material physics
CASR number: 107-02-8
Molecular formula: C 3 H 4 O
Alias: Acrylic aldehyde, aqualin, Magnacide
Melting point: -88°C
Boiling point: 52.5°C
Proportion: 0.843
Vapor pressure: 29.3 - 36.5 kPa at 20°C
Flash point: -18℃
history
In 1839, Swedish chemist Jöns Jacob Berzelius first named acrolein and characterized it as an aldehyde. He had been studying it as a thermal degradation product of glycerol, a material used to make soap. The name is an abbreviation of "acrid" (referring to its pungent smell) and "oleum" (referring to its oily consistency). In the 20th century, acrolein became an important intermediate in the industrial production of acrylic acid and acrylic plastics.
make
Acrolein is produced industrially through the oxidation of propylene. This process uses air as the oxygen source and requires metal oxides as heterogeneous catalysts:
- CH 3 CH=CH 2 + O 2 → CH 2 =CHCHO + H 2 O
North America, Europe and Japan produce approximately 500,000 tons of acrolein in this way each year. Furthermore, all acrylic acid is produced through the transient formation of acrolein.
Propane is a promising but challenging feedstock for the synthesis of acrolein. The main challenge is actually over-oxidation of this acid.
When glycerin (also known as glycerol) is heated to 280°C, it decomposes into acrolein:
- (CH 2 OH) 2 CHOH → CH 2 =CHCHO + 2 H 2 O
This route is attractive when glycerol is co-generated during the production of biodiesel from vegetable oils or animal fats. Glycerol dehydration has been demonstrated but has not yet been proven to be competitive with the petrochemical route.
niche or laboratory approach
The original industrial route to acrolein developed by Degussa involved the condensation of formaldehyde and acetaldehyde:
- HCHO + CH 3 CHO → CH 2 =CHCHO + H 2 O
Acrolein can also be produced on a laboratory scale by the action of potassium bisulfate and glycerin.
reaction
Acrolein is a relatively electrophilic and reactive compound and therefore highly toxic. It is a good Michael acceptor and therefore can react usefully with thiols. It readily forms acetals, one of the prominent acetals is a spiro ring derived from pentaerythritol, diallylenepentaerythritol. Acrolein participates in many Diels-Alder reactions and even itself. Via the Diels-Alder reaction, it is a precursor to several commercial fragrances, including lyraldehyde, norbornene-2-carbaldehyde and myrac aldehyde. The monomer 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate is also produced from acrolein via a tetrahydrobenzaldehyde intermediate.
use
military use
Acrolein was used in warfare for its irritating and foaming properties. During World War I, the French used this chemical called Papite in grenades and artillery shells.
Fungicide
Acrolein is primarily used as a contact herbicide to control submerged and floating weeds and algae in irrigation canals. It is used at 10 ppm in irrigation and recycled water. In the oil and gas industry, it is used as a biocide in drilling water and as a scavenger for hydrogen sulfide and mercaptans.
Chemical precursors
Taking advantage of acrolein's dual functionality, many useful compounds are made from acrolein. The amino acid methionine is produced by adding methylmercaptan followed by Strecker synthesis. Acrolein condenses with acetaldehyde and amines to form methylpyridine. It is also an intermediate in Skraup's synthesis of quinoline.
Acrolein polymerizes in the presence of oxygen and in water with concentrations above 22%. The color and texture of the polymer depend on conditions. The polymer is a clear yellow solid. In water, it forms a hard, porous plastic.
Acrolein has been used as a fixative in the preparation of biological specimens for electron microscopy.
health risks
Acrolein is toxic and highly irritating to skin, eyes and nasal passages. The main metabolic pathway of acrolein is alkylation of glutathione. The World Health Organization recommends a "tolerable oral intake of acrolein" of 7.5 micrograms per kilogram of body weight per day. Although French fries (and other fried foods) contain acrolein, the amount is only a few micrograms per kilogram. For occupational exposure to acrolein, the U.S. Occupational Safety and Health Administration has set a permissible exposure limit of 0.1 ppm (0.25 mg/m 3 ) for an eight-hour time-weighted average. Acrolein acts in an immunosuppressive manner and may promote the growth of regulatory cells, thereby preventing the development of allergies but also increasing the risk of cancer.
Acrolein is extremely or highly toxic to a variety of freshwater fish, aquatic invertebrates, algae, and aquatic plants. It is used as a herbicide in aquatic systems such as irrigation channels due to its toxicity to aquatic plants and algae and its relatively rapid dissipation from water. There is no evidence that it accumulates in living tissue, although studies in animals at high, long-term, repeated doses have shown that acrolein can cause systemic effects on many systems, including the respiratory, reproductive, nervous, and hematological systems.
