Benzaldehyde Jump to navigationJump to search Benzaldehyde Skeletal (structural) formula Ball-and-stick model Names Preferred IUPAC name Benzaldehyde[1] Systematic IUPAC name Benzenecarbaldehyde Other names Benzenecarboxaldehyde Phenylmethanal Benzoic aldehyde Identifiers CAS Number 100-52-7 check 3D model (JSmol) Interactive image Interactive image ChEBI CHEBI:17169 check ChEMBL ChEMBL15972 check ChemSpider 235 check ECHA InfoCard 100.002.601 Edit this at Wikidata EC Number 202-860-4 KEGG D02314 check PubChem CID 240 RTECS number CU437500 UNII TA269SD04T check UN number 1990 CompTox Dashboard (EPA) DTXSID8039241 Edit this at Wikidata InChI[show] SMILES[show] Properties Chemical formula C7H6O Molar mass 106.124 g·mol−1 Appearance colorless liquid strongly refractive Odor almond-like Density 1.044 g/mL, liquid Melting point −57.12[2] °C (−70.82 °F; 216.03 K) Boiling point 178.1 °C (352.6 °F; 451.2 K) Solubility in water 6.95 g/L (25 °C)[3] log P 1.64[4] Magnetic susceptibility (χ) -60.78·10−6 cm3/mol Refractive index (nD) 1.5456 Viscosity 1.321 cP (25 °C) Thermochemistry Std enthalpy of formation (ΔfH⦵298) −36.8 kJ/mol Std enthalpy of combustion (ΔcH⦵298) −3525.1 kJ/mol Hazards Safety data sheet J. T. Baker GHS pictograms GHS07: Harmful GHS Signal word Warning GHS hazard statements H302 GHS precautionary statements P264, P270, P301+312, P330, P501 NFPA 704 (fire diamond) NFPA 704 four-colored diamond 220 Flash point 64 °C (147 °F; 337 K) Autoignition temperature 192 °C (378 °F; 465 K) Explosive limits 1.4–8.5% Lethal dose or concentration (LD, LC): LD50 (median dose) 1300 mg/kg (rat, oral) Related compounds Related compounds Benzyl alcohol Benzoic acid Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). check verify (what is check☒ ?) Infobox references Benzaldehyde (C6H5CHO) is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. It is a colorless liquid with a characteristic almond-like odor. The primary component of bitter almond oil, benzaldehyde can be extracted from a number of other natural sources.[5] Synthetic benzaldehyde is the flavoring agent in imitation almond extract, which is used to flavor cakes and other baked goods.[6] Contents 1 History 2 Production 3 Occurrence 4 Reactions 5 Uses 5.1 Niche uses 6 Safety 7 References 8 External links History Benzaldehyde was first extracted in 1803 by the French pharmacist Martrès. His experiments focused on elucidating the nature of amygdalin, the poisonous material found in bitter almonds, the fruit of Prunus dulcis.[7] Further work on the oil by Pierre Robiquet and Antoine Boutron-Charlard, two French chemists, produced benzaldehyde.[8] In 1832, Friedrich Wöhler and Justus von Liebig first synthesized benzaldehyde.[9] Production As of 1999, 7000 tonnes of synthetic and 100 tonnes of natural benzaldehyde were produced annually.[10] Liquid phase chlorination and oxidation of toluene are the main routes. Numerous other methods have been developed, such as the partial oxidation of benzyl alcohol, alkali hydrolysis of benzal chloride, and the carbonylation of benzene.[11] A significant quantity of natural benzaldehyde is produced from cinnamaldehyde obtained from cassia oil by the retro-aldol reaction:[10] the cinnamaldehyde is heated in an aqueous/alcoholic solution between 90 °C and 150 °C with a base (most commonly sodium carbonate or bicarbonate) for 5 to 80 hours,[12] followed by distillation of the formed benzaldehyde. This reaction also yields acetaldehyde. The natural status of benzaldehyde obtained in this way is controversial.[10] "Site-specific nuclear magnetic resonance spectroscopy", which evaluates 1H/2H isotope ratios, has been used to differentiate between naturally occurring and synthetic benzaldehyde.[13] Occurrence Benzaldehyde and similar chemicals occur naturally in many foods. Most of the benzaldehyde that people eat is from natural plant foods, such as almonds.[14] Almonds, apricots, apples, and cherry kernels contain significant amounts of amygdalin. This glycoside breaks up under enzyme catalysis into benzaldehyde, hydrogen cyanide and two equivalents of glucose. Amygdalin Amygdalin structure.svg 2 H 2O HCN Rightward reaction arrow with minor substrate(s) from top left and minor product(s) to top right benzaldehyde Benzaldehyde.png 2 × glucose 2 × Alpha-D-glucose-2D-skeletal-hexagon.png Benzaldehyde contributes to the scent of oyster mushrooms (Pleurotus ostreatus).