月: 2023年4月

What Is Thymine?

Thymine, a pyrimidine derivative, is one of the fundamental components of DNA.

DNA comprises four nucleotides: adenine (A), guanine (G), cytosine (C), and thymine (T), with thymine forming two hydrogen bonds with adenine.

Under ultraviolet light, DNA can mutate, forming dimers between adjacent thymine or cytosine bases. Thymine, along with cytosine and uracil, belongs to the pyrimidine base group.

Uses of Thymine

As a DNA component, thymine is crucial for storing the genetic blueprint of living organisms.

In polymerase chain reaction (PCR) testing, used for amplifying and detecting small amounts of genetic material like viruses, thymine is essential. This process requires supplying all four nucleotide types to synthesize a new DNA strand from the extracted gene.

Properties of Thymine

Thymine appears as a white crystalline powder, insoluble in cold water or ethanol but soluble in hot water, hot ethanol, and sodium hydroxide solution.

Oxidation by substances such as oxygen and free radicals can convert thymine into thymine glycol, potentially altering DNA structure. Although antioxidant enzymes and substances repair most cellular and DNA damage, excessive damage may lead to cancer and aging.

Structure of Thymine

Figure 1. Structural Formula of Thymine

Thymine’s structure includes a pyrimidine ring, characterized by nitrogen-containing six-membered rings, with imino groups at positions 1 and 3, carbonyl groups at positions 2 and 4, and a methyl group at position 5.

Figure 2. Hydrogen Bonds in DNA

The structure of thymine, particularly its imino and carbonyl groups, is pivotal for DNA’s double helix formation through hydrogen bonding.

Thymine is unique among nucleobases for having a methyl substituent and an allylic hydrogen, making it particularly reactive to oxidative stress in living organisms.

Other Information about Thymine

1. Nucleosides

Nucleosides, which are nucleobase-sugar compounds, include thymidine, formed from thymine and a pentacyclic sugar through a dehydration-condensation reaction involving an N-glycosidic bond.

Figure 3. Thymidine

Thymine derivatives include ribothymidine in tRNA and spongothymidine, an anti-herpes agent, synthesized through specific sugar modifications.

2. Nucleotides

Nucleotides, formed by attaching a phosphate group to a nucleoside, include thymidylate or thymidine monophosphate, derived from thymine.

3. Double Helix Structure of DNA

The double helix structure of DNA features hydrophobic bases, including thymine, on the inside with hydrophilic sugars and phosphates on the outside. This structure is stabilized by hydrogen bonds forming base pairs between adenine and thymine, and guanine and cytosine.

What Is Titanium Dioxide?

Titanium dioxide is an oxide of titanium represented by the chemical formula TiO2. It is the most stable of all titanium oxides. It is more commonly called titanium dioxide (IV). Other names include titanium dioxide, dioxotitanium(IV), and titanium(IV) dioxide, in addition to titanium(IV) oxide.

The main crystal structures of titanium dioxide are the anatase and rutile types. When the anatase type is heated above 1652°F (900ºC), it irreversibly transforms to the rutile type, which is a restable structure of titania. Titanium(IV) dioxide is soluble in hydrofluoric acid, hot concentrated sulfuric acid, and molten alkali salts. On the other hand, it is insoluble in other acids, alkalis, water, and organic solvents.

Naturally occurring as a by-product mineral of igneous and metamorphic rocks formed at high temperatures, titanium dioxide is produced as a mineral in the form of gold-red (rutile type), pyrite (anatase type), and plate titanite. In the industrial production of titanium dioxide, rutile ore or ilmenite ore (FeTiO3) is used as a raw material. Several production methods are known, known as the chlorine method and the sulfuric acid method.

Uses of Titanium Dioxide

The two basic uses of titanium dioxide are as pigments and photocatalysts. The rutile type is often used as a pigment and the anatase type as a photocatalyst.

First, titanium dioxide is used as a white pigment. The rutile type, which has low activity as a catalyst and excellent thermal stability, is used as a pigment in paints and is called titanium white, titanium white, or titanium white, and has high hiding power. The pigment’s classification name (color index name) is C.I. Pigment White 6. Specific applications include coloring pigments for paints, printing inks, inkjet inks, and plastics.

Titanium Dioxide is also used as a photocatalyst. When exposed to short-wavelength light equivalent to ultraviolet rays, titania reacts with water to produce reactive oxygen species. Reactive oxygen species have strong oxidizing power and decompose chemicals and bacteria. The anatase type has a larger band gap and is generally more active as a photocatalyst.

