Carboxylic Acid: Examples & Uses

Carboxylic acid

Carbon is one of the most crucial elements for any life form to exist on planet earth, and it has a specialized field of study associated with it called organic chemistry. Although hydrocarbons form the backbone of organic chemistry, other factors such as bonding and functional groups contribute to the distinctive properties that several carbon compounds exhibit. A carboxyl group (COOH) is a functional group consisting of a carbonyl group (C=O) with a hydroxyl group (O-H) attached to the same carbon atom. The general formula of a carboxylic acid is R−COOH, with R referring to the alkyl, alkenyl, aryl, or other groups. The acidic nature of carboxylic acids comes from the hydrogen in the -COOH group, which dissociates from the rest of the compound, making it a proton donor. Although carboxylic acids are weaker acids than mineral acids, the acidity of a carboxylic acid is higher than alcohols and even phenols. This happens because the carboxylate ion formed on dissociation is stronger than anions formed in other cases.  Carboxylic acids do not dimerize in water but form hydrogen bonds with water and are considered polar and due to the presence of hydroxyl in the carboxyl group. Due to the presence of both hydroxyl and the carbonyl groups in the molecule, the carboxylic acids can exhibit hydrogen bonding with themselves, leading to increased stabilization of the compounds and show elevated boiling points. In non-polar media, carboxylic acids exist as dimeric pairs due to their capacity to form hydrogen bonds. Carboxylic acids occur widely in nature, often combined with alcohols or other functional groups, as in fats, oils, and waxes. Let’s take a look at few examples of carboxylic acids and their uses in our daily life.

Acetic Acid.

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Acetic acid, also known as ethanoic acid, is an important carboxylic acid with the chemical formula {CH}_{3}{COOH}, a distinctive pungent odor, and a sour flavor. Acetic acid has a variety of uses, including as raw material and solvent for the production of other chemicals. It can be found in the kitchen in vinegar; however, the acetic acid present in the vinegar is solute (5-8% as a volume) and not a solvent. Liquid acetic acid is a hydrophilic polar protic solvent just like water and ethanol. It does not only dissolves ionic salts and sugars, but also non-polar compounds such as oils as well as polar solutes. Vinegar is commonly used in the home for cleaning, laundry, cooking, and a variety of other tasks. To combat bacterial and fungal growth, farmers spray acetic acid on cattle silage. Apart from these applications, acetic acid is utilized in the production of inks and dyes, as well as the production of perfumes. It is also involved in the rubber and plastic production industries.

Ascorbic Acid


One of the most common and vital vitamins is vitamin C, often known as ascorbic acid. Vitamin C supplementation is necessary due to its preventive role, especially when pollution levels are high. Ascorbic acid is an organic molecule that occurs naturally and has antioxidant effects. It is a white solid that can seem yellowish in contaminated samples. It readily dissolves in water and produces moderately acidic solutions. One kind of vitamin C is ascorbic acid. Plants, particularly citrus fruits, tomatoes, and green vegetables, contain ascorbic acid. Scurvy is caused by a nutrient deficit in the human diet. Ascorbic acid and its sodium, potassium, and calcium salts are commonly used as antioxidant food additives. These compounds are water-soluble and thus cannot protect non-polar fats from oxidation. For this purpose, the fat-soluble esters of ascorbic acid with long-chain fatty acids can be used as food antioxidants.  Although ascorbic acid is most widely used as an antioxidant food additive, it also has non-food uses in photography, fluorescence microscopy, stain removal, and plastic manufacture. Every day, scientists and researchers uncover novel vitamin C functions. It is one of the most affordable therapy options for preserving and protecting humans from infections, toxification, autoimmune illnesses, and cancer development.

Citric Acid


Citric acid is the organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is one of the most common food preservatives and flavoring additives. It can be found naturally in citrus fruits but is also manufactured. Its name is derived from the fact that it’s an organic acid found in many fruits and vegetables, especially citrus fruits. Citric acid is a concentrated powder that is mostly valued for its sour flavor, preservative quality, medicinal properties, and ability to act as a pH buffer. For these reasons, citric acid is found on the ingredients list of many foods in your kitchen pantry, including preserves, candy, and crunchy snacks. It is also known as “sour salt” due to its flavor and similar appearance and texture to salt. Although citric acid can be found in large concentrations in many citrus fruits, such as lemons, extracting the acid from the fruit for commercial usage is not cost-effective. Furthermore, the demand for citric acid significantly outnumbers the available supply of citrus fruit. In 1917, American food chemist James Currie discovered certain strains of the mold Aspergillus niger could be efficient citric acid producers, and the pharmaceutical company Pfizer began industrial-level production using this technique two years later, followed by Citrique Belge in 1929.

Acetylsalicylic Acid


Commonly known as Aspirin, acetylsalicylic acid is a medicinal organic compound used to treat conditions such as fever, pain, and inflammation. It is a carboxylic acid with the chemical formula CH3COOC6H4COOH. Acetylsalicylic acid has both anti-inflammatory and antipyretic effects. This drug also inhibits platelet aggregation and is used in the prevention of blood clots stroke, and myocardial infarction. In fact, aspirin is given shortly after a heart attack to reduce the risk of death. Aspirin as a chemoprotective drug has been found to reduce overall cancer incidence and mortality in colorectal, esophageal, and gastric cancers, with minor effects on prostate, breast, and lung cancers. The main undesirable side effects of aspirin taken by mouth are gastrointestinal ulcers, stomach bleeding, and tinnitus, especially in higher doses. Moreover, acetylsalicylic acid is a very common cause of accidental poisoning in young children, and therefore, it is advised to be kept out of reach from young children, toddlers, and infants.

Oxalic Acid


Oxalic acid is an organic compound having the formula HOOC-COOH and the IUPAC name ethanedioic acid. It is a white crystalline solid that dissolves in water to generate a colorless solution. The most common natural sources of oxalic acid are rhubarb, spinach, beet leaves, Swiss chard, chocolate, cabbage, sweet potatoes, peanuts, cranberries, strawberries, and bell peppers. It is also excreted as a metabolic product by a variety of aerobic bacteria (Penicillium and Aspergillus), molds, and Lichen. Its general structure is having two polymorphs and due to this, it appears as a white crystalline solid. It is popularly useful as a reducing agent and works as the chelating agent with oxalate as its conjugate base. Oxalic acid is also a part of pollution and acid rain. Sawdust or the treatment of carbon monoxide with sodium hydroxide are used to make oxalic acid synthetically. About 25% of produced oxalic acid is used as a mordant in dyeing processes. It is also used in bleaches, especially for pulpwood, and for rust removal and other cleanings, in baking powder, and as the third reagent in silica analysis instruments. In lanthanide chemistry, oxalic acid is a crucial reagent. In very strongly acidic solutions, hydrated lanthanide oxalates form rapidly in a densely crystalline, easily filtered form that is mainly free of nonlanthanide elements. The oxides, which are the most generally marketed form of these elements, are formed by the thermal breakdown of these oxalates.

Lactic Acid


Most of us are familiar with the intense pain caused by overdoing a strenuous activity. In particular, the pain is caused by a carboxylic acid known as Lactic acid. It is an alpha-hydroxy acid (AHA) due to the presence of a hydroxyl group adjacent to the carboxyl group. It is most commonly found in fermented milk products such as sour milk, cheese, and buttermilk. First isolated in 1780 by a Swedish chemist, Carl Wilhelm Scheele, lactic acid is manufactured by the fermentation of molasses, starch, or whey in the presence of alkaline substances such as lime or calcium carbonate. In our body, lactic acid is produced in the blood (in the form of lactates) when glycogen is broken down in the muscle. Increased acidic levels due to the anaerobic respiration during a strenuous are believed to cause muscle soreness; however, the true source of pain is still unclear. Lactic acid is utilized as a flavoring agent and preservative in processed cheese, salad dressings, pickles, and carbonated beverages, as well as a raw material or catalyst in a variety of chemical processes. Lactic acid is also employed in pharmaceutical technology to produce water-soluble lactates from otherwise-insoluble active ingredients. It finds further use in topical preparations and cosmetics to adjust acidity and for its disinfectant and keratolytic properties.

Tartaric Acid


Tartaric acid is a white crystalline diprotic organic acid that occurs naturally in many plants, particularly in grapes, bananas, and tamarinds. . It is an alpha-hydroxy-carboxylic acid famously known for the prominent role it plays in maintaining the chemical stability of the wine and its color and finally in influencing the taste of the finished wine. Tartaric acid also played an important role in the discovery of chemical chirality. As an acidulant, it has a naturally sour taste and imparts a strong sour flavor to dishes. Tartaric acid can also aid in the setting of gels and the preservation of foods like carbonated beverages, fruit jellies, gelatin, and effervescent tablets. Industrially, tartaric acid is used in the plating of gold and silver, the cleaning and polishing of metals, the tanning of leather, and the production of blue ink for blueprints. Rochelle Salt contains tartaric acid, which combines with silver nitrate to produce the silvering on mirrors. In medical analysis, tartaric acid is used to make solutions for the determination of glucose.

