月: 2023年1月

What Is Acetic Acid?

Figure 1. Basic Information on Acetic Acid

Acetic acid, also known as ethanoic acid, is an organic compound that is the main ingredient in vinegar and a type of carboxylic acid. It is characterized as a typical weak acid, presenting as a clear, colorless liquid with a strong sour taste and pungent odor. Produced via chemical synthesis and bacterial fermentation, its synthetic production often involves the carbonylation of methanol, or through the dry distillation of wood.

Acetic acid’s applications span from dyeing and synthetic vinegar to photo-fixing solutions. It is important to note that acetic acid-water mixtures are highly corrosive and require careful handling.

Uses of Acetic Acid

Acetic acid serves primarily as a raw material for chemical synthesis, contributing to the production of vinyl acetate, acetic anhydride, acetone, and various acetic esters and pharmaceuticals. It is instrumental in manufacturing synthetic resins from vinyl acetate and paints from acetic esters, with acetic anhydride acting as a significant acetylation agent for producing acetyl cellulose.

Beyond industrial applications, acetic acid enhances food flavors as a seasoning in vinegar, pickles, and sauces, and is used in flavoring and fragrance manufacturing.

Properties of Acetic Acid

With a melting point of 16.7°C and a boiling point of 118°C, acetic acid is miscible with water, ethanol, ethyl acetate, acetonitrile, chloroform, ether, and benzene, but insoluble in longer-chain hydrocarbons and carbon disulfide. High purity acetic acid, known as glacial acetic acid, crystallizes at low temperatures. Dehydration and condensation of acetic acid molecules result in acetic anhydride.

Structure of Acetic Acid

Figure 2. Structure of the Dimer of Acetic Acid

The molecular formula for acetic acid is CH₃COOH, featuring carbon and oxygen atoms in the same plane, with bond angles of 119° for C-C-OH and C-C=O, and 122° for O=C-OH. Hydrogen bonding between acetic acid molecules forms a cyclic dimer, observable in gaseous state via electron diffraction and in solid state through X-ray crystallography. In its pure liquid state, acetic acid exists as dimers or polymers, forming dimers in nonprotic solvents and existing as monomers in protic solvents.

Other Information on Acetic Acid

1. Reaction of Acetic Acid

Acetic acid participates in neutralization reactions with bases, producing compounds such as potassium acetate when neutralized with potassium carbonate. It undergoes esterification when heated with alcohols in the presence of sulfuric acid, a process known as Fischer esterification. Additionally, acetic acid can react with chlorine under sunlight to form chloroacetic acid, along with dichloroacetic and trichloroacetic acids as byproducts.

2. Synthesis of Acetic Anhydride

Figure 3. Synthesis of Acetic Anhydride

Acetic anhydride, a carboxylic anhydride, is formed through the dehydration-condensation of acetic acid molecules. It is used as a raw material in the production of cellulose acetate fiber, pharmaceuticals like aspirin, and synthetic materials for fragrances and dyes.

What Is Tartaric Acid?

Tartaric acid, a hydroxycarboxylic acid with the formula C₄H₆O₆, is known for its presence in many plants, especially grapes. It has a molecular weight of 150.1 and is also referred to as 2,3-dihydroxy succinic acid due to its specific structural arrangement. This acid is unique because it contains two chiral carbon atoms, leading to the existence of three isomers: L-tartaric acid, D-tartaric acid, and meso-tartaric acid, with L-tartaric acid being the most prevalent in nature.

Racemic tartaric acid, or grape acid, is a 1:1 mixture of the L- and D-forms. The melting points vary across these forms, with the L- and D-forms melting at 170°C, the meso-form at 151°C, and the racemic form at 206°C. Their CAS numbers are specific to each form, illustrating their distinct chemical identities.

