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Acetaldehyde from photolysis

Figure 2. Plot of the calculated photolysis frequencies of acetaldehyde from the entire data set against solar zenith angle. Figure 2. Plot of the calculated photolysis frequencies of acetaldehyde from the entire data set against solar zenith angle.
The cyclohexanone postulated in this scheme should also be photoactive. The series of reactions necessary to produce the acetic acid observed [11] is indeed long but currently the only reasonable explanation of this product. Previous investigators [20, 21] had not reported acetic acid from the photolysis of PET even though they isolated acetaldehyde, although Day and Wiles [25] did report it. Thus, one may reasonably assume that the presence of 1,4-cyclohexandimethanol most likely is required to produce acetic acid, at least in significant amounts. [Pg.635]

A reaction which could involve the vinyl alcohol tautomer of acetaldehyde is the synthesis of 2-(2-naphthyl)quinoline by photolysis of the anil (393) in ethanol (68TL3685). From the benzaldehyde anil of a-naphthylamine by a similar reaction, 2-phenylbenzo[Jt]quinoline... [Pg.451]

As described in Chapter 5, the natural lifetime for acetaldehyde with respect to photolysis under these conditions can be calculated from kp for the overall reaction. The natural lifetime, t, is defined as the time for the concentration of CH3CHO to fall to 1/e of its initial value, where e is the base of natural logarithms. The natural lifetime of acetaldehyde under these conditions is therefore given by r = 1 /kp = 5.5 X 106 s = 63 days. Of course, these conditions do not exist for 63 days, so the lifetime is hypothetical. However, it does provide a sort of back-of the envelope method of assessing the relative rapidity of loss of the compound by photolysis compared to other processes, such as reaction with OH. [Pg.83]

In the presence of an alcohol or ether the excited acetone abstracts an H atom from the carbon alpha to the 0 atom of the alcohol or ether. Similar photoreduction of perinaph-thenone (365) has been observed. However, the nature of the excited state of acetone for liquid photoreduction in these studies has not been established. Free radicals produced from photoreduction of acetaldehyde, biacetyl and acetoin in the presence of good H-atom donors have been observed by Zeldes and Livingston (216). These authors also studied the photolysis of oxalic acid and esters (366). [Pg.113]

Thus F. E. Blacet and J. D. Heldman, J. Am. Che n. Soc. 64, 889 (1942), and also F. E. Blacet and D. E. Leoffler, ibid.y 64, 893 (1942), found that the quantuin yield of ( 5TT4 in the photolysis of acctaldchyde-b mixtures went from about 0 at 3130 A to 0.37 at 2380 A. Since there is no chain and the (juantum yields of CO and CHsI and CII4 are all temperature-independent under these (conditions, this seems reasonable evidence for a double split of photoexcited acetaldehyde ... [Pg.384]

Khan, Norrish, and Porter decomposed acetaldehyde by means of flash photolysis. The rate of light absorption was about 10 photons/ cm. sec. Temperature rises were controlled to be between 3 and 190°C. The reactant concentration was about 10 molecules/cm., and the rate constant was about 10 . Thus the product kA is about 10 . The intersection of log kA = —I and log J = 21 is deep inside the non-chain region of Table I. Thus essentially all products are expected to arise from radical-radical reactions, or from primary photochemical reaction. The observed ratio of methane to ethane was slightly greater than two, indicating the primary process... [Pg.20]

Later these experiments were repeated -with the conclusion that Morris findings were dubious. Zemany and Burton used equimolar mixtures of acetaldehyde and acetaldehyde- /4, at temperatures 510 and 465 °C, and found that partially deuterated methanes were formed in appreciable amounts. The ratio CHD3/ CD4 was found to be 1.2 and 1.0 at 510 and 465 °C, respectively (compared to the value of 1.6 obtained in the photolysis at 140 °C). These results clearly indicate the free radical origin of the methane. However, the fact that the CHD3/CD4 ratio is lower than the one found in the photolysis made the authors conclude that there IS some contribution from the molecular mechanism. An upper limit for the latter was estimated to be approximately 15 and 25 % of the total reaction at temperatures 510and465 °C, respectively. Zemany and Burton estimated the values for the ratios methane-rf3/ethane-d6 and methane-t /ethane-rfe, from which a chain length of 1000 can be derived, at 465 °C, for the Rice-Herzfeld type decomposition. [Pg.240]