[15] Reactions Benzaldehyde can be oxidized to benzoic acid; in fact "[B]enzaldehyde readily undergoes autoxidation to form benzoic acid on exposure to air at room temperature"[16] causing a common impurity in laboratory samples. Since the boiling point of benzoic acid is much higher than that of benzaldehyde, it may be purified by distillation. Benzyl alcohol can be formed from benzaldehyde by means of hydrogenation. Reaction of benzaldehyde with anhydrous sodium acetate and acetic anhydride yields cinnamic acid, while alcoholic potassium cyanide can be used to catalyze the condensation of benzaldehyde to benzoin. Benzaldehyde undergoes disproportionation upon treatment with concentrated alkali (Cannizzaro reaction): one molecule of the aldehyde is reduced to the benzyl alcohol and another molecule is simultaneously oxidized to benzoic acid. Cannizzaro reaction With diols, including many sugars, benzaldehyde condenses to form benzylidene acetals. Uses Benzaldehyde is commonly employed to confer almond flavor to foods and scented products. It is sometimes used in cosmetics products.[17] In industrial settings, benzaldehyde is used chiefly as a precursor to other organic compounds, ranging from pharmaceuticals to plastic additives. The aniline dye malachite green is prepared from benzaldehyde and dimethylaniline. Benzaldehyde is also a precursor to certain acridine dyes. Via aldol condensations, benzaldehyde is converted into derivatives of cinnamaldehyde and styrene. The synthesis of mandelic acid starts with the addition of hydrocyanic acid to benzaldehyde: mandelic acid synthesis The resulting cyanohydrin is hydrolysed to mandelic acid. (The scheme above depicts only one of the two formed enantiomers). Niche uses Benzaldehyde is used as a bee repellent.[18] A small amount of benzaldehyde solution is placed on a fume board near the honeycombs. The bees then move away from the honey combs to avoid the fumes.[19] The beekeeper can then remove the honey frames from the bee hive with less risk to both bees and beekeeper. Additionally, benzaldehyde is also used as a flavour chemical in JUUL e-cigarette pods, particularly the "Cool Mint", "Cool Cucumber", and "Fruit Medley" varieties. The concentration is relatively low, at ~1 μg/mL.[20] Safety As used in food, cosmetics, pharmaceuticals, and soap, benzaldehyde is "generally regarded as safe" (GRAS) by the US FDA[21] and FEMA.[14] This status was reaffirmed after a review in 2005.[14] It is accepted in the European Union as a flavoring agent.[17] Toxicology studies indicate that it is safe and non-carcinogenic in the concentrations used for foods and cosmetics,[17] and may even have anti-carcinogenic (anti-cancer) properties.[17] For a 70 kg human, the lethal dose is estimated at 50 mL.[11] An acceptable daily intake of 15 mg/day has been identified for benzaldehyde by the United States Environmental Protection Agency.[22] Benzaldehyde does not accumulate in human tissues.[17] It is metabolized and then excreted in urine.[17] Benzaldehyde Chemical Properties,Uses,Production description Benzaldehyde is an organic compound, and is synthetized by the way that the hydrogen of benzene is substituted by aldehyde. It is the most simple, and also the most commonly used industrial aromatic aldehyde. It is a colorless liquid at room temperature and has a special almond odor. Benzaldehyde is a compound that aldehyde is directly linked to the phenyl group, because it has a similar bitter almond flavor. Benzaldehyde widely exists in plant, especially in the Rosaceae plants. It is mainly in the form of glycosides in plant stem bark, leaves or seeds, such as amygdalin, bitter almond, cherry, laurel, peach. Benzaldehyde is naturally in bitter almond oil, patchouli oil, hyacinth oil, cananga oil. The compound is also in the nutlets and nuts, and exists in the form of Amygdalin, which is combination of glycosides. The chemical properties of Benzaldehyde is similar to that of aliphatic aldehydes, but It is also different. Benzaldehyde