Properties of Tartaric Acid

As a colorless solid, tartaric acid is soluble in polar solvents, with the racemic form being an exception in water solubility. Its production primarily involves the synthesis from potassium hydrogen tartrate, a byproduct of winemaking, through various chemical processes including the addition of calcium hydroxide or calcium carbonate, followed by extraction and acidification to yield tartaric acid.

Alternative synthetic methods involve the oxidation of maleic acid or fumaric acid, though these have not seen widespread practical application.

Uses of Tartaric Acid

Commonly used as a food additive, tartaric acid imparts a refreshing sour taste to soft drinks, jellies, jams, and sauces. Its salts, potassium hydrogen tartrate and sodium tartrate, serve as leavening agents that release carbon dioxide upon heating. In cosmetics, tartaric acid adjusts pH and acts as an astringent. It plays a role in organic synthesis as a naturally occurring asymmetric catalyst, notably in Sharpless oxidation for the specific synthesis of epoxides.

Other Information on Tartaric Acid

1. Origin of Tartaric Acid

The term “tartaric acid” was derived from its discovery in tartar, a sediment produced in winemaking. It is found in various natural sources, predominantly in grapes, and is characterized by a slight bitterness and sharp acidity.

2. Tartaric Acid and Its Mirror-Image Isomers

In 1849, Louis Pasteur’s isolation and study of tartaric acid salt crystals revealed the existence of mirror-image isomers. This discovery, illustrating that these isomers rotate polarized light in opposite directions, significantly contributed to the development of stereochemistry.

What Is Hydrogen Peroxide?

Hydrogen peroxide is a colorless compound with the chemical formula H₂O₂, known for its weak, characteristic ozone smell.

Discovered by French chemist Tenard in 1818, hydrogen peroxide is celebrated as an eco-friendly chemical. Its decomposition into water and oxygen eliminates concerns about environmental pollution.

Uses of Hydrogen Peroxide

Containing activated oxygen, hydrogen peroxide is utilized for bleaching, chemical reactions, sterilization, and deodorization.

1. Bleaching

In response to growing environmental awareness, the demand for chlorine-free bleaching methods, especially in the paper and pulp industry, is on the rise. Hydrogen peroxide offers a shorter bleaching process while maintaining quality, making it ideal for cellulose-based fibers.

2. Deodorization and Corrosion Prevention

It effectively oxidizes hydrogen sulfide produced in sewage treatment plants, facilitating deodorization and detoxification.

3. Soil Improvement

Oxidation of organic contaminants in soil can expedite soil purification.

4. Surface Treatment

Hydrogen peroxide is employed for the soft etching of printed circuit boards and similar applications.

5. Sterilization

For safety reasons, hydrogen peroxide has replaced formaldehyde in disinfection and sterilization processes. It cleans and sterilizes food production equipment and containers. Oxidol, used for skin abrasions disinfection, contains diluted hydrogen peroxide.

6. Refining

Adding hydrogen peroxide to metal salt solutions, like those of copper, zinc, and nickel containing iron impurities, enables iron recovery as a precipitate, aiding in metal refining.

7. Oxidizing Agent

Hydrogen peroxide serves as a neutral, environmentally friendly oxidant, substituting chlorine-based oxidants in the production of various chemicals, including organic peroxides and sodium chlorite.

• Oxidation of phenol to produce hydroquinone and catechol
• Oxidation of acrolein or methacrolein to produce methacrylic acid or methacrylate
• Conversion of veratraldehyde to p-cresol
• Transformation of cyclohexanone into higher dibasic acid esters
• Production of L-Tartaric Acid from Maleic Anhydride

Properties of Hydrogen Peroxide

At room temperature, hydrogen peroxide is a colorless liquid with a molecular weight of 34.02. Its aqueous solutions have specific gravities and melting and boiling points varying by concentration. It is soluble in alcohol and ether and requires careful handling due to explosiveness at concentrations above 66%. Decomposition into water and oxygen can be catalyzed by substances like manganese dioxide.

