What is acetic acid, and what is its chemical formula?

Acetic acid, systematically named ethanoic acid, is an acidic, colorless liquid and an organic compound. Its chemical formula is CH3COOH, which can also be written as CH3CO2H, C2H4O2, or HC2H3O2. It is the second simplest carboxylic acid, following formic acid.

What is the common name for acetic acid, and what is its significance in everyday life?

Acetic acid is the active component of vinegar. Vinegar has been produced since ancient times, making acetic acid one of the first acids to be manufactured in large quantities. Its presence is what gives vinegar its characteristic sour taste and pungent smell.

What are some major industrial applications of acetic acid?

Acetic acid is a vital chemical reagent and industrial chemical used in various fields. Its primary uses include the production of cellulose acetate for photographic film, polyvinyl acetate for wood glue, and synthetic fibers and fabrics. It is also used in household descaling agents and as a food additive.

What is the global demand for acetic acid, and how is it primarily produced?

The global demand for acetic acid is approximately 17.88 million metric tonnes per year. The majority of acetic acid worldwide is produced through the carbonylation of methanol, a process that involves reacting methanol with carbon monoxide.

What are the health hazards associated with the industrial production and use of acetic acid?

The production and industrial use of acetic acid can pose health hazards to workers. These include incidental skin damage and chronic respiratory injuries resulting from inhalation of its vapors.

What is the preferred IUPAC name for acetic acid, and what is the origin of its common name?

The preferred IUPAC name for acetic acid is ethanoic acid. The common name 'acetic acid' originates from the Latin word 'acetum,' meaning vinegar, reflecting its primary role in this substance.

What is meant by 'glacial acetic acid,' and why is it called that?

Glacial acetic acid refers to water-free, or anhydrous, acetic acid. It is named 'glacial' because, similar to ice, it forms solid, ice-like crystals when agitated slightly below room temperature (16.6 °C or 61.9 °F).

How is acetic acid commonly represented using symbols in chemistry?

A common symbol for acetic acid in chemistry is AcOH or HOAc. In this notation, 'Ac' represents the acetyl group (CH3CO-), which is a functional group derived from acetic acid. The conjugate base, acetate (CH3COO-), is often represented as AcO-.

What is the historical significance of vinegar and acetic acid?

Vinegar, a dilute solution of acetic acid, has been known since antiquity. It is likely the first acid to be produced in large quantities, arising naturally from the exposure of alcoholic beverages like beer and wine to air, due to the presence of acetic acid-producing bacteria.

How did ancient civilizations utilize acetic acid?

Ancient Greeks, like Theophrastus, described how vinegar (acetic acid) reacted with metals to create pigments such as lead carbonate and copper salts. The Romans used vinegar as an antiseptic and a remedy for various ailments, though they also inadvertently caused lead poisoning by boiling wine in lead pots, creating lead acetate.

What significant chemical synthesis involving acetic acid was achieved in the 19th century?

In 1845, the German chemist Hermann Kolbe successfully synthesized acetic acid from inorganic compounds for the first time. This achievement demonstrated that organic compounds could be created from simpler inorganic precursors, a key development in organic chemistry.

How did industrial production of acetic acid evolve in the early 20th century?

By the early 20th century, much of the glacial acetic acid was produced from pyroligneous liquor, a byproduct of wood distillation. This involved treating the liquor with milk of lime, forming calcium acetate, which was then acidified with sulfuric acid to recover the acetic acid.

What are the modern industrial processes for producing acetic acid?

The dominant modern method for acetic acid production is methanol carbonylation, using either rhodium-based (Monsanto process) or iridium-based (Cativa process) catalysts. Other methods include acetaldehyde oxidation, ethylene oxidation, and fermentation.

What is the Monsanto process for acetic acid production?

The Monsanto process, developed in the 1970s, uses a rhodium-based catalyst to convert methanol and carbon monoxide into acetic acid. It was a significant advancement as it operated efficiently at lower pressures and produced fewer by-products compared to earlier cobalt-catalyzed methods.