Nitric oxide inhibits the photolysis of acetaldehyde, and decreases the ratio CH4/CO from unity to a very small value. The formation of ethane is also inhibited. It may be assumed that the ratio 0n/0i can be obtained by measuring the ratio CH4/(C0-CH4) at high temperatures in the presence of NO. The values, determined in this manner at 300°C, are 0.08 and 0.21 at 3130 Aand 2537 A, respectively. At 2537 A, the agreement with the iodine-inhibition experiments is poor. [Pg.280]

Recent investigations on ethane formation in the photolysis of acetaldehyde indicate that decomposition into methyl and formyl radicals occurs from the triplet state which is also removed by first-order internal conversion and, to some extent, by second-order deactivation. In the mercury-photosensitized reaction methyl radicals are formed by direct dissociation of the excited aldehyde molecules, as well as by collision of excited mercury atoms . [Pg.285]

The role of the triplet state at 3130 A was investigated by Cundall and Davies , by measuring the isomerization ot the added cw-butene-2. As is known, cw-butene-2 transfers energy from the triplet acetone molecule while the olefin molecule itself is isomerised. The same was observed in the photolysis of acetaldehyde, where it was found that with increasing concentration of the added olefin, the cis-butene-2 triplet yield, increased to a limiting value of approximately 0.4 at 48 °C at the same time < co approached zero (or a value below 0.02). At 100 °C, a somewhat lower value was obtained for < bt ... [Pg.285]

Below, some of the results concerning the pressure dependence of the radical decomposition and recombination processes will be discussed. No deviation was observed from the second-order kinetics of the termination step in the experiments of Grahame and Rollefson , while Dodd S found it necessary to consider the pressure dependence of the methyl recombination at around 10 torr. Dorman and Buchanan came to the conclusion that the decomposition of the formyl radical is in its pressure-dependent region below a few atm, whilst that of the acetyl radical seems to be pressure-dependent below about 50 or 150 torr. The results of Style and Summers also indicate the formyl radical decomposition to be pressure-dependent under the conditions where the photolysis of acetaldehyde was usually studied. [Pg.287]

Dodd , as well as Ausloos and Steacie applied relation (35) to the experimental results of acetaldehyde photolysis. The data obtained at high temperatures seem to fit the Arrhenius straight line derived from the azomethane-acetaldehyde and di-/-butyl peroxide-acetaldehyde systems. At low temperatures, however, considerable deviation from this line could be observed, the possible result of additional methane producing reactions of some sort. According to Dodd, these processes could be (i) primary process II, (//) disproportionation reaction (26) and (in) the wall reaction of the methyl radicals. [Pg.294]

This is similar to the mechanism postulated by Kwei for the production of the P chloro ketones. It is also possible that this absorption is due to the acetyl fragments split off by type I photolysis. We have observed that the carbonyl absorption at 1770 cm can be removed by reprecipitation from THF solution by methanol. This indicates that the groi ) responsible for this absorption is not chenoically attached to the molecule. The acetyl radical produced by the type I can abstract hydrogen, or chlorine, either from the polymer or the stabilizer to form either acetaldehyde or acetyl chloride which may hydrolyze to the acid. [Pg.279]

The photolysis of dimethyl and diethyl ethers in the gas phase was first studied by Harrison and Lake (172) using a hydrogen discharge lamp. They reported the formation of formaldehyde from dimethyl ether, and ethylene, acetaldehyde, and formaldehyde from diethyl ether. [Pg.91]

The main products from the ethylene oxide photolysis at wavelengths above 170 nm are carbon monoxide and hydrogen (193, 194). Ethane and methane, and sometimes acetaldehyde, formaldehyde, and ethylene, are major products (Table 16). Ketene has also been detected (90). Ethylene shows a strong increase when the photolyzing light is below 170 nm (195). Comer and Noyes (193) had concluded that the major primary process was reaction 1 in Scheme 12. This was confirmed by Roquitte (194), who showed a minor contribution from process 2, and recently by Kawasaki et al. (195) in their detailed study at different wavelengths... [Pg.99]

