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Cucurbituril
In host-guest chemistry, cucurbiturils are macrocyclic molecules made of glycoluril () monomers linked by methylene bridges (). The oxygen atoms are located along the edges of the band and are tilted inwards, forming a partly enclosed cavity ( cavitand). The name is derived from the resemblance of this molecule with a pumpkin of the family of Cucurbitaceae. Cucurbiturils are commonly written as cucurbit 'n''ril, where ''n'' is the number of glycoluril units. Two common abbreviations are CB 'n'''', or simply CB''n''. These compounds are particularly interesting to chemists because they are suitable hosts for an array of neutral and cationic species. The binding mode is thought to occur through hydrophobic interactions, and, in the case of cationic guests, through cation-dipole interactions as well. The dimensions of cucurbiturils are generally on the ~10 Å size scale. For instance, the cavity of cucurbit ril has a height ~9.1 Å, an outer diameter ~5.8 Å, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cucurbituril Gyroscope AngewChemIntEd 2002 V41 P275 Hires
In host-guest chemistry, cucurbiturils are macrocyclic molecules made of glycoluril () monomers linked by methylene bridges (). The oxygen atoms are located along the edges of the band and are tilted inwards, forming a partly enclosed cavity ( cavitand). The name is derived from the resemblance of this molecule with a pumpkin of the family of Cucurbitaceae. Cucurbiturils are commonly written as cucurbit 'n''ril, where ''n'' is the number of glycoluril units. Two common abbreviations are CB 'n'''', or simply CB''n''. These compounds are particularly interesting to chemists because they are suitable hosts for an array of neutral and cationic species. The binding mode is thought to occur through hydrophobic interactions, and, in the case of cationic guests, through cation-dipole interactions as well. The dimensions of cucurbiturils are generally on the ~10 Å size scale. For instance, the cavity of cucurbit ril has a height ~9.1 Å, an outer diameter ~5.8 Å, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kim Kimoon
Kim Kimoon (born 1954) is a South Korean chemist and professor in the Department of Chemistry at Pohang University of Science and Technology (POSTECH). He is the first and current director of the Center for Self-assembly and Complexity at the Institute for Basic Science. Kim has authored or coauthored 300 papers which have been cited more than 30,000 times and he holds a number of patents. His work has been published in ''Nature'', ''Nature Chemistry'', ''Angewandte Chemie'', and '' JACS'', among others. He has been a Clarivate Analytics Highly Cited Researcher in the field of chemistry in 2014, 2015, 2016. His research has focused on developing novel functional materials and devices based on supramolecular chemistry. In particular, his research group has worked on a various functional materials based on cucurbiturils (CB ), pumpkin-shaped macrocyclic molecules, and metal-organic porous materials for catalysis, separation, and gas storage. His discovery and isolation of new members ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cavitand
In chemistry, a cavitand is a container-shaped molecule. The cavity of the cavitand allows it to engage in host–guest chemistry with guest molecules of a complementary shape and size. The original definition proposed by Cram includes many classes of molecules: cyclodextrins, calixarenes, pillararenes and cucurbiturils. However, modern usage in the field of supramolecular chemistry specifically refers to cavitands formed on a resorcinarene scaffold by bridging adjacent phenolic units. The simplest bridging unit is methylene (), although dimethylene (), trimethylene (), benzal, xylyl, pyridal, 2,3-disubstituted-quinoxaline, ''o''-dinitrobenzyl, dialkylsilydine, and phosphonates are known. