Phenylacetaldehyde

Phenylacetaldehyde is an organic compound which can be naturally found in buckwheat, flowers, and communication pheromones from various insect orders. It is commonly used for the preparation of fragrance as well as flavors, and applied in flavored cigarettes and beverages because of its honey-like sweet character. It is also applied in the synthesis of polymers, such as polyesters, as a rate controlling additive in polymerization reactions and used in the preparation of more complex chemicals like resmethrin, where it acts as a building block.

Phenylacetaldehyde has a harsh, green odor reminiscent of hyacinth on dilution. It has an unpleasant, pungent, bitter flavor, turning sweet and fruit-like at low levels. Since it readily undergoes oxidation and polymerizes, it must be stabilized by addition of antioxidants and by dilution with, for example, diethyl phthalate before use in compositions.

Identified among the constituents of several essential oils: neroli, Citrus sinensis leaves, other citrus species (flowers and leaves), narcissus, magnolia, lily, rose and tea. It is reported found in over 170 natural products including apricot, sour cherry, cooked apple, peach, fresh blackberry, crispbread, other types of bread, green tea, unprocessed rice, lemon balm, red sage, black currant, bilberry, cranberry, other berries, grapes, raisins, melon, papaya, guava fruit, pineapple, asparagus, celery leaves, carrot, parsley, peas, bell pepper, sweet pepper, peach, cabbage, peppermint oil, Scotch spearmint oil, mustard, vinegar, onion, cooked potato, tomato, cinnamon bark, cassia leaf, ginger, many cheeses, milk, yogurt, boiled egg, cooked and cured meats, beer, cognac, grape wines, cocoa, coffee, tea, roasted filbert, roasted peanut, soybean, pecans, cauliflower, broccoli, honey, avocado, passion fruit, beans, mushrooms, trassi, mango, tamarind, rice, licorice, buckwheat, lovage root, pumpkin, sweet potato, cassava, corn oil, malt, wort, dried bonito, loquat, pawpaw, maté, sweet grass oil, orange peel oil, grapefruit juice, endive, clam and Chinese quince.

Phenylacetaldehyde is used for the preparation of fragrances and polymers like polyesters, which find application as a rate controlling additive in polymerization reactions. It is an active component of fragrances and floral scent due to its honey-like sweet character and finds application in flavored cigarettes and beverages. It is an insect attractant and utilized in blacklight trap for pests. It is also used as a building block in the synthesis of more complex chemicals, such as resmethrin. Furthermore, it is used in association with acetic anhydride and allyltrimethylsilane in three-component coupling process catalyzed by LiBF4 providing homoallylic acetates.

ChEBI: Phenylacetaldehyde is an aldehyde that consists of acetaldehyde bearing a methyl substituent; the parent member of the phenylacetaldehyde class of compounds. It has a role as a human metabolite, a Saccharomyces cerevisiae metabolite, an Escherichia coli metabolite and a mouse metabolite. It is an alpha-CH2-containing aldehyde and a member of phenylacetaldehydes.

Detection: 4 ppb. Aroma characteristics at 1.0%: sweet, floral honey, rosy and slightly powdery with a fermented note, cocoa and tobacco with a yellow tropical fruity nuance.

Taste characteristics at 5 ppm: floral and honey-like with a sweet floral, fruity, tobacco, with a yellow tropical fruity waxy nuance.

Journal of the American Chemical Society, 99, p. 4536, 1977 DOI: 10.1021/ja00455a071
Tetrahedron Letters, 29, p. 1471, 1988 DOI: 10.1016/S0040-4039(00)80328-7

Phenylacetaldehyde is an important aroma volatile found in tomato and roses. It has also been identified in potato, roasted cocoa beans and honey. Phenylacetaldehyde is also a potent moth attractant.

Phenylacetaldehyde is an insect attractant and can be used in blacklight trap for pests. It is constituent of floral scent. It is an intermediate in a variety of biochemical pathways.

Moderately toxic by ingestion. Human skin irritant. Combustible liquid. When heated to decomposition it emits acrid smoke and irritating fumes. See also ALDEHYDES.

The most important method industrially is the isomerization of styrene oxide. Ion-exchange resins, catalysis by chromium trioxide–tungsten trioxide on graphite or silicon dioxide–aluminum trioxide, and thermolysis are recommended for the rearrangement. Phenylacetaldehyde can also be synthesized by the direct oxidation of styrene in the presence of palladium salts and copper(II) chloride in aqueous solutions of glycol ethers. Other possibilities include the catalytic dehydrogenation of 2-phenylethanol on silver or gold catalysts, the hydroformylation of benzyl halides in the presence of dicobalt octacarbonyl and sodium carbonate in acetonitrile, and the Darzens glycide ester synthesis from benzaldehyde and alkyl chloroacetates.

Phenylacetaldehyde can be synthesized by Darzen glycidic ester synthesis from benzaldehyde; readily oxidizable to phenyl acetic acid.

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