What is the Cativa process, and how does it compare to the Monsanto process?

The Cativa process, developed by BP Chemicals, uses an iridium-based catalyst promoted by promoters for greater efficiency. It is considered 'greener' and more efficient than the Monsanto process, largely replacing it in many production facilities.

How is acetic acid detected in the interstellar medium?

Interstellar acetic acid was first detected in the Sagittarius B2 molecular cloud using radio interferometers. It holds the distinction of being the first molecule discovered in the interstellar medium using solely radio interferometry, without the aid of single-dish radio telescopes.

What is the acidity of acetic acid in aqueous solution?

In aqueous solution, acetic acid is a weak monoprotic acid with a pKa value of 4.76. This means it only partially dissociates, releasing a proton (H+) and forming the acetate ion (CH3COO-).

What is the structure of acetic acid in different phases?

In solid form, acetic acid molecules link into chains via hydrogen bonds. In the vapor phase at higher temperatures, and to some extent in dilute solutions or pure liquid, acetic acid molecules can form dimers, also connected by hydrogen bonds.

How does acetic acid function as a solvent?

Liquid acetic acid is a hydrophilic, polar protic solvent, similar to water and ethanol. It is miscible with many polar and non-polar solvents, allowing it to dissolve a wide range of substances, including inorganic salts, sugars, oils, and non-polar compounds, making it useful in industrial processes like dimethyl terephthalate production.

What is the role of the acetyl group derived from acetic acid in biochemistry?

The acetyl group, derived from acetic acid, is fundamental to all life forms. When attached to coenzyme A (acetyl-CoA), it plays a central role in the metabolism of carbohydrates and fats, forming a key link in cellular energy production.

Does acetic acid occur naturally in triglycerides?

Unlike longer-chain fatty acids, acetic acid does not naturally occur in triglycerides, which are a type of fat. However, the synthetic triglyceride triacetin, used as a food additive and in cosmetics, is metabolized into glycerol and acetic acid in the body.

Which bacteria are responsible for producing acetic acid naturally?

Acetic acid bacteria, notably those from the genera Acetobacter and Clostridium acetobutylicum, naturally produce acetic acid. These bacteria are widespread in food, water, and soil, and are responsible for the spoilage of fruits and other foods, leading to acetic acid formation.

What is the primary use of acetic acid in the chemical industry?

The largest single use of acetic acid is in the production of vinyl acetate monomer (VAM). This application consumes about one-third of the world's acetic acid production and is crucial for manufacturing paints and adhesives.

What are acetate esters, and how are they produced?

Acetate esters, such as ethyl acetate and butyl acetate, are commonly used as solvents in inks, paints, and coatings. They are typically produced through the catalyzed reaction of acetic acid with the corresponding alcohol, a process known as Fischer esterification.

What is acetic anhydride, and how is it produced from acetic acid?

Acetic anhydride is formed by the condensation of two acetic acid molecules, involving the loss of a water molecule. The primary production method involves heating acetic acid to high temperatures (700-750 °C) to form ketene, which is then reacted with more acetic acid to yield the anhydride.

What are the main applications of acetic anhydride?

Acetic anhydride is a key acetylation agent, with its major application being the production of cellulose acetate. Cellulose acetate is used in synthetic textiles and photographic film. Acetic anhydride is also used as a reagent in the synthesis of other compounds, including heroin.

How is acetic acid used as a solvent in chemical reactions?

As a polar protic solvent, acetic acid is frequently used for recrystallization to purify organic compounds. It also serves as a solvent and nucleophile in reactions involving carbocations, such as the Wagner-Meerwein rearrangement in the synthesis of camphor.

What is the medical use of acetic acid in cervical cancer screening?

Acetic acid is employed in cervical cancer screening, particularly in developing regions. When applied to the cervix, areas that turn white indicate a positive test result, suggesting the presence of precancerous or cancerous cells.

What are the antiseptic properties of acetic acid?

Acetic acid, particularly in a 1% solution, acts as an effective antiseptic. It demonstrates broad-spectrum activity against various bacteria, including strains resistant to common antibiotics, and can be used to treat skin infections.

What is the typical concentration of acetic acid in vinegar?

Vinegar typically contains at least 4% acetic acid by mass. However, legal limits and specific uses can vary, with commercial food pickling often using more concentrated solutions than table vinegar.

What are the primary organic reactions acetic acid undergoes?

Acetic acid undergoes typical reactions of carboxylic acids, such as reacting with bases to form acetates and water. It can be converted to derivatives like acetyl chloride and acetic anhydride, and can form esters and amides through esterification and amidation reactions, respectively.

How does acetic acid react with metals?

Acetic acid is mildly corrosive to metals like iron, magnesium, and zinc, reacting to form hydrogen gas and metal acetates. However, aluminum is resistant due to a passivating oxide layer, making aluminum tanks suitable for transporting acetic acid.

What is the 'baking soda and vinegar' reaction?

The common reaction between baking soda (sodium bicarbonate) and vinegar (acetic acid) produces sodium acetate, carbon dioxide gas, and water. This is a classic example of an acid-base reaction where the acid neutralizes the base.

What are some commercially significant derivatives of acetic acid?

Commercially significant derivatives include sodium acetate (used in textiles and as a food preservative), copper(II) acetate (used as a pigment and fungicide), aluminum acetate and iron(II) acetate (used as dye mordants), and palladium(II) acetate (used as a catalyst).

What are halogenated acetic acids, and what are their uses?

Halogenated acetic acids include chloroacetic acid, dichloroacetic acid, and trichloroacetic acid. Chloroacetic acid is used in the production of indigo dye, while bromoacetic acid is esterified to ethyl bromoacetate. Trifluoroacetic acid is a common reagent in organic synthesis.

What are the effects of prolonged inhalation of acetic acid vapors?

Prolonged inhalation of acetic acid vapors can cause irritation to the eyes, nose, and throat. At higher concentrations (around 100 ppm), it can lead to marked lung irritation and potential damage to the lungs, eyes, and skin. Concentrations above 1000 ppm are intolerable.

How does the hazard level of acetic acid solutions change with concentration?

The hazards of acetic acid solutions increase significantly with concentration. Solutions between 10-25% are classified as skin irritants (H315). Concentrations from 25-90% are corrosive, causing severe skin burns and eye damage (H314). Solutions above 90% are also flammable (H226) and corrosive (H314).

What is the NFPA 704 rating for acetic acid?

The NFPA 704 diamond for acetic acid indicates a health hazard rating of 3 (short exposure could cause serious temporary or residual injury), a flammability rating of 2 (moderately heated or exposed to high ambient temperature before ignition), and an instability rating of 0 (normally stable).

What are the LD50 and LC50 values for acetic acid?

The LD50 (median lethal dose) for acetic acid via oral ingestion in rats is 3.31 g/kg. The LC50 (median lethal concentration) is 5620 ppm for mice (1-hour exposure) and 16000 ppm for rats (4-hour exposure).

What are the NIOSH recommended exposure limits for acetic acid?

The National Institute for Occupational Safety and Health (NIOSH) recommends a Time-Weighted Average (TWA) exposure limit of 10 ppm (25 mg/m³) for acetic acid. They also recommend a Short-Term (ST) limit of 15 ppm (37 mg/m³).

What is the IDLH value for acetic acid?

The Immediately Dangerous to Life or Health (IDLH) value for acetic acid is 50 ppm. This represents the concentration from which a person could escape without irreversible health effects within 30 minutes.

What is the pK_a of acetic acid?

The acid dissociation constant (pK_a) for acetic acid is 4.76. This value indicates that it is a weak acid, meaning it does not fully dissociate in water.

What is the chemical formula for the conjugate base of acetic acid?