In addition, because of its low impact on the human body, it is used as a coloring agent (food additive) for foods, medicines, and cosmetics. It is also used as an artificial gemstone. Artificial crystals of titanium dioxide are colorless and transparent, and have a refractive index higher than that of tire diamonds. It is known by the trade name “titanium dioxide.” It is also used as a compounding material for silicone rubber, magnetic tape, and ceramics, as a photosensitive material for offset printing, and as a carrier for solid catalysts.

What Is Thiocyanate?

Thiocyanate, with the chemical formula HSCN, is also known as sulfocyanate or rhodanic acid. Contrary to being a volatile liquid, thiocyanate compounds typically exist as colorless salts and are not strong acids. These compounds are formed by the thiocyanate ion, SCN-, and are generally stable at room temperature.

Thiocyanate can produce toxic cyanide compounds when heated or reacts with strong bases and oxidizers. One of the hazardous products of such reactions is hydrogen cyanide, also known as hydrocyanic acid.

Naturally, thiocyanate occurs in some plants like onions, and it is also found in various salts and esters.

Uses of Thiocyanate

While not commonly used in its free acid form, thiocyanate salts have various industrial and chemical applications.

For instance, Potassium thiocyanate is utilized in producing thiourea, dyes, pharmaceuticals, textile dyeing, and photographic chemicals. Due to its endothermic dissolution in water, it can also serve as a refrigerant.

In analytical chemistry, adding thiocyanate ions to a solution containing iron(III) ions forms a distinctive blood-red complex, useful for qualitative testing.

What Is Thiosulfuric Acid?

Thiosulfuric acid is a sulfur oxoacid, composed of hydrogen and thiosulfuric ions.

With the chemical formula H2S2O3, this divalent inorganic acid has a molecular weight of 114.14. Its acid dissociation constants are pKa1 = 0.6 and pKa2 = 1.6. The salts of thiosulfuric acid, including those of ammonia, alkali, and alkaline earth metals, are highly soluble in water and relatively stable in neutral or alkaline solutions.

Isolating free thiosulfuric acid is challenging, as it decomposes into colloidal sulfur and sulfur dioxide in strongly acidic solutions. While it has been isolated as a diethyl ether complex at low temperatures and in liquid carbon dioxide, these are specialized conditions.

The free acid is highly unstable, decomposing into hydrogen sulfide and sulfur trioxide, even at low temperatures. Higher temperatures accelerate its decomposition into sulfur, sulfur dioxide, and water. In air, its decomposition products are more complex, reacting with water and oxygen to form additional compounds like sulfuric acid and polythionic acid.

Uses of Thiosulfuric Acid

Due to its instability, thiosulfuric acid is not used in its raw form industrially but rather as a salt.

For instance, anhydrous sodium thiosulfate is utilized as a dechlorinating agent, dyeing aid, chrome tanning reducer for leather, neutralizer for ballast water chemicals, bathing agent, and disposable body warmers. Both crystalline and aqueous solutions of sodium thiosulfate serve similar purposes.

Thiosulfuric acid is also used in synthesizing high-value amino acids like cysteine in bacterial bodies.

Principle of Thiosulfuric Acid

Thiosulfuric acid and its ions often act as redox and chelating agents for metals. A typical redox reaction involves the reduction of halogens, where the thiosulfuric acid ion converts to a sulfate ion, making sodium thiosulfate a useful titrant in iodine titration.

As a chelating agent, it solubilizes poorly soluble silver halides into silver thiosulfate complexes, aiding in the photo fixation process. In acidic solutions, thiosulfuric acid decomposes into sulfur dioxide, combining sulfur with sulfurous acid.

Types of Thiosulfuric Acid

Typically sold in salt form due to the difficulty of isolating the free acid, common types include sodium thiosulfate, magnesium thiosulfate, ammonium thiosulfate, and barium thiosulfate. These are available in various laboratory-friendly volumes like 25 g, 100 g, and 500 g.

The most prevalent product is sodium thiosulfate, available both as a solid and in aqueous solutions. For industrial use, “anhydrous sodium thiosulfate” is provided in larger quantities, such as 25 kg.

What Is Thiamazole?

Thiamazole is an organic compound that is a nitrogen-containing heterocyclic compound.

Its chemical formula is C4H6N2S. It has a five-membered ring molecular structure of thiourea in the molecule and is also a derivative of imidazole. Its other common name is methimazole, which is 1-methyl-3H-imidazole-2-thione, according to IUPAC nomenclature.

