0- acroleins

Acrolein rarely features as the activated olefins in the MBH reaction with aldehydes, clearly because of its propensity to form oligomers or polymers under the basic catalysts employed. However, this hurdle has been surmounted by selection of appropriate reaction conditions. The DABCO-catalyzed addition of acetaldehyde and propionaldehyde with acrolein proceeded in good yields under a low catalyst concentration, perhaps to minimize the polymerization of acrolein. It is also the exclusive path in the attempted addition of 2-pyridinecarboxaldehyde and a-diketones to acrolein. In addition, successful MBH reactions of acrolein with aldehydes have been reported xmder high pressure, which affected a dramatic acceleration in the rate of MBH reaction. More reactive electrophiles, including halo ketones, fluoro-carbonyls and activated imines,all reacted very rapidly with acrolein. 

Acrolein was the only aldehyde used as a war gas during the war of 1914-18, and its use was very limited as it was soon superseded by other substances having superior offensive properties. 

Acrolein, or acrylic aldehyde, was prepared by Redtenbacher in 1843, and was first used as a war gas by the French in 1916, being suggested by Le Pape, whence its name of Papite. However, it was not very efficient, chiefly because of its tendency to polymerise into substances having no irritant action. 

Acrolein is usually obtained from glycerol by abstraction of 2 molecules of water  

The following may be employed as dehydrating agents phosphoric acid, boric acid, potassium bisulphate, sodium sulphate, etc. However, the preparation of acrolein is not very satisfactory when these substances are used, the yield being not above 30-40% of the theoretical. It was only as a result of the 

Little is known concerning the action of the acid sulphates on glycerol. A recent theory suggests that salts of glycero-sulphuric acid are first formed  

Acrolein (2-propenal, CH2=CHCHO, freezing point -87°C, boiling point 52.7°C, density 0.8427, flash point -18°C) is the simplest unsaturated aldehyde. The primary characteristic of acrolein is its high reactivity due to conjugation of the carbonyl group with a vinyl group. 

Acrolein is a highly toxic material with extreme lachrymatory properties. At room temperature acrolein is a liquid with volatility and flammability somewhat similar to those of acetone, but, unlike acetone, its solubility in water is limited. Commercially, acrolein is always stored withhydroquinone and acetic acid as inhibitors. 

The first commercial process for manufacturing acrolein was based on the vaporphase condensation of acetaldehyde and formaldehyde. 

Catalyst developments led to a vapor-phase processes for the production of acrolein in which propylene was the starting material. 

The catalytic vapor-phase oxidation of propylene (Fig. 1) is generally carried out in a fixed-bed multitube reactor at near atmospheric pressures and elevated temperatures (ca 350°C) molten salt is used for temperature control. Air is commonly used as the oxygen source and steam is added to suppress the formation of flammable gas mixtures. Operation can be single pass or a recycle stream may be employed. 

Acrolein (CH2=CH-CHO) is a more irritating aldehyde than formaldehyde on account of its unsaturated nature. It irritates eyes and mucous membranes of the respiratory tract already at concentrations below 1 ppm. 

The acrolein effect on the breathing system was also followed in guinea pigs [39]. It was found that during an exposure to 0.6 ppm and above, the degree of the pulmonary flow resistance and the respired air volume are increased, with decreasing breathing frequency. The acrolein effects were reversible. 

The inhalation of acrolein also affected certain enzymes of the rat liver 

Mankind encountered the effects of carbon monoxide as far back as prehistoric times. It is the most common poison with a suffocation action. It is second to carbon dioxide with respect to the amounts of industrial emissions. Carbon monoxide toxicity is due to its affinity to haemoglobin. This affinity is higher by a factor of 200 than that of oxygen. Haemoglobin 

Besides this main effect, which leads to suffocation, carbon monoxide also exerts other effects. They are, however, of a lower importance in a comparison with the effect on haemoglobin. It is possible to consider effects on myoglobin and on the other tetrapyrol substances. Many enzymes containing trace elements modify their activity by the action of carbon monoxide [41]. An increase of the activity of aspartate-aminotransferase and of the lactate concentration can be used for the indication of acute poisoning [42]. 

Acrolein enters the aquatic environment from its use as an aquatic herbicide, industrial discharges, and as a by-product of the chlorination of organic compounds in wastewater and drinking water treatment. 

Eisler, R. 1994. Acrolein hazards to fish, wildlife, and invertebrates a synoptic review. U.S. Natl. Biol. Surv. Biol. Rep. 23.29 pp. 

Eisler, R. 2000. Acrolein. Pages 739-766 in Handbook of Chemical Risk Assessment Health Hazards to Humans, Plants, and Animals. Volume 2, Organics. Lewis Publishers, Boca Raton, Florida. 

Acrolein is an extremely reactive molecule that is used to perform several different functions in the oilfield. It is an effective biocide at low use concentrations and will also reduce hydrogen sulfide concentrations. It is also used in squeeze treatments to aid in the dissolution of iron sulfide. 

Mechanism of action. Acrolein has two functional groups that can contribute to its biocidal activity. It is an a, jS-unsaturated aldehyde and as such the carbon-carbon double bond is extremely reactive. Nucleophiles, typically sulfur based nucleophiles, can react with the terminal carbon in a Michael type reaction (March, 1992), while the aldehyde group can undergo reactions typical of all aldehydes. From a biocidal point of view, those sulfur-based nucleophiles would include cysteine residues of the cell wall and those proteins associated with the cell wall. The amine containing amino acids (lysine and arginine) may also react with the aldehyde group of acrolein. 

Zdt-Umsatz-Kurven fur die kathodische Polymerisation von Acrolein bei verschiedenen Stromstarken. 0° C, Monomerkonzentration 12%, LSsungsmittel Tetrahydrofuran, Elektrolyt Natriumtetraphenylborat (7) 

Kathodisch gebildete Polyacrylnitrilmenge (tn als Funktion der Elektrolysendauer in strong wasserfrden Systemen. 25° C, Stromst ke 2 mA, Elektrolyt Tetraathylammoniumperchlorat (4) 

EinfluB des Wasscrgehalts auf die elektrodtetnische Polymerisations-ausbeute (Med Monomeres/Faraday) bd der kathodischen Potymerisation von A lnitrfl. 15° C, Elektrolyt Tetramethylammoniumpercfalorat (4) 

EinfluB des Wassergehalts auf die Staudingerindices des bei do- kathodischen Polymerisation von Acrylnitril entstehenden Polymeroi. 15° C, Elektrolyt Tetramethylammoniumperchlorat (4) 

Ixsitzt, deren Zustandekommen dutch die normale Wachstumsreaktion 

Ammoxidation of propylene is considered under oxidation reactions because it is thought that a common allylic intermediate is formed in both the oxidation and ammoxidation of propylene to acrolein and to acrylonitrile, respectively. 

The use of peroxides for the oxidation of propylene produces propylene oxide. This compound is also obtained via a chlorohydrination of propylene followed by epoxidation. 

Acrolein (2-propenal) is an unsaturated aldehyde with a disagreeable odor. When pure, it is a colorless liquid, that is highly reactive and polymerizes easily if not inhibited. 

The main route to produce acrolein is through the catalyzed air or oxygen oxidation of propylene. 

Transition metal oxides or their combinations with metal oxides from the lower row 5 a elements were found to be effective catalysts for the oxidation of propene to acrolein. Examples of commercially used catalysts are supported CuO (used in the Shell process) and Bi203/Mo03 (used in the Sohio process). In both processes, the reaction is carried out at temperature and pressure ranges of 300-360°C and 1-2 atmospheres. In the Sohio process, a mixture of propylene, air, and steam is introduced to the reactor. The hot effluent is quenched to cool the product mixture and to remove the gases. Acrylic acid, a by-product from the oxidation reaction, is separated in a stripping tower where the acrolein-acetaldehyde mixture enters as an overhead stream. Acrolein is then separated from acetaldehyde in a solvent extraction tower. Finally, acrolein is distilled and the solvent recycled. 

Many studies that characterized carbohydrate fermentation patterns applied methods that focused on utilization of single carbohydrates (Davis etal., 1988 Edwards and Jensen, 1992 Edwards etal., 1993 1998a 2000). It is therefore possible that these bacteria can metabolize glycerol to acrolein if other sugars or lactic acid are present. NADH produced as a byproduct of carbohydrate (or lactate) utilization is speculated to be reoxidized to NAD from the reduction of 3-HPA to 1,3-propandiol (Schiitz 

Synonyms Acrylaldehyde 2-propenal allyl aldehyde propylene aldehyde Aqualin 

Intermediate in the manufacture of acrylic acid herbicide algicide in pharmaceuticals, perfumes, food supplements, and resins as a warning agent in methyl chloride refrigerating systems 

Toxicology. Acrolein is an intense irritant of the upper respiratory tract, eyes, and skin. 