The conjugate base of acetic acid is acetate, with the chemical formula CH3COO-. This ion is formed when acetic acid loses a proton (H+).

What is the flash point of acetic acid?

The flash point of acetic acid is 40 °C (104 °F). This is the lowest temperature at which its vapors can ignite in the presence of an ignition source.

What is the autoignition temperature of acetic acid?

The autoignition temperature of acetic acid is 427 °C (801 °F). This is the temperature at which it will ignite spontaneously without an external ignition source.

What are the explosive limits of acetic acid vapor in air?

Acetic acid vapor forms explosive mixtures with air within the concentration range of 4% to 16%.

What is the density of acetic acid in liquid and solid states?

The density of liquid acetic acid is 1.049 g/cm³, while the density of solid acetic acid is 1.27 g/cm³.

What is the boiling point of acetic acid?

Acetic acid boils at 118 to 119 °C (244 to 246 °F).

What is the melting point of acetic acid?

Acetic acid melts at 16 to 17 °C (61 to 62 °F), which is why anhydrous acetic acid is referred to as 'glacial'.

How is acetic acid used in the food industry?

In the food industry, acetic acid is used as a food additive, identified by the code E260. It functions as an acidity regulator and is commonly used as a condiment, most notably as the primary component of vinegar.

What is the role of acetic acid in the textile industry?

Acetic acid is used in the textile industry, primarily in the production of cellulose acetate. This material is derived from cellulose treated with acetic acid and acetic anhydride, and it is used to create synthetic fibers and photographic film.

Acetic Acid Wiki: Acetic Acid: The Ubiquitous Acid of Industry and Life

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Nomenclature

Naming Conventions

Acetic acid is known by several names reflecting its chemical nature and historical discovery. The most common and preferred IUPAC name is acetic acid. Systematically, it is known as ethanoic acid, derived from its two-carbon chain structure according to IUPAC rules. The name "acetic" itself originates from the Latin word acetum, meaning vinegar, highlighting its primary association.

Glacial Acetic Acid

The term glacial acetic acid refers to anhydrous (water-free) acetic acid. It is named for its tendency to form ice-like crystals upon slight cooling, below its melting point of 16.6 °C (61.9 °F). Even trace amounts of water significantly lower this freezing point, making truly water-free acetic acid challenging to maintain in ambient conditions.

Chemical Symbols

In organic chemistry, acetic acid is frequently represented by the symbol AcOH or HOAc. Here, 'Ac' serves as a pseudoelement symbol for the acetyl group (CH₃CO-). The conjugate base, acetate, is represented as AcO^-. It is important to distinguish 'Ac' for acetyl from 'Ac' for the element actinium; context typically prevents confusion.

Historical Significance

Ancient Origins

Vinegar, a dilute solution of acetic acid, has been known since antiquity. Its natural formation from the fermentation of alcoholic beverages made it one of the earliest acids produced and utilized by civilization. Ancient Greek philosophers like Theophrastus noted its reactions with metals to produce pigments, while Hippocrates used it as an antiseptic and remedy for various ailments.

Alchemical and Early Chemical Pursuits

Alchemists in the 16th century explored acetic acid's derivatives, such as its role in producing acetone. For centuries, the distinction between anhydrous "glacial" acetic acid and the acid found in vinegar was a point of confusion, eventually clarified by Pierre Adet. Hermann Kolbe's synthesis of acetic acid from inorganic compounds in 1845 marked a significant step in understanding its chemical structure.

Industrial Revolution and Modern Production

Early industrial production relied on wood distillation and the subsequent isolation of acetic acid from pyroligneous liquor. The 20th century saw the rise of synthetic routes, notably the oxidation of acetaldehyde and ethylene. The development of methanol carbonylation, particularly the rhodium-catalyzed Monsanto process and later the iridium-catalyzed Cativa process, revolutionized production, making it highly efficient and cost-effective, and is now the dominant global method.