In acidic solutions, hydrogen peroxide acts as a potent oxidizing agent, while it can serve as a reducing agent in basic solutions. Its known derivatives include peracetic acid, caroic acid, and potassium persulfate.

Structure of Hydrogen Peroxide

The molecule of hydrogen peroxide features a bond between two oxygen atoms. This peroxide bond is characterized by repulsion between non-covalent electron pairs and minimal overlap of covalent pairs, resulting in low bonding energy.

Other Information on Hydrogen Peroxide

Methods of Producing Hydrogen Peroxide

1. Auto-Oxidation Method
The anthraquinone autoxidation method, developed by Kemira in Finland, is the predominant global production process.

2. Direct Synthesis Method
This method synthesizes hydrogen peroxide from hydrogen and oxygen under pressure, using a catalyst.

3. Oxygen Reduction Method
Oxygen gas is introduced at the cathode during sodium hydroxide electrolysis, yielding hydrogen peroxide.

4. Electrolysis Method
Electrolyzing ammonium hydrogen sulfate produces hydrogen peroxide from the resultant ammonium persulfate.

5. Alcohol Oxidation Method
Hydrogen peroxide is obtained through the oxidation of isopropanol.

What Is Sodium Peroxide?

Sodium peroxide, Na₂O₂, is a sodium-based peroxide with various hydrate states. It is known for its antibacterial, bleaching, and deodorizing properties, making it valuable in household and industrial applications. Its CAS number is 1313-60-6.

Uses of Sodium Peroxide

Utilized as a bleaching agent for fibers, bones, and laundry, sodium peroxide is also employed in air purification in submarines, production of organic peroxides, and as a safe, odorless detergent. It is typically sold in powder form for ease of use.

Properties of Sodium Peroxide

Anhydrate sodium peroxide is a pale-yellow crystal with a melting point of 460°C and a boiling point of 675°C. It reacts exothermically with water and ignites upon contact with flammables. The octahydrate form is colorless and crystalline.

Types of Sodium Peroxide

Available in various quantities for research and industrial use, it is hygroscopic and requires careful handling and storage.

Other Information on Sodium Peroxide

1. Synthesis of Sodium Peroxide

Produced by heating metallic sodium in dry air or by reacting hydrogen peroxide with sodium hydroxide solution.

2. Chemical Reaction of Sodium Peroxide

Reacts violently with water to produce sodium hydroxide and hydrogen peroxide, and absorbs CO₂ to form sodium carbonate. It is a strong oxidizing agent that should be kept away from moisture and combustibles.

3. Regulatory Information on Sodium Peroxide

Classified under various safety regulations, handling of sodium peroxide must adhere to legal standards due to its hazardous nature.

What Is Peracetic Acid?

Peracetic acid, a colorless liquid with a pungent odor, is produced by reacting acetic anhydride with hydrogen peroxide and sulfuric acid, or by oxidizing acetaldehyde with oxygen. It is stable in dilute solutions but explosive at temperatures above 110°C and corrosive to skin.

Uses of Peracetic Acid

Effective against a broad spectrum of microorganisms, peracetic acid is used as a disinfectant in the medical field for sterilizing endoscopes and dialysis equipment, and in the food industry for sterilizing packaging and controlling microbial growth on produce and meats. It also serves as an epoxidation agent and bleaching agent.

Properties of Peracetic Acid

Soluble in ethanol and ether, peracetic acid decomposes into acetic acid and hydrogen peroxide when mixed with water. It has a melting point of 0.1°C and a boiling point of 105°C.

Other Information on Peracetic Acid

1. Related Compounds of Peracetic Acid

Part of the percarboxylic acid family, peracetic acid is named for its peroxy bond. Similar compounds include perbenzoic acid, a percarboxylic acid derived from benzoic acid.

2. Reactivity of Peracetic Acid

Used in organic synthesis as an oxidant, peracetic acid’s high purity form is explosive, making the less hazardous mCPBA a safer alternative.