Exposure to high concentrations may cause tracheobronchitis and pulmonary edema. The irritation threshold in humans is 0.2 5-0.5 ppm, and concentrations above Ippm are extremely irritating to all mucous membranes within 5 minutes. Fatalities have been reported at levels as low as 10ppm, and 150 ppm was lethal after 10 minutes. The violent irritant effect usually prevents chronic toxicity in humans. Skin contact causes irritation, burns, and epidermal necrosis. Eye splashes cause corneal damage, palpebral edema, blepharoconjunctivitis, and fibrinous or purulent discharge.  

In experimental animals the respiratory system is a primary target of acrolein exposure after inhalation, and there is an inverse relationship between the exposure concentration and the time it takes for death to occur. Inhalation LCso values of 327ppm for 10 minutes and 130ppm for 30 minutes have been reported in rats. Of 57 male rats, 32 died after exposure to 4 ppm for 6 hours/day for up to 62 days. Desquamation of the respiratory epithelium followed by airway occlusion and asphyxiation is the primary mechanism for acrolein-induced mortality in animals. Sublethal acrolein exposure in mice at 3 and 6 ppm suppressed pulmonary antibacterial defense mechanisms. A combination of epithelial cell injury and inhibition of macrophage function may be responsible for acrolein-induced suppression of pulmonary host defense.  

Yapor Density Vapor Pressure Flash Point 

Pungent, lacrimatory, intensely irritating odor detectable at 0.02 to 0.4 ppm 

Highly toxic causes severe irritation and corrosion of skin, eyes, nose, and respiratory system highly flammable may polymerize violently upon loss or removal of inhibitor or initiation by chemical agents. 

Acrolein is mutagenic in bacteria but did not cause increased tumor incidence in animals exposed chronieaUy by injection or inhalation. Administration to pregnant rats caused malformations and lethality to embryos. Chronic exposure to as little as 0.21 ppm acrolein caused inflammatory changes in lungs, liver, kidneys, and brains of experimental animals. 

Acrolein is a highly flammable liquid (NFPA rating = 3) and its vapor can travel a considerable distance and flash back. Acrolein vapor forms explosive mixtures with air at concentrations of 2.8 to 31% (by volume). Carbon dioxide or dry chemical extinguishers should be used for acrolein fires. 

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When the fats are heated above 250"C they decompose with the production of acrolein, the intense smell of which is one of the best methods for detecting fats. The extraction of fats from tissues is most conveniently carried out by extraction with ether or some other solvent. 

HC CH(0H) CH20H. optically active. D-glyceraldehyde is a colourless syrup. May be prepared by mild oxidation of glycerol or by hydrolysis of glyceraldehyde acetal (prepared by oxidation of acrolein acetol). DL-glyceraldehyde forms colourless dimers, m.p. IBS-S C. Converted to methylglyoxal by warm dilute sulphuric acid. The enantiomers... 

When exposed to sunlight, it is converted to a white insoluble resin, disacryl. Oxidized by air to propenoic acid small amounts of hy-droquinone will inhibit this. Bromine forms a dibromide which is converted by barium hydroxide into DL-fructose. The acrid odour of burning fats is due to traces of propenal. It is used in the production of methionine and in controlled polymerization reactions to give acrolein polymers. ... 

When a mixture of aniline, nitrobenzene, glycerol and concentrated sulphuric acid is heated, a vigorous reaction occurs with the formation of quinoline. It is probable that the sulphuric acid first dehydrates the glycerol giving acrolein or acraldehyde (A), which then condenses at its double bond with the amino group of the aniline to give acrolein-aniline (B), The latter in its enol... 

I. Acrolein test. Heat 0-5 ml. with about i g. of finely powdered KHSO4. Acrolein, CH2 CH CHO, produced by dehydration of the glycerol, is readily detected by its characteristic and irritating odour smell cautiously). 

If the original ester is a fat or oil and produces an odour of acrolein when heated, it may be a glyceride. Esters of ethylene glycol and of glycol with simple fatty acids are viscous and of high b.p. They are hydrolysed (method I) and the ethyl alcohol distilled ofl. The residue is diluted (a soap may be formed) and acidified with hydrochloric acid (Congo red paper). The acid is filtered or... 

Benzaldehyde is easily oxidised by atmospheric oxygon giving, ultimately, benzoic acid. This auto-oxidation is considerably influenced by catalysts tiiose are considered to react with the unstable peroxide complexes which are the initial products of the oxidation. Catalysts which inhibit or retard auto-oxidation are termed anti-oxidants, and those that accelerate auto-oxidation are called pro-oxidants. Anti-oxidants find important applications in preserving many organic compounds, e.g., acrolein. For benzaldehyde, hydroquinone or catechol (considerably loss than U-1 per cent, is sufficient) are excellent anti-oxidants. 

