The Chemistry Of Salicylic Acid: Alcohol Or Phenol?

Salicylic acid is a colorless, bitter-tasting organic compound with the formula HOC6H4COOH. It is a plant hormone and has been used as a medication to treat warts, acne, psoriasis, and other skin conditions. Salicylic acid is also used in the preparation of ester derivatives, such as aspirin. In this process, salicylic acid reacts with either an acid or an alcohol. This raises the question of whether salicylic acid is classified as an alcohol or a phenol.

Salicylic acid is a phenolic phytohormone

Salicylic acid has medicinal properties, including analgesic and antipyretic characteristics, and is used in the treatment of warts, psoriasis, acne vulgaris, ringworm, dandruff, and ichthyosis. It is also an ingredient in many skincare products for treating various skin conditions. The major use of salicylic acid, however, is in the preparation of its ester derivatives. Salicylic acid contains both a hydroxyl (-OH) and a carboxyl (-CO2H) group, allowing it to react with either an acid or an alcohol. When heated, salicylic acid converts to phenyl salicylate, which is used in medicine as an antiseptic and antipyretic.

The synthesis of salicylic acid involves treating sodium phenolate (the sodium salt of phenol) with carbon dioxide at high pressure and temperature, followed by acidification with sulfuric acid to produce salicylic acid. Salicylic acid is also produced through the hydrolysis of aspirin (acetylsalicylic acid) or methyl salicylate (oil of wintergreen) using a strong acid or base. Methyl salicylate, an ester derived from the wintergreen plant, has a pleasant odour and is used for flavouring purposes. It can be taken internally or absorbed through the skin, making it useful in liniment preparations.

Salicylic acid plays a crucial role in plant defence against pathogens. It induces the production of pathogenesis-related proteins and other defensive metabolites, leading to systemic acquired resistance in plants. This defensive role has been demonstrated in experiments where the removal of salicylic acid resulted in a lack of typical high SA levels, SAR production, and expression of pathogenesis-related genes in systemic leaves. Salicylic acid's ability to mediate plant defence against pathogens highlights its significance in the field of plant science and agriculture.

Salicylic acid is derived from willow bark

Salicylic acid, a colourless or white, bitter-tasting solid, is an organic compound with the formula HOC6H4COOH. It is a plant hormone and a type of phenolic phytohormone. It is also a precursor to acetylsalicylic acid, commonly known as aspirin.

Salicylic acid is derived from the bark and leaves of the willow tree, also known as the Salix alba vulgaris or white willow tree. The name "salicylic" comes from "salix," the Latin word for willow. The willow tree's bark and leaves contain a substance called salicin, a type of alcohol that contains the compound β-glucoside. When consumed, the body breaks salicin down into glucose and salicyl alcohol, which is then converted into salicylic acid through a process called oxidation.

The use of salicylic acid as a pain reliever has a long history. The ancient Egyptians, Sumerians, and Hippocrates, as well as Celsus, Pliny the Elder, Dioscorides, and Galen, used willow bark and leaves to treat pain, fever, and inflammation. The Roman physician Celsus described the treatment of inflammation, characterised by redness, heat, pain, and swelling, with willow leaves. The Ebers Papyrus, an ancient Egyptian medical text, also mentions treating an inflamed wound with a concoction made from the leaves of the white willow tree. In 1763, Edward Stone conducted the first "clinical trial," successfully treating malarial fever with willow bark. In 1828, salicin was isolated from the willow tree and shown to have medicinal effects. It was further demonstrated that salicin could be converted into salicylic acid in the laboratory, resulting in a more potent drug.

Today, salicylic acid is commonly used in skincare products to treat various skin conditions, such as acne, psoriasis, dandruff, and warts. It is also used as a medication to remove the outermost layer of the skin in the treatment of warts, psoriasis, acne vulgaris, ringworm, dandruff, and ichthyosis. Salicylic acid is also found to have anti-inflammatory effects on inflammatory cells produced by COVID-19.