It has a molecular weight of 114.17 and a melting point of 294.8°F (146°C). It is a white to light yellowish brown crystalline powder to powdery solid at room temperature. It has a characteristic odor and is easily soluble in water. Its solubility in water is 2.75 mg/mL (at 20°C). It is soluble in chloroform, alcohols, and pyridine, slightly soluble in benzene, and insoluble in ether.

Decomposition produces toxic substances such as carbon dioxide, carbon monoxide, nitrogen oxides (NOx), and sulfur oxides (SOx). Therefore, when storing, it is necessary to avoid high temperatures, direct sunlight, and contact with strong oxidizers. Although there are no specific legal regulations, there is a possibility of allergic skin reactions and a suspicion of adverse effects on fertility or the fetus.

Uses of Thiamazole

Thiamazole is primarily used in antithyroid medications. It is most commonly used in the treatment of excessive thyroid hormone levels, i.e., in the treatment of hyperthyroidism.

Other uses include lowering blood thyroid hormone levels before therapeutic intervention, to minimize the effects of thyroid manipulation in thyroid surgery or radioactive iodine therapy. Thiamazole, as a drug, is considered to be fast-acting, has few side effects, and is considered a major first-line drug.

Originally developed as a drug for humans, it is now actively used to treat hyperthyroidism in cats. It is a mainstream therapeutic agent, especially in Europe and the United States. As a general organic compound, it is also used in synthetic organic chemistry.

Principle of Thiamazole

The structure of thiamazole differs depending on its application.

1. Thiamazole as an Antithyroid Drug

Thiamazole, as an antithyroid drug, inhibits thyroid hormone biosynthesis by blocking thyroid peroxidase, an enzyme in the thyroid gland. Biosynthesis of thyroxine, a type of thyroid hormone, requires iodination of thyroglobulin by thyroid peroxidase.

Thioamide compounds, including thiamazole, are believed to inhibit many steps in thyroid hormone biosynthesis, and one of the reactions inhibited by thiamazole is the iodination of thioglobulin.

One of the serious side effects caused by thiamazole is agranulocytosis. Agranulocytosis is a condition in which the number of white blood cells in the blood, especially neutrophils, drops. If a patient experiences fever or sore throat while taking thiamazole, agranulocytosis should be suspected immediately, and if agranulocytosis develops, thiamazole should be discontinued under medical supervision.

2. Thiamazole in Synthetic Organic Chemistry

In synthetic organic chemistry, thiamazole is also useful as a scavenger of free radicals, such as hydroxyl radicals (OH).

Types of Thiamazole

The types of thiamazole currently available include pharmaceuticals and chemical reagents. As a chemical reagent, thiamazole is sold in volumes of 5 g, 25 g, and 100 g. It is a reagent that can be stored at room temperature. It is used as a raw material for organic synthesis.

Thiamazole, as a pharmaceutical product, is used as an antithyroid drug, as mentioned above. It is marketed under the trade name Mercazole and is available at 2.5 mg and 5 mg. The dosage form is film-coated tablets. It is indicated for hyperthyroidism and requires a prescription from a physician.

What Is Thiazole?

Thiazole is a colorless to pale-yellow, transparent liquid at room temperature.

It is a heterocyclic aromatic compound with molecular formula C3H3NS and a molecular weight of 85.13. It has a characteristic unpleasant odor similar to pyridine. It is named by adding the prefix thia (thia-), meaning sulfur (S) in the ring, before azole, the name of a five-membered ring compound containing nitrogen (N). Heterocyclic aromatic compounds with S and N in the five-membered ring have two isomers: compounds with S and N adjacent (isothiazole: 1,2-thiazole) and compounds with S and N separated by one carbon (C) (thiazole: 1,3-thiazole).

It is found as a substructure of vitamin B1 (thiamine), epothilone, and other natural products. Sulfathiazole, also known as sulfa drugs (a generic term for synthetic antibacterial and chemotherapeutic agents containing a sulfonamide moiety), also contains a thiazole ring. Other thiazole azo dyes also contain a thiazole ring.

Uses of Thiazole

The main use of thiazole is as a raw material for organic synthesis.

In the thiazole ring, the 2-position reacts as a nucleophilic site and the 5-position as an electrophilic site. When a Grignard reagent or alkyl lithium is applied to thiazole, the hydrogen at the 2-position is removed and the thiazole is metalized. Also, when a nucleophile such as an amine is applied to 2-chlorothiazole, a substitution reaction occurs.

