Crotonaldehyde, atmosphere

Acetaldehyde condenses in the presence of a little sodium sulphite or sodium hydroxide solution to aldol. The latter ehminates water upon distUlation at atmospheric pressure, but more efficiently in the presence of a trace of iodine, which acts as a catalyst, to yield crotonaldehyde ... 

Properties Water-white to pale yellow, syrupy liquid. Decomposes into crotonaldehyde and water on distillation under atmospheric pressure. Miscible with water, alcohol, ether, organic solvents. D 1.1098 (15.6/4C), bp 83C (20 mm), vap press less than 0.1 mm (20C), specific heat 0.737, bulk d 9.17 lb/gal (20C), fp below 0C. Flash p 150F (65.5C) (OC), autoign temp 530F (276.6C). Combustible. 

The reaction did not require dry solvents or inert atmosphere and afforded the desired adducts in 42-98% yield. As expected, the more reactive acrolein and methyl vinyl ketone gave very good results with both acyclic and cyclic p-ketoesters and p-diketones and, surprisingly, acrylonitrile and methyl acrylate, reported to be totally inactive under Lewis acid catalysis, " afforded the corresponding adducts with a-acetylbutyrolactone in high yield (77 and 98% respectively). In the reaction with crotonaldehyde, a 1 1 mixture of... 

The activity of the catalysts was tested in the hydrogenation of crotonaldehyde, cinnamaldehyde and furfural at atmospheric pressure. Before the reaction, the catalysts were reduced in a stream of dihydrogen at 623 K. Hydrogenation reactions were carried out in a standard fixed bed vertical reactor. After the catalyst reduction, the reactor was cooled down to the reaction temperature (423, 470 or 523 K) and unsaturated aldehyde and hydrogen were introduced onto the top of the reactor. The first product sample for analysis was taken after 30 min of reaction (period needed to reach reaction steady state). The identification and analysis of the reaction mixtures were performed by means of GC-MS using HP-50 capillary column. 

All catalysts were evaluated at steady-state conditions in a one atmosphere flow reactor using gas flows of He, C4H6, and O2, which were delivered by mass flow controllers. For the kinetic dependency studies, CO2 was also added by a mass flow controller, while different levels of epoxybutene and H2O were introduced from a helium-swept vapor-liquid saturator. In a similar manner, furan, epoxybutene, 2,5-dihydrofuran and crotonaldehyde were added to the feed stream... 

In the present work a large set of actinic spectra recorded in the EUPHORE chamber under various atmospheric conditions has been obtained and used for the calculation of photolysis frequencies of 17 organic carbonyl compounds. From a statistical analysis of the photolysis frequencies calculated for the compounds an analytical form for Jfd) has been derived. For unsaturated compounds (methyl vinyl ketone, methacrolein, acrolein and crotonaldehyde) < ) g is negligible, although those cxompounds possess absorption spectra reaching the near visible. 

These compounds, exemplified by acrolein, crotonaldehyde, and methyl vinyl ketone, are known to react with ozone and with OH radicals. Photolysis and N03 radical reaction are of minor importance. Under atmospheric conditions the 03 reactions are also of minor significance (Atkinson and Carter, 1984), leaving the OH radical reaction as the major loss process. For the aldehydes, OH radical reaction can proceed via two reaction pathways OH radical addition to the double bond and H-atom abstraction from the -CHO group (Atkinson, 1989). For crotonaldehyde, for example, the OH reaction mechanism is given in Fig. 3. As can be noted from Fig. 3, these a,/3-unsaturated aldehydes are expected to ultimately give rise to a-dicarbonyls such as glyoxal and methylglyoxal. For the a,/3-unsaturated ketones such as methyl vinyl ketone, the major... 

Ir/Ti02 catalyst was studied in gas-phase crotonaldehyde hydrogenation at atmospheric pressure and 353 K. Strong deactivation was observed. However up... 

The gas phase hydrogenation of crotonaldehyde (2-butene-l-al from Aldrich, purity > 99.5%, used without further purification) was carried out in a quartz glass tubular reactor under atmospheric pressure. Typically, 1-10 mg of the chloride precursor were loaded into the reactor. In order to obtain a suitable catalyst bed... 

Crotonaldehyde on hydrogenation over nickel catalyst at atmospheric pressure and 25°C in the presence of chloroform gives butyraldehyde as the major product in the absence of chloroform, butyl alcohol is formed. 

Carbonyl compounds are probably present at low levels in all air samples (Fung and Grosjean, 1981). A great variety of combustion processes produce aldehydes they are particularly abundant in wood smoke, and have also been identified in the products of combustion of natural gas and fuel oil, and in engine exhaust samples. It is likely that they are relatively long-lived intermediates in atmospheric photooxidation reactions. Formaldehyde (CH2O), for example, is always an obligatory intermediate in the conversion of methane to CO2. In nearly all air samples so far examined, formaldehyde has been the most abundant aldehyde, with acetaldehyde, pro-pionaldehyde, acrolein, benzaldehyde, crotonaldehyde, and furfural sometimes present at much lower concentrations (Kuwata et al., 1979 Penkett, 1982 Zhou and... 

After screening several reductants in the aerobic epoxidation of olefins catalyzed by nickel(II) complexes, it was found that an aldehyde acts as an excellent reductant when treated under an atmospheric pressure of molecular oxygen at room temperature (Scheme 6). Similar reactions have been reported in the patents. Propylene was monooxygenated into propylene oxide with molecular oxygen in the coexistence of metal complexes and aldehyde such as acetaldehyde " or crotonaldehyde, but the conversion of olefin and the selectivity of epoxide were never reached satisfactory levels. Recently, praseodymium(III) acetate was also shown to be an effective catalyst for the aerobic epoxidation of olefins in the presence of aldehyde. ... 

Touroude and collaborators studied the selective hydrogenation of crotonaldehyde on 5 wt% Pt/Ce02 in the gas phase at atmospheric pressure. " The properties of the catalysts and their catalytic... 

Cycloadditions of crotonaldehyde N,N-dimethylhydrazone 154 with naphthoquinone 155 at room temperature afforded cycloadduct 156 in yields superior to atmospheric pressure conditions (Scheme 38) [59]. Interestingly, elongation of pressurizing time from 6 to 24 h diminishes the yield of azaanthraquinone, as aminoquinone side products 157 and 158 are formed. 

A similar mechanism leads to the formation of acrolein, CH2=CHCHO, from 1,3-butadiene. Unsaturated aldehydes are also directly emitted to the atmosphere, for example crotonaldehyde, CH3CH=CHCHO, is emitted in substantial quantities from noncatalyst-equipped gasoline and diesel vehicles (see chapter I). 

Salgado, M.S., E. Monedero, F. Villanueva, R Martin, A. Tapia, and B. Cabanas (2008), Night-time atmospheric fate of acrolein and crotonaldehyde. Environ. Sci. TechnoL, 42, 2394-2400. 

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