3. Reaction of Percarboxylic Acid

Peracetic acid releases a single oxygen atom in reactions, such as epoxidation of olefins, Baeyer-Villiger oxidation of ketones to esters, and oxidation of amines to amine oxides.

What Is Sodium Perchlorate?

Sodium perchlorate with the chemical formula NaClO₄, is a sodium salt of perchloric acid, produced via the electrolysis of sodium chlorate. Recognized for its oxidizing properties, it plays a crucial role in various perchlorate applications, distinguished by its large ionic radius in aqueous solutions. It is cataloged under CAS numbers 7601-89-0 (anhydrous) and 7791-07-3 (monohydrate).

Uses of Sodium Perchlorate

Primarily, sodium perchlorate is used in synthesizing other perchlorates due to its high-water solubility. It finds applications in explosives, as an oxidizing agent, and in the stabilization of synthetic resins. Additionally, it serves as an analytical reagent in nucleic acid extraction and as an eluent in high-performance liquid chromatography (HPLC).

Properties of Sodium Perchlorate

1. Appearance and Solubility

Appearing as a white crystalline powder, sodium perchlorate is highly soluble in water and alcohol, exhibiting deliquescent properties.

2. Oxidizing Power

Its oxidizing capability is attributed to chlorine being in its highest oxidation state (+7), enabling it to oxidize other substances while reducing itself.

3. Thermal Behavior and Fire Hazard

Decomposing above 200°C to release oxygen, it poses a fire risk, especially when in contact with organic materials, and can exacerbate fires by generating oxygen during decomposition.

4. Chaotropic Nature

Sodium perchlorate acts as a chaotropic agent, disrupting the hydrogen-bonded network of water molecules. This property is exploited in the purification of proteins and nucleic acids, facilitating their precipitation or adsorption by destabilizing hydration shells.

Other Information on Sodium Perchlorate

1. Ion-Pair Liquid Chromatography

As an ion-pair reagent, sodium perchlorate improves ion-pair liquid chromatography’s analytical performance by forming stable associations with organic cations, minimizing unwanted column interactions.

2. Hazards and Toxicity

Its oxidizing nature can lead to fires or explosions when mixed with organic materials. It poses health risks, including skin and eye irritation, respiratory tract irritation, and potential long-term blood system damage.

3. Environmental Impact

Perchlorate’s environmental persistence necessitates careful management to prevent adverse ecological effects.

4. Regulation and Compliance

Regulated under multiple legislations, sodium perchlorate is recognized as a Class 1 Oxidizing Solid under the Fire Service Act and classified under various safety and health regulations, emphasizing the need for strict handling and storage protocols.

What Is Potassium Perchlorate?

Potassium perchlorate, with the chemical formula KClO₄, is a potassium salt of perchloric acid. As an oxidizing agent common to perchlorates, it exhibits significant oxidizing properties. Its CAS number is 7778-74-7.

Uses of Potassium Perchlorate

Historically used in solid-fuel rockets, potassium perchlorate is now employed in explosives, fireworks, and as a raw material for signal flares, owing to its ability to produce intense flames. Additionally, it serves as an analytical reagent in ion-pair chromatography and in medical applications as an antithyroid drug.

Properties of Potassium Perchlorate

1. Appearance and Solubility

This compound appears as a colorless or white crystalline powder, insoluble in water and almost insoluble in ethanol, requiring a large volume of cold water to dissolve.

2. Crystal Stability

Unlike sodium perchlorate, potassium perchlorate is stable in crystalline form, not exhibiting deliquescence.

3. Thermal Behavior and Fire Hazard

Upon heating above 400℃, potassium perchlorate decomposes, releasing oxygen. This can oxidize organic matter, posing fire risks and exacerbating fires by supplying oxygen.

4. Oxidizing Power

Its oxidizing ability is attributed to chlorine being in its highest oxidation state (+7), enabling it to oxidize other substances while reducing itself.