Many important derivatives of thiazole are used in industrial chemicals (vulcanization accelerators), fungicides, anthelmintics, pharmaceuticals, and dyes. Vulcanization is the bonding of rubber molecules together by sulfur to give the raw rubber high elasticity and usually requires a long time. Therefore, vulcanization accelerators are added. Thiazole-based vulcanization accelerators do not contaminate rubber and are suitable for transparent and colored products. They are also used in a variety of diene rubbers.

Regarding the use of thiazole as a disinfectant, since thiazole acts pharmacologically on microorganisms, it acts only when it is in direct contact with and absorbed by them. As a result, thiazole is used as an antiseptic in cosmetics, as a pesticide, and as a detergent in products in liquid or emulsion form.

Medicines containing the thiazole structure are mainly the antibiotic cefviron, the anticancer drug bleomycin, and thiamine (vitamin B1). It forms stable complexes with inorganic acids and mercuric chloride (II) and is therefore sold in various forms.

Other Information on Thiazole

1. Properties of Thiazole

It is a type of amine of heterocyclic aromatic compounds, but it is less basic than pyridine and other compounds. It has a melting point of -27.4°F (-33 °C), a boiling point of 244.4°F (118 °C), a flash point of 78.8°F (26 °C), a specific gravity of 1.2 g/mL (at 25 °C), a refractive index n20/D 1.538, and is liquid at room temperature. It is soluble in many organic solvents, such as ethanol and ether, and slightly soluble in water.

2. Thiazole Production Process

Thiazole is obtained by condensation of chloroacetaldehyde (ClCH2CHO) with thioformamide (HCSNH2).

It is also obtained by dehydrocyclization of N-(2-mercaptoethyl) amide with thionyl chloride and oxidation with DDQ. The thiazole ring found in natural products is thought to be formed by a similar transformation of cysteine-containing peptides in many cases.

3. Handling and Storage Precautions

Precautions for handling and storage are as follows:

• Since light and air must be avoided, fill the container with inert gas when storing.
• Keep the container tightly closed and store in a dry, well-ventilated area.
• Keep away from heat and ignition sources.
• Avoid mixing or contact with oxidizing agents or strong acids.
• Take measures against static electricity.
• Take care not to leak, overflow, or scatter, and do not unnecessarily generate vapor.
• Use ventilation and local exhaust ventilation when vapor or aerosol is generated.
• Wear protective gloves and glasses when using this product because of skin and eye irritation.
• In case of skin contact or eye contact, rinse continuously with plenty of water for several minutes

What Is Thiazolidine?

Thiazolidine is a heterocyclic compound with the chemical formula C3H7NS, identifiable by its CAS number 504-78-9. It is a clear, colorless liquid at room temperature, with a molecular weight of 89.16, a boiling point of 72~75℃, and a density of 1.131g/cm3. The flash point is 132.8°F (56°C). It’s crucial to handle Thiazolidine cautiously, as it produces hazardous decomposition products like carbon oxides, nitrogen oxides (NOx), and sulfur oxides when ignited. Stable under normal storage conditions, it should be kept away from heat, flame, sparks, and strong oxidizers.

Uses of Thiazolidine

While Thiazolidine itself is not commonly used, its derivatives are significant in pharmaceuticals, particularly in β-lactam antibiotics like penicillin and thiazolidinedione (TZD) diabetes drugs. Thiazolidinedione drugs, used in treating type 2 diabetes, improve insulin resistance by binding to PPAR-gamma, a nuclear receptor, and function as transcriptional regulators. These drugs are mainly effective in reducing insulin resistance in peripheral tissues.

Principle of Thiazolidine

Thiazolidine can be synthesized through the hydrolysis of phthalimidoethyl mercaptan or by the condensation reaction of thiols with aldehydes or ketones. This reaction is reversible, leading to the instability of many Thiazolidine derivatives, which easily hydrolyze in water to yield thiols and aldehydes or ketones.

Types of Thiazolidine

1. Thiazolidine as a Reagent

As a chemical reagent, Thiazolidine is sold mainly for research and development in various capacities and can be stored at room temperature.

2. Thiazolidine Diabetes Drugs

Thiazolidinedione derivatives, used as diabetes medications, have seen varied market availability. While Troglitazone was withdrawn due to liver damage concerns, Pioglitazone Hydrochloride and Rosiglitazone remain in use, albeit with some restrictions due to potential health risks.