Acrolein can enter the environment through burning trees, cigarettes or fuel. It may be found in air, water or land. Acrolein can also enter the environment from industrial spills or hazardous waste sites. Water treated with acrolein for weed control is retained for a sufficient time to allow the acrolein to dissipate before being released into the environment.
cigarette smoke
There is a link between acrolein gas in cigarette smoke and lung cancer risk. Acrolein is one of the seven toxic substances in cigarette smoke most associated with respiratory carcinogenesis. The mechanism of action of acrolein appears to involve induction of increased reactive oxygen species and DNA damage associated with oxidative stress.
In terms of the "non-carcinogenic health quotient" of components in cigarette smoke, acrolein dominates, and its contribution is 40 times higher than the next component, hydrogen cyanide. The amount of acrolein in cigarette smoke depends on the type of cigarette and the added glycerin, and can range up to 220 micrograms per cigarette. Importantly, although the concentration of components in mainstream smoke can be reduced through filters, this has no significant effect on the components of sidestream smoke where acrolein normally resides and is inhaled through passive smoking. Normally used e-cigarettes produce only "negligible" levels of acrolein.
chemotherapy metabolites
Treatment with cyclophosphamide and ifosfamide results in the production of acrolein. Acrolein produced during cyclophosphamide treatment can accumulate in the bladder and, if left untreated, may lead to hemorrhagic cystitis.
endogenous production
Acrolein is a component of Reuteria sp. Intestinal microbes can produce reuterin when glycerol is present. Microbially produced reuterin is a potential source of acrolein.
Acrolein and food
Optimizing food thermal processing to reduce acrolein production
Thermal processing of food is an important source of acrolein in the atmosphere. Acrolein is produced through various pathways during thermal processing of food and is widely distributed in fried foods, baked foods, overheated vegetable oils, alcoholic beverages, and foods rich in lipids and carbohydrates. Epidemiological research results show that the high incidence of lung cancer in Chinese women is related to acrolein produced by the raw materials of wok at high temperatures. Therefore, people are exposed to acrolein through diet, and the combination of artificial and optimized diet may be an important way to effectively control the intake of acrolein in human food, which is of great significance to maintaining human health. Research shows that excessive temperature is an important factor in the formation of acrolein in hot grease. The researchers observed that acrolein levels in fats and oils increased with time and temperature. Therefore, optimizing the heat treatment process of foods in the diet, such as reducing the production of acrolein by lowering the temperature during cooking, can alleviate health problems caused by acrolein ingestion in humans. Of course, while reducing the generation of acrolein during food thermal processing, attention should also be paid to maintaining and improving the flavor and color of food.
Explore more natural products as food additives to control acrolein levels
Many studies have found that some natural product extracts, such as amino acids, polyphenols, etc., can also control the formation of acrolein to a certain extent as food additives. Amino acids abundant in food can react with acrolein under mild conditions to form adducts, thereby reducing the production of acrolein in thermally processed foods. Free amino acids in food, such as alanine and serine, not only effectively remove acrolein under physiological conditions, but also can quickly and effectively remove acrolein at high temperatures such as 160°C. In addition, L-alanine has been included in the Chinese national standard (GB 2760-2014) and is used as a flavor enhancer in China. In recent years, the good antioxidant activity of polyphenols has made them widely used in the production of various baked goods, with the purpose of reducing the content of food-borne toxins and enhancing their functional properties. Studies have found that myricetin can scavenge acrolein produced during cookie making, suggesting that adding flavonoids to baked goods may inhibit the production of acrolein during food processing. The catechins in matcha powder can significantly inhibit the accumulation of reactive carbonyl species (RCS) during the baking process, and its thermal stability demonstrates the ability of matcha as a food additive. Therefore, adding matcha powder to cake dough can not only increase the flavor of the cake, but also reduce the content of RCS compounds such as acrolein.
In addition, amino acids and polyphenols need to pay attention to the following issues as food additives:
- The bioavailability of amino acids and polyphenols in the human body and the risk of their accumulation;
- The influence of the thermal degradation characteristics of polyphenols on their acrolein removal effect;
- The safety of adducts formed by the reaction of amino acids, polyphenols and acrolein and their exposure in different foods;
- Interactions of amino acids and polyphenols with other food components;
- Absorption and metabolism of adducts in the human body, etc.
Therefore, it is necessary to fully evaluate the consequences of adding amino acids and polyphenols to foods.
In summary, in the future food industry, it is an important development to discover more natural products that can be used to control food-borne poisons or are rich in antioxidant activity as additives that can not only increase the flavor of food but also serve as additives. direction. It can also improve the functional properties of food, control the content of food-borne toxic substances, and produce food that is more in line with human health.