cannot reduce fehling reagent. When the reducing fat is used to reduce the benzaldehyde, the main products are benzene methanol, four substituted for the ortho-glycol and two-phenyl ethylene glycol. In the presence of potassium cyanide, two molecules of benzaldehyde form benzoin by acceptance the hydrogen atom. The substitution reaction in aromatic nucleus of benzaldehyde is mainly the meta-position product. For example, the main product is the m-nitrobenzaldehyde , when benzaldehyde is nitrated. benzaldehyde structure benzaldehyde structure Chemical Properties Benzaldehyde is the main, characteristic component of bitter almond oil. It occurs in many other essential oils and is a colorless liquid with a bitter almond odor. In the absence of inhibitors, benzaldehyde undergoes autoxidation to perbenzoic acid, which reacts with a second molecule of benzaldehyde to yield benzoic acid. Hydrogenation of benzaldehyde yields benzyl alcohol, and condensation with aliphatic aldehydes leads to additional fragrance substances or their unsaturated intermediates.Unsaturated araliphatic acids are obtained through the Perkin reaction, for example, the reaction with acetic anhydride to give cinnamic acid. Benzaldehyde is used in aroma compositions for its bitter almond odor. It is the starting material for a large number of araliphatic fragrance and flavor materials. Uses 1. Benzaldehyde is an important raw material for medicine, dyestuff, perfume and resin industry. It also can be used as solvent, plasticizer and low temperature lubricant. In essence, it is mainly used for the deployment of food flavor. A small amount of benzaldehyde is daily use in flavor and flavor of tobacco. In spite of being widely used as commercial food condiment and industrial solvents, the main use of benzyl alcohol is still used to synthesize a variety of other compounds from pharmaceuticals to plastic additives. Benzyl alcohol is an important intermediate product in the production of perfumes, spices, and some aniline dyes. Mandelic acid was synthesized by benzaldehyde as the starting reagent: With the first hydrocyanic acid reacts with benzaldehyde, then mandelonitrile hydrolyzed to Racemic mandelic acid. Glacialist LaChepelle and Stillman reported Ice crystallization is inhibited by benzaldehyde and aldehydes ice in 1966, so as to prevent the thick frost formation (Depth Hoar). This process can prevent snowslide caused by the instability of the snow cover. However, this compound has not been used extensively, because of the destruction of vegetation and polluted water sources. 2.It is mainly used for the preparation of flavors, such as almond, cherry, peach, nuts, etc., the amount is up to 40%. As aromatizing agent canned cherry syrup, adding amount is sugar 3mL/kg. 3. Pharmaceutical, dyestuff, spice intermediates. For the production of oxygen based benzene formaldehyde, lauric acid, lauric aldehyde, malachite, benzyl benzoate, benzyl aniline and benzylidene acetone etc.. Used to tune the soap flavor, edible essence, etc. 4. As the head of the special aroma, it is used trace formula for fragrance, such as lilac, white, violet, jasmine, acacia, sunflower, sweet plum, orange flower, Tofu pudding etc.. Also it is used in soap. Also it can be used as edible spices for almond, coconut cream, berries, cherries, apricots, peaches, plums, walnuts, and vanilla bean, spicy flavor. Wine with flavors such as rum, brandy, etc. 5. Benzaldehyde is an intermediate of herbicide resistance, plant growth regulator, and anti-amine. 6. Used as a reagent for the determination of ozone, phenol, alkaloid and methylene. Used in the preparation of spices. Production Benzaldehyde can be prepared by a variety of ways. Obtained from natural essential oils by fractionation. Ozone oxidation and thiourea reduction reaction of natural cinnamon oil (containing cinnamaldehyde constituent 80% or more) Catalytic oxidation of Toluene Hydrolyze dichloromethane under alkaline conditions. reactions Benzaldehyde can be slowly oxidized to benzoic acid in air, so a small amount of hydroquinone is often added to prevent its oxidation. There is no α-H atom in the benzaldehyde molecule. Disproportionation reaction(Cannizarro