Other Information on Potassium Perchlorate

1. Iodine Uptake Inhibition

By competing with iodine ions for uptake transporters, potassium perchlorate can modulate thyroid function, leveraging its similarity in ionic size to iodine. This is utilized both therapeutically and diagnostically in thyroid management.

2. Ion-Pair Liquid Chromatography

As an ion-pair reagent, potassium perchlorate enhances the performance of ion-pair liquid chromatography by stabilizing associations with organic cations, minimizing unwanted column interactions.

3. Hazards and Toxicity

Potassium perchlorate’s oxidizing nature can lead to fires or explosions when in contact with organic materials. It poses risks of skin and eye irritation, respiratory irritation, and blood system damage upon long-term exposure.

4. Regulations

It is regulated under multiple laws, including the Industrial Safety and Health Law and the Fire Service Law, as a hazardous oxidizing substance and a Class 1 oxidizing solid, respectively. Additionally, it is recognized under transportation and chemical substance control regulations.

What Is Perchloric Acid?

Perchloric acid, a halogenated acid with the formula HClO₄, is known for its strong oxidizing properties. It is a colorless, fuming liquid at room temperature, typically available in 60-70% aqueous solutions due to its high hazard levels. It has a CAS number of 7601-90-3 and a molecular weight of 100.46.

Uses of Perchloric Acid

Perchloric acid serves as an analytical reagent, particularly in ion exchange chromatography, and as a catalyst in organic synthesis. It is also used for dissolving metals, alloys, ores, and in the production of perchlorates like ammonium perchlorate, a component in rocket and missile propellants. Its applications extend to propellants, air bags, fireworks, and the electropolishing of metals.

1. Analytical Chemistry

Due to its high oxidizing power, perchloric acid is crucial for the decomposition of specimens with high organic content. It is always used alongside nitric acid to prevent explosions when in contact with organic materials. Additionally, it adjusts the dissociation pattern in ion exchange chromatography, influencing the retention time of substances.

2. Raw Materials for Perchlorate Production

Perchlorates, utilized in explosives and as oxidizing agents, are produced using perchloric acid. Ammonium perchlorate, specifically, is synthesized by reacting perchloric acid with ammonia, resulting in a substance used in rocket propellants.

Properties of Perchloric Acid

As a strong acid, perchloric acid poses risks of explosion when heated or mixed with organic matter. It is classified under several GHS categories, including Oxidizing Liquid Category 1 and Corrosive to Metals Category 1, indicating its potential for causing fire, explosion, and metal corrosion. It also poses serious health risks, including acute toxicity, skin and eye damage, suspected carcinogenicity, reproductive toxicity, and specific target organ toxicity.

For safety, perchloric acid should be stored in glass or polyethylene containers, away from direct sunlight, at room temperature, and in a well-ventilated area to minimize risks.

Other Information on Perchloric Acid

1. Toxic to Human Body

Due to its corrosive nature, perchloric acid requires the use of protective equipment, such as gloves and glasses, and should be handled in well-ventilated areas to avoid respiratory irritation.

2. Acidity of Perchloric Acid

Perchloric acid, with a pKa of -10, is the most acidic of the chlorine oxoacids, reflecting the increased stability of its chlorate ion upon proton dissociation. This high acidity makes it comparable to other strong acids like nitric and sulfuric acid.

What Is Periodic Acid?

Periodic acid, a type of iodine oxoacid, predominantly refers to orthoperiodic acid with the chemical formula H₅IO₆. It also encompasses metaperiodic acid (HIO₄), both sharing an oxidation number of +7 for iodine. These acids form periodates with various metals in solution, ionizing into periodate and hydrogen ions.

Uses of Periodic Acid

Primarily, periodic acid is utilized in the PAS reaction for polysaccharide detection, distinguishing between aldehydes and ketones using the Schiff reagent. This reaction decomposes polysaccharides into aldehydes, aiding in the detection of polysaccharides in organs. Additionally, periodic acid performs oxidative cleavage of diols into carbonyl compounds.