3. Thiazolidine in β-Lactam Antibiotics

The thiazolidine ring is a crucial component in many β-lactam antibiotics, including penicillin. These antibiotics function by inhibiting bacterial cell wall synthesis, offering both bacteriostatic and bactericidal actions.

What Is Selenite?

Selenite, chemically known as calcium sulfate dihydrate, has the formula CaSO4·2H2O. It is a colorless to white mineral, often presenting in a transparent form. This mineral is a variety of gypsum, which occurs naturally as calcium sulfate dihydrate. Among its various forms, selenite stands out as a colorless, transparent single crystal, emitting a bluish-white illumination reminiscent of moonlight.

Other forms of gypsum include snowflake gypsum (alabaster), characterized by its fine-grained texture, and fiber gypsum, known for its fibrous structure.

Uses of Selenite

Selenite is popularly used as a gemstone, valued for its perceived healing properties, which are believed to enhance insight and intuition. It is commonly fashioned into bracelets and other jewelry items, with prices varying widely based on quality and size. Due to its solubility in water, susceptibility to moisture, and low hardness, selenite requires careful handling.

Beyond its aesthetic uses, calcium sulfate, the primary component of selenite, has diverse applications in industries such as construction (in wall paints and cement), ceramics, pharmaceuticals, and food production. It is also used in coagulating tofu and as a desiccant.

What Is Serine?

Serine (abbreviated as Ser) is a non-essential amino acid, meaning it can be synthesized by the human body. It is one of the 20 amino acids that constitute human proteins. First discovered in 1865 through the hydrolysis of sericin, a protein in silk, Serine plays a crucial role in the human body.

In the nervous system, Serine is a vital component of nerve cells in the brain. It serves as a precursor for phosphatidylserine, a key constituent of cell membranes. Additionally, Serine is abundant in the stratum corneum, the outermost layer of the skin, making it a significant moisturizing agent for skin hydration.

Uses of Serine

Serine finds extensive applications across various industries due to its beneficial properties:

• Cosmetics: Leveraging its moisturizing effects, Serine is incorporated into a wide range of cosmetic products, including lotions, body creams, hand creams, hair treatments, and facial cleansers.
• Food Industry: It enhances flavor in various food products and is often included in nutritional drinks, coupled with other amino acids, to boost nutritional value.
• Medical Applications: In the healthcare sector, Serine is utilized in amino acid preparations to manage liver failure and in supplements to improve nutritional status in patients with dietary deficiencies.

This amino acid’s versatility in enhancing health, nutrition, and skincare underscores its significance in both biological and commercial contexts.

What Is a Sulfonamide?

Sulfonamides are derivatives of alkyl sulfonic acid, synthesized through the reaction of sulfuryl chloride with ammonia or amine, characterized by the chemical structure R-SO₂-NR’R”. These compounds are notable for their stability against hydrolysis and hydride reduction, making them more resistant than carboxylic acid amides. They exist as aliphatic or aromatic types, depending on their carbon structure.

Uses of Sulfonamides

Sulfonamides find varied applications from serving as antibacterial agents in sulfa drugs to being used in artificial sweeteners like saccharin and plasticizers such as p-toluenesulfonamide. They work by inhibiting folic acid synthesis in microorganisms, effectively combating a range of bacteria, fungi, and certain parasites.

Properties of Sulfonamides

Typically appearing as a white to light yellow crystalline powder, sulfonamides are stable, have high melting points, and decompose to release ammonia when heated. They are soluble in water and several organic solvents, with their aqueous solutions being slightly acidic.

Other Information on Sulfonamides

1. Sulfonamide Resistance

Microorganisms can develop resistance to sulfonamides due to mutations in the folate biosynthetic enzyme, reducing the efficacy of these drugs.

2. Pharmacokinetics

Orally or topically administered sulfonamides are rapidly absorbed and distributed, metabolized in the liver, and excreted through the kidneys.

3. Precautions for Use

Usage during pregnancy or lactation is advised only if the benefits outweigh the risks, with special caution near delivery due to potential risks of neonatal and nuclear jaundice. Sulfonamides should be avoided by those with allergies to sulfonamide drugs, porphyria, and can cause side effects including hypersensitivity reactions and crystalluria, which may be mitigated by adequate hydration.

4. Sulfanilamide Skeleton

The sulfanilamide structure forms the backbone for various drugs, including thiazide diuretics and sulfonylurea diabetes medications. Those allergic to sulfonamides may also react to these classes of drugs.