reaction) may occur under the action of concentrated alkali: Heating benzaldehyde in the presence of catalyst of cyanide ion, it will occur bimolecular condensation: Chemical Properties Benzaldehyde is a colorless to yellow, oily liquid with an odor of bitter almonds. Benzaldehyde is commercially available in two grades: (i) pure benzaldehyde and (ii) and double-distilled benzaldehyde. The latter has applications in the pharmaceutical, perfume, and fl avor industries. Benzaldehyde may contain trace amounts of chlorine, water, benzoic acid, benzyl chloride, benzyl alcohol, and/or nitrobenzene. Benzaldehyde is ignited relatively easily on contact with hot surfaces. This has been attributed to the property of very low auto-ignition temperature. Benzaldehyde also undergoes autoxidation in air and is liable to self-heat. Benzaldehyde exists in nature, occurring in combined and uncombined forms in many plants. Benzaldehyde is also the main constituent of the essential oils obtained by pressing the kernels of peaches, cherries, apricots, and other fruits. Benzaldehyde is released into the environment in emissions from combustion processes, such as gasoline and diesel engines, incinerators, and wood burning. It is formed in the atmosphere through photochemical oxidation of toluene and other aromatic hydrocarbons. Benzaldehyde is corrosive to gray and ductile cast iron (10% solution), and all concentrations of lead. However, pure benzaldehyde is not corrosive to cast iron. Benzaldehyde does not attack most of the common metals, like stainless steels, aluminum, aluminum bronze, nickel and nickel-base alloys, bronze, naval brass, tantalum, titanium, and zirconium. On decomposition, benzaldehyde releases peroxybenzoic acid and benzoic acidBenzaldehyde is used in perfumes, soaps, foods, drinks, and other products; as a solvent for oils, resins, some cellulose ethers, cellulose acetate, and cellulose nitrate. The uses of benzaldehyde in industries are extensive. For instance, in the production of derivatives that are employed in the perfume and fl avor industries, like cinnamaldehyde, cinnamyl alcohol, cinnamic acid, benzylacetone, and benzyl benzoate, in the production of triphenylmethane dyes and the acridine dye, benzofl avin; as an intermediate in the pharmaceutical industry, for instance, to make chloramphenicol, ephedrin, and ampicillin, as an intermediate to make benzoin, benzylamine, benzyl alcohol, mandelic acid, and 4-phenyl-3-buten-2-one (benzylideneacetone), in photochemistry, as a corrosion inhibitor and dyeing auxiliary, in the electroplating industry, and in the production of agricultural chemicals Occurrence Present as cyanuric glucoside (amygdalin) in bitter almond, peach, apricot kernel and other Prunus species; amygdalin is also present in various parts of the following plants: Sambucus nigra, Chrysophyllum arlen, Anacyclus officinarnm, Anacyclus pedunculatus, Davallia brasiliensis, Lacuma deliciosa, Lacuma multiflora and others; free benzaldehyde has been reported found in several essential oils: hyacinth, citronella, orris, cinnamon, sassafras, labdanum and patchouli. Reported found in strawberry jam, leek (raw) (Allium porrum L.), crispbread, Camembert, Gruyere de Comte, provolone cheeses, black tea, salted and pickled plum, cooked trassi, Bantu beer, red sage (Texas sage) (S. coccinea Juss. Ex Murr.), arrack, scallop, hog plum (Spondias mombins L.), chekur (Alpinia sessilis Kon. = Kaemferia galanga) and other natural sources. Uses Benzaldehyde is used as an intermediatein the production of flavoring chemicals,such as cinnamaldehyde, cinnamalalcohol,and amyl- and hexylcinnamaldehyde for perfume,soap, and food flavor; synthetic penicillin,ampicillin, and ephedrine; and as araw material for the herbicide Avenge. Itoccurs in nature in the seeds of almonds,apricots, cherries, and peaches. It occurs intrace amounts in corn oil. Uses Manufacture of dyes, perfumery, cinnamic and mandelic acids, as solvent; in flavors. Uses Benzaldehyde is a flavoring agent which is liquid and colorless, and has an almond-like odor. it has a hot (burning) taste. it is oxidized to benzoic acid when exposed to air and deteriorates under light. it is miscible in volatile