Figure 1.3. Frontier orbital energies (eV) and confidents for acrolein and protonated acrolein. In the latter case the upper numbers refer to the situation where bond lengths and angles correspond to those of acrolein. The lower numbers are more suitable for a hydroxyallyl cation. The actual situation is assumed to be intermediate. The data are taken from ref. 104.

To a mixture of 250 ml of ether and 3 moles of freshly distilled acrolein ivere added about 3 moles of bromine at a rate such that the temperature could easily be maintained between -30 and -90°C (bath of dry-ice-acetone or liquid Nj). After persisting of the browncolour, the temperature was allowed to rise to 0°C. Freshly distilled ethyl orthoformate (3.25 moles) and 96% ethanol (30 ml) were added. 

Reaction of triethylsilane with a, /3-unsaturated aldehydes catalyzed by Pd on carbon gives a /raff5-l,4-adduct as the main product. Reaction of acrolein gave the adduct in 86% yield, in which the 1,4-adduct 48 was 97% and the 1,2-adduct was 3%[44]. 

Addition of nucleophiles to both activated and unactivated alkenes is catalyzed by Pd(II). Addition of alcohols or AcOH to alkenes bearing EWGs is catalyzed by PdCl2(PhCN)2 to give the corresponding ethers and esters. The addition of an alcohol to the cyclic acetal of acrolein 82 to give the ether 83 is also possible with the same catalyst[64]. Amines add to the vinylic ether 84 to give 85, but not to simple alkenes[65]. 

Donor substituents on the vinyl group further enhance reactivity towards electrophilic dienophiles. Equations 8.6 and 8.7 illustrate the use of such functionalized vinylpyrroles in indole synthesis[2,3]. In both of these examples, the use of acetyleneic dienophiles leads to fully aromatic products. Evidently this must occur as the result of oxidation by atmospheric oxygen. With vinylpyrrole 8.6A, adducts were also isolated from dienophiles such as methyl acrylate, dimethyl maleate, dimethyl fumarate, acrolein, acrylonitrile, maleic anhydride, W-methylmaleimide and naphthoquinone. These tetrahydroindole adducts could be aromatized with DDQ, although the overall yields were modest[3]. 

FIGURE 18 6 Acrolein w (H2C=CHCH=0) is a planar molecule Oxygen and each carbon IS sp hybridized and each contributes one elec tron to a conjugated tt elec tron system analogous to that of 1 3 butadiene... 

Acrolein (H2C=CHCH=0) reacts with sodium azide (NaNj) in aqueous acetic acid to form a compound C3H5N3O in 71% yield Propanal (CH3CH2CH=0) when subjected to the same reaction conditions is recovered unchanged Suggest a structure for the product formed from acrolein and offer an explanation for the difference in reactivity between acrolein and propanal... 

The simplest a 3 unsaturated aldehyde acrolein is prepared by heating glycerol with an acid catalyst Suggest a mechanism for this reaction... 

Acrolein (H2C=CHCH=0) undergoes conjugate addition with sodium azide in aqueous solution to give N3CH2CH2CH=0 Propanal is not an a 3 unsaturated carbonyl compound and cannot undergo conjugate addition... 

Acrylaldehyde (not acrolein) Benzaldehyde Cinnamaldehyde 2-Furaldehyde (not furfural)... 

Ammonia, anhydrous Mercury, halogens, hypochlorites, chlorites, chlorine(I) oxide, hydrofluoric acid (anhydrous), hydrogen peroxide, chromium(VI) oxide, nitrogen dioxide, chromyl(VI) chloride, sulflnyl chloride, magnesium perchlorate, peroxodisul-fates, phosphorus pentoxide, acetaldehyde, ethylene oxide, acrolein, gold(III) chloride... 

Chlorosulfonic acid Saturated and unsaturated acids, acid anhydrides, nitriles, acrolein, alcohols, ammonia, esters, HCl, HF, ketones, hydrogen peroxide, metal powders, nitric acid, organic materials, water... 

Potassium hydride Air, chlorine, acetic acid, acrolein, acrylonitrile, maleic anhydride, nitroparaf-flns, A-nitrosomethylurea, tetrahydrofuran, water... 

Figure 5.1 Principal inertial axes of (a) hydrogen cyanide, (b) methyl iodide, (c) benzene, (d) methane, (e) sulphur hexafluoride, (f) formaldehyde, (g) s-lraws-acrolein and (h) pyrazine...

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