Vicinal In chemistry vicinal stands for any two functional groups bonded to two adjacent carbon atoms. For example the molecule 2,3-dibromobutane carries two vicinal bromine atoms and 1,3-dibromobutane does not diols have hydroxyl groups attached to adjacent atoms. Examples of vicinal diol compounds are ethylene glycol Ethylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet tasting liquid and propylene glycol Propylene glycol, known also by the systematic name propane-1,2-diol, is an organic compound , usually a faintly sweet, and colorless clear viscous liquid that is hygroscopic and miscible with water, acetone, and chloroform. Geminal In chemistry, the term geminal refers to the relationship between two functional groups that are attached to the same atom. The prefix gem is applied to a chemical name to denote this relationship, as in a gem-dibromide diols have hydroxyl groups bonded to the same atom.
Contents |
General properties
In general, organic geminal diols readily dehydrate In chemistry, a dehydration reaction is usually defined as a chemical reaction that involves the loss of water from the reacting molecule. Dehydration reactions are a subset of elimination reactions. Because the hydroxyl group is a poor leaving group, having an Brønsted acid catalyst often helps by protonating the hydroxyl group to give the to form a carbonyl group. For example, carbonic acid Carbonic acid has the formula H2CO3. It is also a name sometimes given to solutions of carbon dioxide in water, which contain small amounts of H2CO3. The salts of carbonic acids are called bicarbonates (or hydrogen carbonates) and carbonates. It is a weak acid. Carbonic acid should never be confused with carbolic acid, an antiquated name for ((HO)2C=O) is unstable and has a tendency to convert to carbon dioxide Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state (CO2) and water (H2O). Nevertheless, in rare situations the chemical equilibrium In a chemical process, chemical equilibrium is the state in which the chemical activities or concentrations of the reactants and products have no net change over time. Usually, this would be the state that results when the forward chemical process proceeds at the same rate as their reverse reaction. The reaction rates of the forward and reverse is in favor of the geminal diol. For example, when formaldehyde Formaldehyde is a chemical compound with the formula CH2O. It is the simplest aldehyde. Formaldehyde also exists as the cyclic trimer trioxane and the polymer paraformaldehyde. It exists in water as the hydrate H2C(OH)2. Aqueous solutions of formaldehyde are referred to as formalin. "100%" formalin consists of a saturated solution of (H2C=O) is dissolved in water Water is the most abundant molecule on Earth's surface, constituting about 75% of the Earth's surface.[citation needed] In nature it exists in liquid, solid, and gaseous states. It is in dynamic equilibrium between the liquid and gas states at standard temperature and pressure. At room temperature, it is a nearly colorless with a hint of blue, the geminal diol (H2C(OH)2), methanediol, is favored. Other examples are the cyclic geminal diols decahydroxycyclopentane Decahydroxycyclopentane is an organic compound with formula C5O10H10 or C510. It is a five-fold geminal diol on a cyclopentane backbone (C5(OH)10) and dodecahydroxycyclohexane Dodecahydroxycyclohexane is an organic compound with molecular formula C6O12H12 or C612. It is a six-fold geminal diol with a cyclohexane backbone and can be regarded as a six-fold hydrate of hexaketocyclohexane (C6O6) (C6(OH)12), which are stable, whereas the corresponding oxocarbons The simplest and most common oxocarbons are carbon monoxide and carbon dioxide (CO2). There are however many other stable or metastable oxides of carbon which rarely occur outside chemical plants and laboratories, such as carbon suboxide (O=C=C=C=O), and mellitic anhydride(C12O9) (C5O5 and C6O6) do not seem to be.
Examples of diols in which the hydroxyl functional groups are more widely separated include 1,4-butanediol 1,4-Butanediol is the organic compound with the formula HOCH2CH2CH2CH2OH. This colorless viscous liquid is derived from butane by placement of alcohol groups at each end of the chain. It is one of four stable isomers of butanediol and bisphenol A Bisphenol A, commonly abbreviated as BPA, is an organic compound with two phenol functional groups. It is a difunctional building block of several important plastics and plastic additives. With an annual production of 2–3 million metric tonnes, it is an important monomer in the production of polycarbonate.
Synthesis of diols
Because diols are a common functional group In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of. However, its relative reactivity can be arrangement, numerous methods of preparation have been developed.