oils, fixed oils, ether, and alcohol; it is spar- ingly soluble in water. it is obtained by chemical synthesis and by natural occurrence in oils of bitter almond, peach, and apricot kernel. it is also termed benzoic aldehyde. Definition A yellow organic oil with a distinct almondlike odor. Benzenecarbaldehyde undergoes the reactions characteristic of aldehydes and may be synthesized in the laboratory by the usual methods of aldehyde synthesis. It is used as a food flavoring and in the manufacture of dyes and antibiotics, and can be readily manufactured by the chlorination of methylbenzene and the subsequent hydrolysis of (dichloromethyl) benzene: C6H5CH3 + Cl2 →C6H5CHCl2 C6H5CHCl2 + 2H2O →C6H5CH(OH)2+ 2HCl C6H5CH(OH)2 →C6H5CHO + H2O. Preparation Benzaldehyde is prepared by hydrolysis of benzal chloride, for example, in acidic media in the presence of a catalyst such as ferric chloride or in alkaline media with aqueous sodium carbonate. Part of the commercially available benzaldehyde originates from a technical process for phenol. In this process, benzaldehyde is a by-product in the oxidation, in air, of toluene to benzoic acid. Reactions Benzaldehyde reacts with many chemicals in a marked manner: (1) with ammonio-silver nitrate (“Tollen’s solution”) to form metallic silver, either as a black precipitate or as an adherent mirror film on glass (but does not reduce alkaline cupric solution, “Fehling’s solution”); (2) with rosaniline (fuchsine, magenta) that has been decolorized by sulfurous acid (“Schiff’s solution”), restoring the pink color of rosaniline; (3) with NaOH solution, yielding benzyl alcohol and sodium benzoate; (4) with NH4OH, yielding tribenzaldeamine (hydrobenzamide, (C6H5CH)3N2), white solid, mp 101 °C, (5) with aniline, yielding benzylideneaniline (“Schiff’s base” C6H5CH:NC6H5); (6) with sodium cyanide in alcohol, yielding benzoin C6H5·CHOHCOC6H5, white solid, mp 133 °C; (7) with hydroxylamine hydrochloride, yielding benzaldoximes C6H5CH:NOH, white solids, antioxime, mp 35 °C, syn-oxime, mp 130 °C; (8) with phenylhydrazine, yields benzaldehyde phenylhydrazone C6H5CH:NNHC6H5, pink solid, mp 156 °C; (9) with concentrated HNO3, yields metanitrobenzaldehyde NO2·C6H4CHO, white solid, mp 58 °C; (10) with concentrated H2SO4 yields metabenzaldehyde sulfonic acid C6H4CHO (SO3H)2, (11) with anhydrous sodium acetate and acetic anhydride at 180 °C, yielding sodium benzoate C6H5CHOONa (12) with sodium hydrogen sulfite, forming benzaldehyde sodium bisulfite C6H5CHOHSO3Na, a white solid, from which benzaldehyde is readily recoverable by treatment with sodium carbonate solution; (13) with acetaldehyde made slightly alkaline with NaOH, yielding cinnamic aldehyde C6H5CH:CHCHO, (14) with phosphorus pentachloride, yielding benzylidine chloride C6H5CHCl2. Aroma threshold values Detection: 100 ppb to 4.6 ppm; Recognition: 330 ppb to 4.1 ppm. Taste threshold values Taste characteristics at 50 ppm: sweet, oily, almond, cherry, nutty and woody Synthesis Reference(s) Chemical and Pharmaceutical Bulletin, 12, p. 403, 1964 The Journal of Organic Chemistry, 58, p. 4732, 1993 DOI: 10.1021/jo00069a043 Synthetic Communications, 16, p. 43, 1986 DOI: 10.1080/00397918608057686 General Description A clear colorless to yellow liquid with a bitter almond odor. Flash point near 145°F. More denser than water and insoluble in water. Hence sinks in water. Vapors are heavier than air. The primary hazard is to the environment. Immediate steps should be taken to limit spread to the environment. Easily penetrates the soil to contaminate groundwater and nearby waterways. Used in flavoring and perfume making. Air & Water Reactions Oxidizes in air to form benzoic acid, which is moderately toxic by ingestion. Insoluble in water. Reactivity Profile A nontoxic, combustible liquid, reacts with oxidizing reagents. Benzaldehyde must be blanketed with an inert gas at all times since Benzaldehyde is oxidized readily by air to benzoic acid [Kirk-Othmer, 3rd ed., Vol. 3, 1978, p. 736]. In contact with strong acids or bases Benzaldehyde will undergo an exothermic condensation reaction [Sax, 9th ed., 1996, p. 327]. A violent reaction was observed on contact with peroxyacids (peroxyformic acid) [DiAns, J. et