Chemical Properties

Acidity and Ionization

Acetic acid is a weak monoprotic acid with a pKa of 4.76. In aqueous solutions, it partially ionizes, releasing a proton (H⁺) to form the acetate anion (CH₃COO^-). A typical 1.0 M solution, similar to household vinegar, is only about 0.4% dissociated, resulting in a pH of approximately 2.4.

Molecular Structure and Bonding

Acetic acid molecules exhibit significant intermolecular hydrogen bonding. In solid and liquid states, they often form cyclic dimers linked by hydrogen bonds. In the vapor phase, dimers are also present. This hydrogen bonding influences its physical properties, such as its relatively high boiling point and its ability to act as a protic solvent.

Solvent Characteristics

As a polar protic solvent, acetic acid is hydrophilic and miscible with water and many organic solvents. Its dielectric constant allows it to dissolve both polar and non-polar compounds, making it a versatile solvent in various industrial processes, including the production of terephthalic acid and in certain organic reactions like Friedel-Crafts alkylations.

Biochemical Relevance

The acetyl group derived from acetic acid is fundamental to all life forms. It is a key component of Acetyl-CoA, central to the metabolism of carbohydrates and fats. Acetic acid is also produced naturally by bacteria, such as Acetobacter, and plays a role in biological systems, including human vaginal lubrication.

Industrial Production Methods

Methanol Carbonylation

The dominant industrial method, accounting for approximately 75% of global production, is the carbonylation of methanol. This process reacts methanol (CH₃OH) with carbon monoxide (CO) using metal catalysts. The highly efficient rhodium-based Monsanto process and the even more advanced iridium-based Cativa process are key examples, largely replacing older methods due to higher yields and fewer by-products.

Acetaldehyde and Ethylene Oxidation

Historically significant, the oxidation of acetaldehyde (produced from acetylene hydration) was a primary route. Modern variations involve the direct oxidation of ethylene using palladium catalysts. While effective, these methods are often less economically competitive than methanol carbonylation for large-scale production.

Fermentation Routes

Biological processes remain crucial, particularly for vinegar production. Acetobacter species utilize oxidative fermentation of ethanol in the presence of oxygen. Anaerobic bacteria like Clostridium can directly convert sugars or one-carbon compounds to acetic acid. While potentially more efficient, these bacteria are less acid-tolerant, limiting their use to lower concentrations or specific applications.

Diverse Applications

Polymers and Materials

The largest single use of acetic acid is in producing vinyl acetate monomer (VAM), a precursor to polyvinyl acetate used in paints and adhesives. It's also vital for acetic anhydride production, which is essential for manufacturing cellulose acetate for textiles and photographic film.

Solvents and Reagents

Acetic acid and its esters (like ethyl acetate, butyl acetate) serve as important solvents in inks, paints, coatings, and industrial cleaning agents. It's also used as a reagent in organic synthesis, for recrystallization, and in the production of various chemical derivatives and intermediates.

Food and Medical

As the key component of vinegar (E260), acetic acid is widely used as a food preservative, acidity regulator, and condiment in pickling. Medically, it functions as an antiseptic, is used in cervical cancer screening (visual inspection with acetic acid), and is listed on the WHO Model List of Essential Medicines for treating otitis externa.

Chemical Reactivity

Organic Transformations

Acetic acid undergoes characteristic carboxylic acid reactions. It reacts with bases to form acetates and water. Reduction yields ethanol. Its hydroxyl group readily participates in substitution reactions, forming derivatives like acetyl chloride and acetic anhydride. Esterification with alcohols produces acetate esters, while amidation yields acetamides.

Inorganic Interactions

Acetic acid is mildly corrosive to many metals, reacting to form hydrogen gas and metal acetates. For instance, it reacts with magnesium to produce magnesium acetate. Its reaction with sodium bicarbonate is a common demonstration, producing sodium acetate, water, and carbon dioxide gas.