Salicylic acid is toxic in large amounts

Salicylic acid is a phenolic phytohormone, and is found in plants with roles in plant growth and development, photosynthesis, transpiration, and ion uptake and transport. It is also a plant hormone and has been listed by the EPA Toxic Substances Control Act (TSCA) Chemical Substance Inventory as an experimental teratogen. Salicylic acid is toxic in large amounts and can cause severe metabolic derangements that make treatment difficult. Salicylate toxicity is a medical emergency. Intentional ingestion or accidental overdose can lead to severe metabolic derangements, making treatment challenging. It can cause a variety of metabolic disorders, including hyperventilation, respiratory alkalosis, and metabolic acidosis.

Salicylic acid is often used in dermatological treatments due to its keratolytic, bacteriostatic, fungicidal, and photoprotective properties. Although rare, salicylic acid toxicity (salicylism) can occur from topical application. If high concentrations of salicylic ointment are used topically, high levels of salicylic acid can enter the blood, requiring hemodialysis to prevent further complications. Salicylates are widely available over-the-counter medications used for their analgesic, antipyretic, and anti-thrombotic properties.

Salicylate levels greater than 100 mg/dL are considered severe toxicity and can occur 12 to 24 hours after ingestion. They can cause damage to basement membranes, leading to cerebral and pulmonary edema. Patients may exhibit obtundation, seizures, and respiratory issues, including hyperventilation and hypoventilation, which can indicate impending respiratory failure. Additionally, hypotension, cardiac dysrhythmias, and cardiac arrest may occur in severe cases.

Salicylic acid is also known to cause digestive problems when consumed in high doses. These problems can include gastric irritation, bleeding, diarrhea, and even death. Salicylate poisoning can cause direct stimulation of the cerebral medulla, resulting in hyperventilation and respiratory alkalosis. As the body metabolizes salicylate, it causes an uncoupling of oxidative phosphorylation in the mitochondria, leading to increased lactate levels due to enhanced anaerobic metabolism. This, in turn, results in metabolic acidosis.

In summary, salicylic acid is toxic in large amounts and can lead to severe health issues and even death. It is important to be mindful of the potential risks associated with the use of salicylic acid, especially when used topically or consumed internally.

Salicylic acid is used to treat acne

Salicylic acid is a widely available, organic compound used to treat acne. It is considered safe overall, but it may cause skin irritation and dryness when first starting. Salicylic acid is a key ingredient in many skincare products, including cleansers, creams, lotions, liquids, gels, ointments, shampoos, wipes, pads, and patches.

Salicylic acid is a phenolic phytohormone, found in plants, and is involved in plant growth, development, photosynthesis, and transpiration. It is also a precursor to acetylsalicylic acid, commonly known as aspirin. Salicylic acid can be prepared in a laboratory by the hydrolysis of aspirin or methyl salicylate with a strong acid or base.

When used to treat acne, salicylic acid is applied topically to the affected areas of the skin. It works by helping the skin shed dead cells from the top layer, reducing redness and swelling, and unplugging blocked skin pores to allow pimples to shrink. It is recommended to gently wash the affected area with a mild cleanser, pat dry, and then apply a thin layer of the medication, gently rubbing it into the skin. It can be used several times a day, depending on the product and the condition being treated.

It is important to note that salicylic acid should not be used on broken, red, swollen, irritated, or infected skin. Before using salicylic acid, individuals should consult a doctor or dermatologist to ensure it is suitable for their skin and health condition, and to discuss any potential allergies or interactions with other medications.

Salicylic acid is used in the preparation of its ester derivatives

Salicylic acid is a phenolic phytohormone, a type of plant hormone involved in plant growth and development, photosynthesis, transpiration, and ion uptake and transport. It is also involved in endogenous signaling, mediating plant defense against pathogens. Salicylic acid occurs in plants as free salicylic acid and its carboxylated esters and phenolic glycosides.

The synthesis of acetylsalicylic acid (ASA or aspirin) involves the acetylation of salicylic acid with an acetyl group from acetic anhydride or acetyl chloride. ASA is a widely used non-steroidal anti-inflammatory drug (NSAID) and is the standard to which other NSAIDs are compared. Salicylic acid is also a precursor to methyl salicylate, which is used as a liniment to soothe joint and muscle pain.

Salicylic acid has been isolated from various natural sources, including the herb meadowsweet and the wintergreen plant. It has found applications in medicine, particularly in the treatment of skin conditions and as an anti-inflammatory agent.

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