Some preliminary results from the reviewers laboratory (293) may shed light on the mechanism of the ethylene and carbon dioxide formation. The liquid phase photolysis (185 nm) of 2,2-dimethy1-1,3-dioxolane affords large quantities of ethylene and some carbon dioxide. Carbon dioxide is also formed if di-t-butyl-peroxlde is photolyzed in 2-methyl-l,3-dloxolane. Thus it seems probable that in the primary process the l,3-dioxolanyl-2-radical is formed. The latter appears to be prone to fragmentation and further eliminates ethylene to give rise to a 0=CR-0 radical, a likely precursor of the carbon dioxide. This sequence is not possible in the open chain acetals. In agreement with this, carbon dioxide is not a product in the photolysis (185 nm) of liquid formaldehyde and acetaldehyde dimethyl acetal (103a,b). [Pg.105]

To obtain a clear dependency a statistical treatment of all the calculated photolysis frequencies, derived from all the actinic spectra recorded in the EUPHORE chamber has been performed. Figure 3 shows an example of the complete dataset for acetaldehyde. The statistical treatment has allowed a clear dependency between the calculated photolysis frequency and the solar zenith angle to be established. The result obtained for acetaldehyde statistical treatment after is presented graphically in Figure 4. The error bars represent the statistical (la) error only. Photolysis frequencies have been calculated in the range of 19 to 71.5 solar zenith angles for 17 carbonyl compounds. The calculated photolysis frequencies obtained for the different zenith angles as derived from all the EUPHORE actinic flux spectra measurements are presented in Table 1. [Pg.123]

Apart from a small seeondary influence of the changes in the HCHO photolysis parameters, no further modifications were required to the acetaldehyde mechanism. As shown in Figure 4 to Figure 7, MCM v3a provides a very good description of D(03-NO) in the complete set of CH3CHO-NOX chamber experiments. [Pg.246]

Zeldes, H., and if. Livingston Magnetic Resonance Studies of Liquids during Photolysis, IV Free Radicals from Acetaldehyde, Diacetyl and Acetoin. J. Chem. Phys. 47, 1465 (1967). [Pg.83]

Propanol. 2-Propanol was chosen as a model for a simple alcohol. Irradiation under vacuum gave hydrogen and acetone as major products along with smaller amounts of methane, acetaldehyde, carbon monoxide, tert-butyl alcohol, and ethanol. These minor products must arise mainly from acetone. Acetaldehyde may be formed either by direct photolysis of 2-propanol, hydrogen atom abstraction by acetyl radical, or /3-scission of the 2-propyloxy radical. The formation of tert-butyl alcohol implies the presence of methyl and 2-hydroxy-2-propyl radicals. [Pg.93]

Carbonyl compounds, carboxylic acids, and esters of a wide variety of types have been isolated from surface waters. Aldehydes and ketones are produced during the photolysis of larger polymers such as humic materials formaldehyde, acetaldehyde, and glyoxal appear to be the most abundant in seawater samples (Kleber and Mopper, 1990). Low molecular weight mono-, di-, and tricarboxylic acids such as acetic, formic, lactic, glycolic, malic, and citric acids have been reported by many investiga-... [Pg.53]


See other pages where Acetaldehyde from photolysis is mentioned: [Pg.1080]    [Pg.105]    [Pg.107]    [Pg.124]    [Pg.122]    [Pg.73]    [Pg.35]    [Pg.204]    [Pg.553]    [Pg.293]    [Pg.184]    [Pg.62]    [Pg.79]    [Pg.85]    [Pg.287]    [Pg.10]    [Pg.87]    [Pg.90]    [Pg.470]    [Pg.93]    [Pg.320]    [Pg.105]   
See also in sourсe #XX -- [ Pg.2 , Pg.2 , Pg.2 , Pg.288 ]




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Acetaldehyde photolysis

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