14C ethylene

Fig. 6. Adsorption isotherms for 14C-ethylene and the effect of hydrogen on the adsorbed species for (a) nickel—alumina and (b) palladium—alumina at 20°C [63],...

The co-existence of at least two modes of ethylene adsorption has been clearly demonstrated in studies of 14C-ethylene adsorption on nickel films [62] and various alumina- and silica-supported metals [53,63—65] at ambient temperature and above. When 14C-ethylene is adsorbed on to alumina-supported palladium, platinum, ruthenium, rhodium, nickel and iridium catalysts [63], it is observed that only a fraction of the initially adsorbed ethylene can be removed by molecular exchange with non-radioactive ethylene, by evacuation or during the subsequent hydrogenation of ethylene—hydrogen mixtures (Fig. 6). While the adsorptive capacity of the catalysts decreases in the order Ni > Rh > Ru > Ir > Pt > Pd, the percentage of the initially adsorbed ethylene retained by the surface which was the same for each of the processes, decreased in the order... 

With alumina-supported palladium, platinum and rhodium and silica-supported platinum [65,66] in the temperature range 20—200°C, no molecular exchange between adsorbed 14C-ethylene and gaseous ethylene is observed, whilst with hydrogen, small quantities of methane are formed at 100°C and above with platinum and rhodium and at 200° C withpallad-... 

Fig. 27. 14C-acetylene adsorption isotherm on palladium—silica at 20°C (O) and the 14C-ethylene adsorption isotherm on an acetylene-precovered palladium—silica catalyst... 

Somorjai80 studied the formation of irreversible coke from 14C ethylene on Pt (111) from 50 to 400°C and found that 75% was irreversible at the point where the H/C decreases to 0.2. This leads to graphitisation of the coke, and its inability to desorb and migrate. 

The cooxidation at 199 °C of C2H4 together with [l,2-14C]ethylene oxide and the cooxidation at 215 °C of C3H6 with [2-14C]propylene oxide over a silver catalyst showed no oxygen exchange between olefin and epoxide, but a certain portion of C02 was produced by destruction of the product epoxide (2% of C02 was produced from oxidation of propylene oxide and about 10% from ethylene oxide). 

Only two examples of standard copolymers with 14C- abelled propylene have been reported (29, 72). In one study (72) they had to be used because of the low C3 concentration range (0—10% by moles) covered by calibration. (We shall deal with this subject later, since we think that this is an inappropriate choice of analytical band.) The other paper (29) dealing with 14C-labelled C3 contains the remarkable conclusion that comparison of two sets of copolymers prepared with 14C-ethylene and l4C-propylene, respectively, ruled out any possibility of anomalous isotope effects on the polymerization. 

Br14CH2-14CH2OH is obtained in 90% yield from [14C]ethylene by use of A-bromo-acetamide.294... 

C Primary kinetic isotope effects for the concerted reaction of butadiene with ethylene, for the stepwise reaction of butadiene with ethylene and for the concerted reaction of butadiene with acrolein, have also been calculated207. The experimental values of 1.0438 and 1.0474 found recently196 in the reaction of 2,3-dimethylbutadiene with [1-14C]- and [2-14C]-l-nitro-2-phenylethylene, respectively, similar at both reacting termini, are in accord with the calculated value of 1.046 for knc/ki4c (373.15 K) in a synchronous concerted reaction of butadiene with ethylene. The 14C KIE values predicted for the asynchronous acrolein reaction are 1.015 and 1.045 for the T and 2 isotopomer, respectively207. 

There is a basic rule that applies to production in the chemical industry invest huge capital to make a big plant so that there is less overhead and the product can be produced more cheaply on this larger scale. This is the principle of economy of scale. A typical ethylene plant capacity rose from 70 million Ib/yr in 1951 to 2 billion Ib/yr in 1991. In 1950 vinyl chloride sold for 14C/lb and was produced at a rate of 250 million Ib/yr. In 1969 it sold for 5C/lb (in spite of 20 years of inflation) because it was being made at the rate of 3.6 billion Ib/yr. In 1950 sulfuric acid, the number one chemical in terms of U.S. production, sold for 20/ton. In 1980 the price was only 40/ton despite many double-digit inflation years in the 1970s. The reason is that the production went from 20 billion lb to 80 billion lb. 