Formic Acid

Methanoic acid, also known as formic acid (HCOOH) is a colorless, corrosive liquid with a pungent odor. It is completely miscible with water and many polar solvents but only partially miscible with hydrocarbons. Formic acid derives its name from ants from which it was first obtained by dry distillation. Formic acid is also prepared in the form of its esters by treatment of carbon monoxide with an alcohol such as methanol (methyl alcohol) in the presence of a catalyst. Formic acid is not a normal carboxylic acid; it is characterized by its acid strength, lack of anhydride formation, and reactivity as a reducing agent—a trait owing to the CHO group, which gives certain aldehyde-like characteristics. Formic acid is commercially manufactured in its methyl and ethyl esters. Formic acid is dehydrated into carbon monoxide by concentrated sulfuric acid. Formic acid and its salts are used primarily in the feed industry, grass silage, leather tanning, and anti-icing. Other applications include textile dyeing and finishing, food additives, natural rubber, drilling fluids, and various chemical processes.

Stearic Acid


Stearic Acid, also known as Octadecanoic Acid, is a waxy solid obtained from animal and vegetable fats and oils with the chemical formula {C}_{17}{H}_{35}{COOH}.  Commercial stearic acid is a mixture of approximately equal amounts of stearic and palmitic acids and small amounts of oleic acid. The structure of stearic acid, which includes both polar and non-polar components. This feature, with a polar head group that can connect to metal cations and a nonpolar chain that confers solubility in organic solvents, is used in a variety of applications. As a result, it can be used as a surfactant and a softening agent. Stearic acid undergoes the standard reactions of saturated carboxylic acids, the most famous of which is stearyl alcohol reduction, as well as esterification with a variety of alcohols. Stearic acid also has occlusive properties which means that it ensures hydration for the skin through the prevention or delaying of loss of moisture from the surface of your skin. This property makes it widely employable in various personal care products ranging from moisturizing creams to aftershave lotions. The fat cells present in stearic acid attach themselves to the aromatic compounds present in the candles. This helps the fragrance to last longer as it prevents the aroma from gushing out of the candle in one go. Stearic acid is used as a negative plate additive in lead-acid batteries because it improves the plate’s hydrophobicity, which is important when the battery has to be dry-charged. When the plates are left to dry in the open following the tank creation process, the stearic acid aids to reduce the oxidation extension of the negative active material, or the lead that forms anew.

Adipic Acid


Adipic acid, also known as hexanedioic acid, is a white crystalline solid with the chemical formula {(CH}_{2})_{4}{(COOH)}_{2} and melting temperature 152 ºC. Adipic acid is a straight-chain dicarboxylic acid that exists as a white crystalline compound at standard temperature and pressure. In the polymer industry, adipic acid is one of the most valued monomers feedstocks for producing resins, nylons, lubricants, and plasticizers. Almost 60 percent of adipic acid produced is used in the production of nylon 66. In the food industry, the use of adipic acid in foods imparts a smooth texture and tart taste in gelatines, desserts, and other foods that require acidulation. In addition, adipic acid is used in formulation in the field of pH regulator and buffer and used as laboratory chemicals.

Fatty Acids


Schematic diagram of a triglyceride with a saturated fatty acid (top), a monounsaturated one (middle), and a polyunsaturated one (bottom).

Fatty acids are the building blocks of the fat in our bodies and in the food we eat. During digestion, the body breaks down fats into fatty acids, which can then be absorbed into the blood. Fatty acid molecules are usually joined together in groups of three, forming a molecule called a triglyceride. In chemistry, fats (oils) often refer specifically to triglycerides (esters composed of three fatty acid units joined to glycerol, trihydroxy alcohol). They are primarily classified into two categories: saturated and unsaturated. Triglycerides are also made in our bodies from the carbohydrates that we eat.  Fatty acids have many important functions in the body, including energy storage. Humans can synthesize several fatty acids on their own, except for some polyunsaturated fatty acids known as essential fatty acids, which must be obtained from the diet.  The most abundant fatty acid is oleic acid, which is also the main component of olive oil. Research has linked oleic acid to reduced inflammation and it may have beneficial effects on cancer

Lauric Acid


Lauric acid is inexpensive, non-toxic, and safe to handle carboxylic acid often used in laboratory investigations of melting-point depression. It is a saturated fat with a 12-carbon atom chain commonly found in many vegetable fats, particularly in coconut and palm kernel oils. Lauric acid is a solid at room temperature but melts easily in boiling water. It is mostly used in the manufacturing of soaps and cosmetics. Lauric acid is reacted with sodium hydroxide to produce a soap called sodium laurate. In the medical field, lauric acid is used to treat viral illnesses such as influenza (the flu), swine flu, avian flu, the common cold, herpes simplex virus (HSV)-induced fever blisters, cold sores, and genital herpes; human papillomavirus (HPV)-induced genital warts; and HIV/AIDS. It’s also used to keep HIV from being passed on from moms to their children.

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