The Chlorine-Sensitized Photo-Oxidation of Tetrachloroethylene in Carbon Tetrachloride Solution

ECKART MATHIAS, EUGENIO SANHUEZA, I. C. HISATSUNE, and JULIAN HEICKLEN. Can. J. Chem. 52,3852 (1974).The chlorine atom initiated oxidation of CzC14 was studied both in the absence and presence of 0 3 at 24 and 32 "C. In the absence of 0 3 , the products are CCl,CCl(O) and CC120, and they are produced in a long-chain process in a ratio of 2.5 at 24 "C and 3.0 at 32 "C. The product producing step involves the decay of C2Cl50 radicals [6alThe ratio k6,/ksb is 5.0 at 24 "C and 6.0 at 32 "C since CCl, reacts with O2 to produce another CC1,O molecule. In the presence of O3 the ratio Q, {CC13CC1(0)}/@ {CC120) drops, C -is produced, and the chain length is reduced. The ratio kz/kIo = 6.7. The reduction in yield as 0, is added results from the terminating reaction t15blThe CIOz reacts further with O3 to produce C1207.The reaction of O3 with C2C14 at 24 "C also produces mainly CC13CC1(0) and CC12O with cC1, CC12b as a minor product. Other minor products detected after extended conversions included Cl,, CO, and C 0 2 . However c-C3C16 was not found. The ratio [CCI~CC~(O)]/[CC~ZO] is < 1. Moreover, the addition of O2 retarded the reaction, indicating a long chain mechanism in which both free radicals (species with an odd number of electrons) and CCl2 were absent. A diradical chain mechanism is presented which explains the main features. The chain step is the addition of CC1202 to C2C14 P5] cc1202 + c2c14 * c c I 2 o~c 2 c l 4The adduct then reacts with 0, in a chain regenerating step or with O2 in a chain terminating step.ECKART MATHIAS, EUGENIO SANHUEZA, I. C. HISATSUNE et JULIAN HEICKLEN. Can. J. Chem. 52,3852(1974).On a etudi6, a 24 et 32 "C, en presence et en absence de O,, l'oxydation initiee par des atomes de chlore de C,C14. En l'absence de O,, les produits sont CCl3CC1(0) et CCIZO; ils sont produits par un processus en chaine dans un rapport de 2.5 a 24 "C et de 3.0 a 32 "C. Les etapes amenant la formation de ces produits impliquent la decomposition des radicaux CzC150 L'adduit reagir alors avec 0, dans une Ctape regenerant la chaine ou avec 0, dans une Ctape terminant la chaine.[Traduit par le journal]

Section: Atom Oxidationsupporting

confidence: 91%

“…The chlorine atom initiated oxidation of C2C14 has been studied in several laboratories (1)(2)(3)(4), and the results reviewed (5). In all the studies, the major products were CCI,CCl(O) and CC1,O.…”

Section: Introductionmentioning

confidence: 99%

The Chlorine Atom Sensitized Oxidation and the Ozonolysis of C₂Cl₄

Mathias¹,

Sanhueza²,

Hisatsune³

et al. 1974

“…Pertinent to this work are the studies by Schumacher (18,19) and co-workers, and Dickinsorl and co-workers (20,21,22) on the photochemical chlorine sensitized oxidatioll of tetrachloroethylene. The products of the oxidatioli reaction, isolated by them, were CC13COC1 and COC12.…”

Section: Reaction Mechanismmentioning

confidence: 97%

“…The reaction was studied in the gas phase and in CC14 as solvent (21). Dickillson and Leermakers (20,21) show that the products of oxidation, CC1,COCl and COCl?, undergo little or no further oxidation or1 prolonged exposure to light. In CC14 solution the rate of oxidation of CzC14 is independent of [O?]…”