Thermal Decomposition

At high temperatures (above 440 °C), acetic acid decomposes. It can yield methane and carbon dioxide, or alternatively, ketene and water, depending on the specific conditions.

Health and Safety Considerations

Vapor Exposure

Inhalation of acetic acid vapors can cause irritation to the eyes, nose, and throat. Higher concentrations (above 100 ppm) can lead to significant respiratory irritation and potential lung damage. Prolonged exposure in occupational settings has been linked to chronic respiratory issues and skin irritation.

Solution Hazards

Concentrated acetic acid solutions (≥ 25%) are corrosive to the skin, potentially causing burns or blisters that may be delayed. Solutions above 90% concentration are also flammable liquids. Proper handling procedures, including appropriate personal protective equipment (PPE), are essential.

Hazard Classification

Globally Harmonized System (GHS) classification indicates that acetic acid solutions are irritating (H315) at lower concentrations (10-25%). Higher concentrations (25-90%) are classified as causing severe skin burns and eye damage (H314). Concentrated solutions (>90%) are additionally classified as flammable liquids (H226).

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References

Acetic acid that is manufactured by intent, rather than recovered from processing (such as the production of cellulose acetates, polyvinyl alcohol operations, and numerous acetic anhydride acylations).

IUPAC Provisional Recommendations 2004 Chapter P-12.1; page 4

Industrial Organic Chemicals, Harold A. Wittcoff, Bryan G. Reuben, Jeffery S. Plotkin

A full list of references for this article are available at the Acetic acid Wikipedia page

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This content has been generated by an AI model and is intended for educational and informational purposes only. While efforts have been made to ensure accuracy based on the provided source material, it may not be exhaustive or entirely up-to-date.

This is not professional chemical advice. The information presented here should not substitute for consultation with qualified chemists, safety professionals, or adherence to official safety data sheets and regulatory guidelines. Always exercise caution when handling chemicals and refer to authoritative sources for specific safety protocols and applications.

The creators of this page are not liable for any errors, omissions, or consequences arising from the use of this information.

Acetic Acid

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Nomenclature 🏷️

🗣️ Naming Conventions

🧊 Glacial Acetic Acid

📝 Chemical Symbols

Historical Significance ⏳

🏺 Ancient Origins

⚗️ Alchemical and Early Chemical Pursuits

🏭 Industrial Revolution and Modern Production

Chemical Properties 🔬

⚖️ Acidity and Ionization

🔗 Molecular Structure and Bonding

💧 Solvent Characteristics

🌿 Biochemical Relevance

Industrial Production Methods ⚙️

🔥 Methanol Carbonylation

💨 Acetaldehyde and Ethylene Oxidation

🦠 Fermentation Routes

Diverse Applications 💡

🎨 Polymers and Materials

🧴 Solvents and Reagents

🍽️ Food and Medical

Chemical Reactivity 🔄

🧪 Organic Transformations

⚡ Inorganic Interactions

🔥 Thermal Decomposition

Health and Safety Considerations ⚠️

💨 Vapor Exposure

🔥 Solution Hazards

📊 Hazard Classification

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❗ Important Information

Dive in with Flashcard Learning!

Nomenclature

Naming Conventions

Glacial Acetic Acid

Chemical Symbols

Historical Significance

Ancient Origins

Alchemical and Early Chemical Pursuits

Industrial Revolution and Modern Production

Chemical Properties

Acidity and Ionization

Molecular Structure and Bonding

Solvent Characteristics

Biochemical Relevance

Industrial Production Methods

Methanol Carbonylation

Acetaldehyde and Ethylene Oxidation

Fermentation Routes

Diverse Applications

Polymers and Materials

Solvents and Reagents

Food and Medical

Chemical Reactivity

Organic Transformations

Inorganic Interactions

Thermal Decomposition

Health and Safety Considerations

Vapor Exposure

Solution Hazards

Hazard Classification

Teacher's Corner

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Discover other topics to study!

References

Feedback & Support

Disclaimer

Important Information