions to yield TiO2–TiC–SiC. This catalyst outperforms bulk TiO2, one of the best reported catalysts, reaching up to 85 % selectivity and up to 3 times higher titanium-specific space-time-yield of methyl halides or ethylene. This is attributed to the fact that the active TiO2 phase generated in situ is embedded in the thermally conductive SiC matrix, facilitating heat dissipation thus improving selectivity control.
Mechanism of Hydrocarbon Functionalization by an Iodate/Chloride System: The Role of Ester Protection
Schwartz, Nichole A.,Boaz, Nicholas C.,Kalman, Steven E.,Zhuang, Thompson,Goldberg, Jonathan M.,Fu, Ross,Nielsen, Robert J.,Goddard, William A.,Groves, John T.,Gunnoe, T. Brent
, p. 3138 - 3149 (2018/04/14)
Mixtures of chloride and iodate salts for light alkane oxidation achieve >20% yield of methyl trifluoroacetate (TFA) from methane with >85% selectivity. The mechanism of this C-H oxygenation has been probed by examining adamantane as a model substrate. These recent results lend support to the involvement of free radicals. Comparative studies between radical chlorination and iodate/chloride functionalization of adamantane afford statistically identical 3°:2° selectivities (～5.2:1) and kinetic isotope effects for C-H/C-D functionalization (kH/kD = 1.6(3), 1.52(3)). Alkane functionalization by iodate/chloride in HTFA is proposed to occur through H-atom abstraction by free radical species including Cl? to give alkyl radicals. Iodine, which forms by in situ reduction of iodate, traps alkyl radicals as alkyl iodides that are subsequently converted to alkyl esters in HTFA solvent. Importantly, the alkyl ester products (RTFA) are quite stable to further oxidation under the oxidizing conditions due to the protecting nature of the ester moiety.