- Vicinal diols can be produced from the oxidation Redox describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide or the reduction of carbon by hydrogen to yield methane (CH4), or it can be a complex process such as the oxidation of sugar in the human body of alkenes The simplest alkene is ethylene , which has the International Union of Pure and Applied Chemistry (IUPAC) name ethene. Alkenes are also called olefins (an archaic synonym, widely used in the petrochemical industry). Aromatic compounds are often drawn as cyclic alkenes, but their structure and properties are different and they are not considered to, usually with dilute acidic An acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion activity greater than in pure water, i.e. a pH less than 7.0. That approximates the modern definition of Johannes Nicolaus Brønsted and Martin Lowry, who independently defined an acid as a compound which donates a hydrogen potassium permanganate Potassium permanganate is the inorganic chemical compound K , also known as potassium manganate(VII). Using alkaline potassium manganate(VII) produces a colour change from clear deep purple to clear green; acidic potassium manganate(VII) turns clear colourless.
- Osmium tetroxide Osmium tetroxide is the chemical compound with the formula OsO4. The compound is noteworthy for its many uses, despite the rarity of osmium. It also has a number of interesting properties, one being that the solid is volatile can similarly be used to oxidize alkenes to vicinal diols.
- hydrogen peroxide In organisms, hydrogen peroxide is naturally produced as a byproduct of oxygen metabolism; virtually all possess enzymes known as peroxidases, which harmlessly and catalytically decompose low concentrations of hydrogen peroxide to water and oxygen reacts with an alkene to the epoxide An epoxide is a cyclic ether with three ring atoms. This ring approximately defines an equilateral triangle, which makes it highly strained. The strained ring makes epoxides more reactive than other ethers. Simple epoxides are named from the parent compound ethylene oxide or oxirane, such as in chloromethyloxirane. As a functional group epoxides and then by saponification Saponification is the hydrolysis of an ester under basic conditions to form an alcohol and the salt of a carboxylic acid . Saponification is commonly used to refer to the reaction of a metallic alkali (base) with a fat or oil to form soap. Saponifiable substances are those that can be converted into soap to the diol for example in the synthesis of trans-cyclohexanediol batch [2] or by microreactor [3]:
- A chemical reaction called Sharpless asymmetric dihydroxylation Sharpless asymmetric dihydroxylation is the chemical reaction of an alkene with osmium tetroxide in the presence of a chiral quinine ligand to form a vicinal diol can be used to produce chiral Human hands are perhaps the most universally recognized example of chirality: The left hand is a non-superposable mirror image of the right hand; no matter how the two hands are oriented, it is impossible for all the major features of both hands to coincide. This difference in symmetry becomes obvious if someone attempts to shake the right hand of diols from alkenes using an osmate reagent A reagent or reactant is a substance or compound consumed during a chemical reaction. Solvents and catalysts, although they are involved in the reaction, are usually not referred to as reactants and a chiral catalyst Catalysis is the process in which the rate of a chemical reaction is either increased or decreased by means of a chemical substance known as a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. The catalyst may participate in multiple chemical transformations. Catalysts.
- Another method is the Woodward cis-hydroxylation The Woodward cis-hydroxylation is the chemical reaction of alkenes with iodine and silver acetate in wet acetic acid to form cis-diols. The reaction is named after its discoverer, Robert Burns Woodward (cis diol) and the related Prévost reaction The Prévost reaction is chemical reaction in which an alkene is converted by iodine and the silver salt of benzoic acid to a vicinal diol with anti stereochemistry. The reaction was discovered by the French chemist Charles Prévost (anti diol), depicted below, which both use iodine and the silver salt of a carboxylic acid.
- In the Prins reaction The Prins reaction is an organic reaction consisting of an electrophilic addition of an aldehyde or ketone to an alkene or alkyne followed by capture of a nucleophile . The outcome of the reaction depends on reaction conditions . With water and a protic acid such as sulfuric acid as the reaction medium and formaldehyde the reaction product is a 1,3 1,3-diols can be formed in a reaction between an alkene The simplest alkene is ethylene , which has the International Union of Pure and Applied Chemistry (IUPAC) name ethene. Alkenes are also called olefins (an archaic synonym, widely used in the petrochemical industry). Aromatic compounds are often drawn as cyclic alkenes, but their structure and properties are different and they are not considered to and formaldehyde Formaldehyde is a chemical compound with the formula CH2O. It is the simplest aldehyde. Formaldehyde also exists as the cyclic trimer trioxane and the polymer paraformaldehyde. It exists in water as the hydrate H2C(OH)2. Aqueous solutions of formaldehyde are referred to as formalin. "100%" formalin consists of a saturated solution of.
Reactions
- A diol reacts like an alcohol In chemistry, an alcohol is any organic compound in which a hydroxyl group (-O , such as esterification Esterification is the general name for a chemical reaction in which two reactants form an ester as the reaction product. Esters are common in organic chemistry and biological materials, and often have a characteristic pleasant, fruity odor. This leads to their extensive use in the fragrance and flavor industry and ether Ether is a class of organic compounds which contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether" (ethoxyethane, CH3-CH2-O-CH2-CH3) formation.