al., Ber., 1915, 48, p. 1136]. An explosion occurred when pyrrolidine, Benzaldehyde, and propionic acid were heated to form porphyrins. Hazard Highly toxic. Health Hazard Benzaldehyde exhibited low to moderate toxicityin test animals, the poisoning effectdepending on dosage. Ingestion of 50–60 mLmay be fatal to humans. Oral intake of a largedose can cause tremor, gastrointestinal pain,and kidney damage. Animal experimentsindicated that ingestion of this compoundby guinea pigs caused tremor, bleeding fromsmall intestine, and an increase in urine volume;in rats, ingestion resulted in somnolenceand coma. LD50 value, oral (guinea pigs): 1000 mg/kg LD50 value, oral (rats): 1300 mg/kg A 500-mg amount for a 24-hour periodresulted in moderate skin irritation in rabbits.Because of its low toxicity, high boilingpoint, and low vapor pressure, the healthhazard to humans from exposure to benzaldehydeis very low. Fire Hazard HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. Vapors may form explosive mixtures with air. Vapors may travel to source of ignition and flash back. Most vapors are heavier than air. They will spread along ground and collect in low or confined areas (sewers, basements, tanks). Vapor explosion hazard indoors, outdoors or in sewers. Runoff to sewer may create fire or explosion hazard. Containers may explode when heated. Many liquids are lighter than water. Chemical Reactivity Reactivity with Water: No reaction; Reactivity with Common Materials: No reactions; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Not pertinent; Polymerization: Not pertinent; Inhibitor of Polymerization: Not pertinent. Pharmacology Benzaldehyde significantly inhibited peptic activity in artificial gastric juice in vitro (20-45% inhibition) and in vivo to the extent of 87% in normal healthy persons and ulcer patients (Kleeberg, 1959). As a freshly prepared 1:500 solution, it exerted a marked antispasmodic effect, relaxing the tonus and inhibiting contractions of various isolated smooth muscles of dog, cat, rat, rabbit, mouse, guinea-pig, pig and frog and of a few human tissues. Injected into rabbits and other animals it produced a marked relaxation of the intestines and urinary bladder and marked vasodilation of the splanchnic vessel. Injection of 4 ml of a 5% solution iv into a cat caused a fall in blood pressure and slowing of respiration. In dogs, 1 ml injected iv or sc or 2 ml/kg given orally produced only a slight slowing of respiration. Injection of larger doses iv produced only a drop in blood pressure, slight slowing of respiration and inhibition of intestinal contractions, with vasodilation of the splanchnic vessel. In rabbits, iv injection of 20 ml of a 0-2% solution did not produce dangerous results. Large injected doses of benzaldehyde exert their mosjt important toxic effects on the medulla, with slowing or paralysis of respiration. In the intact animal, the heart is very little affected; but benzaldehyde acts as a muscular depressant on isolated frog heart (Macht, 1922). Treatment of isolated rat striated muscle for 1-5 min with 30 mM-benzaldehyde increased the rate of propagation of contractures and the rate of structural breakdown of injured striated muscle fibres. After more prolonged application (for 30 min), the rapid propagation of contracture continued but the structural breakdown was inhibited (Busing, 1972). Benzaldehyde possessed definite local anaesthetic properties in the sciatic nerves of cats, dogs and frogs, in the eyes of rabbits and dogs (accompanied by irritation) and in the skin of frogs, but was considered unsuitable for practical use because of its rapid oxidation to benzoic acid (Macht, 1922). In a study of the toxic effects of cherry laurel water on mice and on isolated rat intestine, benzaldehyde was found to aid in the detoxication of HCN by the formation of C6H5?CH(OH)?CN (Lanza & Conte, 1964). Benzaldehyde did not act as a cross-linking (tanning) agent for corium and aorta, since in a 015 M solution it did not increase the observed in vitro hydrothermal shrinkage temperatures of goat skin and human, bovine and canine aortae (Milch, 1965). The intestinal absorption-rate coefficients of benzaldehyde and related compounds