Properties of Periodic Acid

Metaperiodate sublimates at 100°C and decomposes at 138°C, forming iodic acid (HIO₃) and diiodine pentoxide (I₂O₅). Orthoperiodate, more stable and soluble in water, melts at 122°C and decomposes around 130-140°C. It is a weak acid, with significantly lower acidity than perchloric acid.

Structure of Periodic Acid

The structure of periodic acids varies between their forms. Metaperiodic acid features a one-dimensional chain-like structure, whereas orthoperiodate forms colorless monoclinic crystals with an octahedral structure centered on the iodine atom. In solution, a variety of periodate species exist, shifting with changes in temperature and pH.

Other Information on Periodic Acid

1. Synthesis of Periodic Acid

Orthoperiodic acid is synthesized through the reaction of barium hydrogen orthoperiodate with concentrated nitric acid, which upon heating, yields metaperiodic acid.

2. Reaction of Periodic Acid

Useful for the cleavage of 1,2-bifunctional compounds, periodic acid facilitates the Malaprade reaction—cleaving vicinal diols into aldehydes or ketones, crucial for carbohydrate structural analysis. This reaction is also applicable for selective RNA labeling and as a moderate oxidant in organic synthesis, exemplified by the Babler oxidation of secondary allylic alcohols.

What Is Potassium Permanganate?

Potassium permanganate is an inorganic compound with the chemical formula KMnO₄ and a molecular weight of 158.03. It has a density of 2.703 g/cm³, a decomposition point of 200°C, and a CAS number of 7722-64-7. This compound consists of potassium ions and permanganate ions.

The manganese in permanganate ion has an oxidation number of +7, making it a potent oxidizing agent. Classified as a hazardous substance under the Fire Service Law and as a toxic substance under the Industrial Safety Law, it must be labeled properly.

Uses of Potassium Permanganate

Known for its strong oxidizing properties, potassium permanganate is used in metal surface treatment, purification of acids, and tanker cleaning. In organic chemistry, it facilitates oxidation reactions, such as converting alcohols to ketones and aldehydes, cleaving alkenes to diols, and transforming alkyl groups on aromatic rings to carboxy groups. It also serves as a coloring reagent for TLC.

Additionally, it acts as an antiseptic and disinfectant, and is used in water purification and sewage treatment, reflecting its versatility in inhibiting microorganism growth and as a standard solution for redox titration.

Properties of Potassium Permanganate

At room temperature and pressure, potassium permanganate appears as purplish-black or greenish-black columnar rectangular crystals with a metallic luster, turning into a dark purplish-red solution when dissolved in water. It is highly soluble in water, slightly soluble in organic solvents like methanol and acetone, and in sulfuric acid, but decomposes in alcohol.

As one of the strongest oxidizers, it exhibits potent oxidation capabilities in both acidic and basic solutions. In acidic environments, it reduces to the light pink Mn²⁺ ion, while in basic solutions, it forms manganese dioxide (MnO₂), a brown precipitate.

Other Information on Potassium Permanganate

1. Production Process

The production of potassium permanganate involves melting manganese dioxide with KOH or K₂CO₃ and air oxidizing in a resistant container, or mixing with an oxidant like potassium chlorate for oxidation. After cooling, the synthesized potassium manganate is dissolved in water, filtered to remove impurities, and then treated with carbon dioxide to precipitate potassium permanganate, with potassium carbonate as a byproduct.

2. Hazards

Adding potassium permanganate to alcohol can cause a violent exothermic reaction, potentially melting containers or igniting combustible materials. It is crucial to avoid flammable materials and be cautious of oxidation and hazardous substance release. Mixing with concentrated sulfuric acid can produce explosive manganese oxide (Mn₂O₇), and adding hydrochloric acid to a concentrated solution or solid form generates toxic chlorine gas.