- Diols such as ethylene glycol Ethylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet tasting liquid are used as co-monomers A monomer is a small molecule that may become chemically bonded to other monomers to form a polymer. The most common natural monomer is glucose, which is linked by glycosidic bonds into polymers such as cellulose and starch, and is over 33% of the weight of all plant matter in polymerization In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains. There are many forms of polymerization and different systems exist to categorize them reactions forming polymers A polymer is a large molecule (macromolecule) composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties including some polyesters Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate . Polyesters include naturally-occurring chemicals, such as in the cutin of plant cuticles, as well as and polyurethanes A polyurethane, commonly abbreviated PU, is any polymer consisting of a chain of organic units joined by urethane links. Polyurethane polymers are formed through step-growth polymerization by reacting a monomer containing at least two isocyanate functional groups with another monomer containing at least two hydroxyl (alcohol) groups in the. A different monomer with two identical functional groups, such as a dioyl dichloride or dioic acid is required to continue the process of polymerization through repeated esterification processes.
- In glycol cleavage, the C-C bond in a vicinal In chemistry vicinal stands for any two functional groups bonded to two adjacent carbon atoms. For example the molecule 2,3-dibromobutane carries two vicinal bromine atoms and 1,3-dibromobutane does not diol is cleaved with formation of ketone or aldehyde functional groups.
- A diol can be converted to cyclic ether with acid catalyst, this is the diol cyclization.
See also
- Alcohols In chemistry, an alcohol is any organic compound in which a hydroxyl group (-O , chemical compounds with one hydroxyl group
- Triols, chemical compounds with three hydroxyl group
- Polyols Polyols are alcohols containing multiple hydroxyl groups. In two technological disciplines the term "polyol" has a special meaning: food science and polymer chemistry, chemical compounds with multiple hydroxyl groups
- Ethylene glycol Ethylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet tasting liquid
- Gem Diols, chemical compounds with two hydroxyl groups on a single carbon atom
References
- ^ March, Jerry Jerry March, Ph.D. was an organic chemist and a professor of chemistry at Adelphi University. Dr. March authored the acclaimed March's Advanced Organic Chemistry text, which is considered to be a pillar of graduate-level organic chemistry texts. The book was prepared in its fifth edition at the time of Dr. March's death. Michael B. Smith, Ph.D., (1985), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (3rd ed.), New York: Wiley, ISBN 0-471-85472-7
- ^ trans-cyclohexanediol Organic Syntheses Organic Syntheses is a scientific journal that since 1921 has provided the chemistry community with annual collections of detailed and checked procedures for the organic synthesis of organic compounds. The journal has a solid reputation because each contribution is independently checked by a group of other chemists, Coll. Vol. 3, p.217 (1955); Vol. 28, p.35 (1948) http://www.orgsynth.org/orgsyn/pdfs/CV3P0217.pdf.
- ^ Advantages of Synthesizing trans-1,2-Cyclohexanediol in a Continuous Flow Microreactor over a Standard Glass Apparatus Andreas Hartung, Mark A. Keane, and Arno Kraft J. Org. Chem. The Journal of Organic Chemistry is a scientific journal for original contributions of fundamental research in organic and bioorganic chemistry. It is published by the American Chemical Society. The impact factor of this journal is 3.959 (2007) 2007, 72, 10235-10238 doi The Digital Object Identifier System is a managed system for persistent identification of content-related entities on digital networks . These entities may be content items (digital files, physical objects, abstract works), or any related entities in a content transaction (e.g. licenses, parties, etc.). "DOI" is sometimes used to mean:10.1021/jo701758p
Categories: Functional groups | Polyols
|
Mian Muhammad Tariq
2008-01-23 17:41:00
ContraindicatioNS Hypersensitivity to acetic acid, propylene . glycol. , hydrocortisone, or any component of the formulation; perforated tympanic membrane; herpes simplex; vaccinia, and varicella. drug interactions hydrocortisone: . ...
Q. My sons Chemistry ?
Asked by blues - Mon May 11 19:33:05 2009 - - 4 Answers - 0 Comments
A. Quick answer you don't need it at all if you use an anti-corrosion additive. The problem arises when it may freeze early do to an early frost in the Fall or a late frost in the spring. Antifreeze contains additives to prevent rust and corrosion and lowers the freeze point of the coolant. Here's a little fact to dump in the lap of your son's Chemistry teacher: No matter what the percentage of antifreeze in a cooling system, it acts as an insulator of heat transfer. The motor can't transfer heat to the coolant or get rid of it as quickly through the radiator core as efficiently as *plain water. That's a fact! If antifreeze helped to keep racing engines cooler every one and their brother would be using it. The fact is, nobody does.
Answered by Country Boy - Mon May 11 19:57:07 2009