Gessner PK, Parke DV, Williams RT, et al. Studies in detoxication. 86. The metabolism of 14C-IabeIIed ethylene glycol. Biochem J 1961 79 4S2MS9. 

C-Propene adsorption on platinum—alumina and platinum—silica [66] differs from ethylene adsorption insofar as a fraction of the initially retained 14C-propene is relatively easily exchanged or removed by hydrogen treatment. This suggests less extensive dissociation of the adsorbed propene and a 7T-allyl species (structure F) has been proposed in this case, viz. 

These studies also showed that, on a surface effectively saturated with 14C-propene, ethylene adsorption could still occur, although the amount... 

C-Tracer studies of acetylene adsorption on alumina- and silica-sup-ported palladium [53,65], platinum [66] and rhodium [53] show the coexistence of at least two adsorbed states, one of which is retained on the surface, the other being reactive undergoing molecular exchange and reaction with hydrogen. Acetylene adsorption exhibits the same general characteristics as those observed with ethylene (see Sect. 3.2). However, there are important differences. The extent of adsorption and retention is substantially greater with acetylene than with ethylene. Furthermore, the amounts of acetylene retained by clean and ethylene-precovered sur-... 

This is the Verdrangungsreaktion with the monomer, and it is catalyzed by the Ziegler catalyst or its consecutive products. Using aluminum alkyls and 14C-labeled ethylene, under conditions not causing any insertion or hydride formation and in the presence of a dead catalyst, an equilibrium distribution of labeled ethylene between the gas phase and the alkyl is reached (33). It has been possible in certain cases to use this effect to reduce molecular weight from over l million to some hundreds by increasing the temperature from 25 to 100°C without any loss in efficiency (34). 

It is remarkable that a reduced Ziegler type of catalyst that is no longer reactive for ethylene polymerization causes the exchange between 14C-labeled ethylene and the alkyl groups of the triethylaluminum until the equilibrium point is reached. The intermediate structures mentioned were only detected spectroscopically because of their low stability, they were not isolated. 

Woody, Lewis, and Wills 72> studied the disproportionation of [1-14C] propylene over cobalt oxide-molybdate-alumina at 149 and 177 °C. Approximately equal amounts of radioactivity were found in the approximately equal molar quantities of ethylene and butene. These results are in agreement with those of Clark and Cook showing that double-bond isomerization was a factor in this temperature region. Woody and coworkers suggest that since the isomerization of the 2-butene product was negligible, an explanation of double-bond mobility as simple isomerization is probably an oversimplification. 

Radioisotope detection of P, 14C, and Tc was reported by Kaniansky et al. (7,8) for isotachophoresis. In their work, isotachophoretic separations were performed using fluorinated ethylene-propylene copolymer capillary tubing (300 pm internal diameter) and either a Geiger-Mueller tube or a plastic scintillator/photomultiplier tube combination to detect emitted fi particles. One of their reported detection schemes involved passing the radiolabeled sample components directly through a plastic scintillator. Detector efficiency for 14C-labeled molecules was reported to be 13-15%, and a minimum detection limit of 0.44 nCi was reported for a 212 nL cell volume. 

Cl (12), I (13), N (14), Si (9), other polyvalent atoms (15), and of muonium (16). Reviews have also been published on the reactions of recoil atoms with arenes (17), (halo)ethylenes (18), and (halo)-methanes (19). The capture of ir in hydrogenated species is sometimes considered as a part of recoil chemistry (20), and so also are reactions of species formed after decay of multiply labeled (T, 14C) molecules (21-23), for example,... 

Figure 4-28. The tt- complexes of ethylene formed from the 6-member chelate (after methyl acrylate insertion) with the model (14, 14a, 14b, 14c) and real catalyst (14, 14a )...

Figure 4-30. Changes in the interatomic distances for M-O (carbonyl) and M-Hg(M = Ni, Pd) along die MD trajectory obtained from die ethylene insertion starting from die complex 14c [top] and examples of the structures observed along die trajectory [bottom] S denotes a reaction progress variable...

The new antihypertensive agents 194 and 195, which function in part through interaction with a-andrenoreceptors198, have been 14C-labelled199 in three steps starting from ethylene-14C2 oxide (equation 77). The overall radiochemical yields for 194 and 195 were 69% and 62%, respectively, and the specific activities of both compounds before final dilutions were initialy 22.6 mCi mmol-1. 

---