were determined by perfusion of aqueous solutions through the small intestines of anaesthetized rats (Nogami, Hanano & Yamada, 1968). No changes in gastric motor patterns, including gastric motility, were observed in rats after inhalation of "toxic levels" (not specified) of benzaldehyde from a liquid sample placed in a test chamber using recirculated air, or from a saturated paper applied to the trachea (Roth & Tansy, 1972). Benzaldehyde in a concentration of 0-1 mmol/litre caused a 16% depression of the frequency of electric-organ discharge in the mormyrid electric fish Gnathonemus moori (Walsh & Schopp, 1966). Safety Profile Poison by ingestion and intraperitoneal routes. Moderately toxic by subcutaneous route. An allergen. Acts as a feeble local anesthetic. Local contact may cause contact dermatitis. Causes central nervous system depression in small doses and convulsions in larger doses. A skin irritant. Questionable carcinogen with experimental tumorigenic data. Mutation data reported. Combustible liquid. To fight fire, use water (may be used as a blanket), alcohol, foam, dry chemical. A strong reducing agent. Reacts violently with peroxyformic acid and other oxidizers. See also ALDEHYDES. Chemical Synthesis Natural benzaldehyde is obtained by extraction and subsequent fractional distillation from botanical sources; synthetically, from benzyl chloride and lime or by oxidation of toluene Potential Exposure In manufacture of perfumes, dyes, and cinnamic acid; as solvent; in flavors. Metabolism Benzaldehyde was among 300 volatile constituents detected in the urine of ten adults . It is commonly converted to hippuric acid in vivo. In the rabbit and dog, hippuric acid appears to be the only metabolite there being practically no formation of benzoyl glucuronide. The conversion of benzaldehyde to benzoic acid in the rabbit follows first-order reaction kinetics storage Benzaldehyde should be kept stored in a tightly closed container and protected against physical damage. Storage of the chemical substance outside or in a detached area is preferred, whereas inside storage should be in a standard flammable liquids storage room or cabinet. Benzaldehyde should be kept separated from oxidizing materials. Also, storage and use areas should be no smoking areas. Containers of this material may be hazardous when empty since they retain product residues (vapors, liquid); observe all warnings and precautions listed for the product Shipping UN1990 Benzaldehyde, Hazard class: 9; Labels: 9—Miscellaneous hazardous material. Purification Methods To diminish its rate of oxidation, benzaldehyde usually contains additives such as hydroquinone or catechol. It can be purified via its bisulfite addition compound but usually distillation (under nitrogen at reduced pressure) is sufficient. Prior to distillation it is washed with NaOH or 10% Na2CO3 (until no more CO2 is evolved), then with saturated Na2SO3 and H2O, followed by drying with CaSO4, MgSO4 or CaCl2. [Beilstein 7 IV 505.] Incompatibilities The substance reacts with air, forming explosive peroxides. Reacts violently with performic acid, oxidants, aluminum, iron, bases, and phenol, causing fire and explosion hazard. May self-ignite if absorbed in combustible material with large surface area, or otherwise dispersed over large areas. Reacts with rust, amines, alkalies, strong bases, reducing agents such as hydrideds and active metals. Waste Disposal Incineration; add combustible solvent and spray into incinerator with afterburner. Precautions Workers should be careful when using benzaldehyde because there is a risk of spontaneous combustion. It may ignite spontaneously if it is absorbed onto rags, cleaning cloths, clothing, sawdust, diatomaceous earth (kieselguhr), activated charcoal, or other materials with large surface areas in workplaces. Workers should avoid handling the chemical substance and should not cut, puncture, or weld on or near the container. Exposure of benzaldehyde to air, light, heat, hot surfaces such as hot pipes, sparks, open flames, and other ignition sources should be avoided. Workers should wear proper personal protective clothing and equipment Benzaldehyde Preparation Products And Raw materials