Section: Reaction Mechanismmentioning

confidence: 99%

Radiolysis of Tetrachloroethylene

Sutherland¹,

Spinks²

1959

When tetrachloroethylene is irradiated with CoeO gamma rays in the presence of oxygen or air, the main products are trichloroacetyl chloride, phosgene, and oxalyl chloride. The reaction is a chain reaction. Possible reaction mechanisms are discussed. INTRODUCTIONTetrachloroethylene, when irracliated in a two-phase aqueous system or when irradiated with a soluble pH indicator dye, liberates acidic products. The acid yields are high (GH+ values up to 6000), suggesting that a chain mechanism is operative (1, 2). Chain reactions, although highly sensitive, are often greatly influenced by dose rate, temperature, and the presence of trace impurities. In addition, this particular reaction proceeds to some degree under the iilflueilce of light (3, 4). These complicating factors, undesirable in chemical dosimetry, can'be effectively removed and in some cases totally suppressed by the addition of stabilizing reagents such as ethyl alcohol, resorcinol, and thymol. Although the sensitivity of the system to racliatioil is thereby markedly reduced (G value about 30), the use of stabilizers has made it possible to use tetrachloroethylene dosimeters which can register doses in the range, 1.0 to lo6 r and which show excellent reproducibility (1).The purpose of this study is to arrive a t a more funclamental understanding of the chain mechanism in this sytem and to see whether further study of it would be useful in interpreting some of the processes occurring when ionizing radiation interacts with matter, e.g., in providing evidence of track effects (5). EXPERIMENTALReagent grade Koclak Eastman tetrachloroetl~ylene, stabilized by the addition of 0.5% ethyl alcohol, was used as starting material. The alcohol can be removed by repeated water extractions or by fractional distillation. Pure tetrachloroethylene is prone to decompose under the influence of light and oxygen (3, 4), and thus a large sample of pure material cannot be prepared and stored for any length of time. Since this necessitates preparation of alcohol-free reagent immediately prior to each irracliation run, the following procedure was adopted.Approximately 50 ml of reagent grade tetrachloroethylene (ethyl alcohol stabilized) was shalieil with CaCl?, filtered, and fractionally distilled. The middle fraction, b.p. 120-121" C, was used. Samples which had been treated for 24 hours and 3 days, respectively, were equally sensitive to radiation. Samples which had been extracted for periods of 2 and 12 hours mere found less radiation sensitive.The system irradiated, unless stated otherwise, was a 3-ml sample of pure tetrachloroethylene overlayered with 2 ml of water which had been distilled from alkaline permanganate and then redistilled from an alkaline suspension of manganous hyclroxide. Samples were irradiated in glass-stoppered Pyrex tubes (12 X 100 mm), with gamma radiation from either a 1-curie or a 1000-curie Co60 source (6). After irradiation the solution was transferred to a 10-ml Erlenmeyer flaslc, and two 1-ml portions of wash water added. The acids libera...

“…The chlorine atom initiated oxidation of C2C1, has been studied in several laboratories (1)(2)(3)(4), and the results reviewed (5). More recently a study was made in our laboratory (6).…”

Section: Introductionmentioning

confidence: 99%

The Hg 6(³P)-Photosensitized Oxidation of C₂Cl₄

Sanhueza¹,

Heicklen²

1974

EUGENIO SANHUEZA and JULIAN HEICKLEN. Can. J. Chem. 52,3863 (1974).The Hg 6(3P) sensitized photolysis of C2C14 was studied at 25 "C both in the absence and presence of N 2 0 and 0,. For C2Cl4 alone, the only products are polymer and Hg,CI,. The quantum yield of C2C14 disappearance, -4,{C2C14} -1. Thus, the photolysis produces C2CI3 radicals and Hg2C12, the CzCI3 radicals dimerize, and the resultant 1,3-C4CI6 polymerizes. The relative quenching of Hg 6(6P) by C2CI4 compared to N 2 0 is 3.0.In the presence of 0, the products are CCI3CCI(O) and CC120 which are formed in a radical chain process in a ratio of 2.6 independent of reaction conditions. CO is also produced with a quantum yield of unity. The quantum yields of the chlorine-containing products are independent of the 0, pressure and the absorbed intensity, but are proportional to the CzCI, pressure, the proportionality constants being 1.4 and 3.7 Torr-', respectively, for CC1,O and CC13CC1(0).A detailed mechanism, based on the chlorine atom chain oxidation, is presented, and appropriate rate constant ratios are evaluated.EUGENIO SANHUEZA et JULIAN HEICKLEN. Can. J. Chem. 52,3863 (1974). On a Ctudie a 25 "C, en presence et en absence de N 2 0 et O,, la photolyse du C2C14 sensibilise par le Hg 6(3P). Lorsque le C,CI, est seul on n'isole conime produits qu'un polymere et du Hg2CIz. Le rendement quantique pour la disparition du CzC14, -cf,{C2C14), est pratiquement igal a 1. Donc la photolyse produit des radicaux C2CI3 et du Hg2C12; les radicaux C2C13 se dimerisent et le C4CI6-1,3 qui en resulte se polymCrise. La facilitk relative, pour C2C14 compare a N 2 0 , de pieger Hg 6(=P) est tgale 3.0.En presence d'oxygene les produits sont le CC13CC1(0) et le CC120 qui se forment par un processus radicalaire en chaine dans un rapport de 2.6 qui est independant des conditions reactionnelles. Du CO est aussi produit avec un rendement quantique egal a l'unite. Les rendements quantiques de produits contenant du chlore sont independants de la pression d'oxygene et de l'intensite absorbee, mais ils sont proportionnels a la pression de C2C14; les constantes de proportionnalites sont respectivelnent de 1.4 et 3.7 Torr-' pour CC120 et CC13CCI(0). On presente un mecanisme d6taillC base sur l'oxydation en chaine par les atomes de chlore; de plus on evalue les rapports des constantes de vitesse appropriees.[Traduit par le journal]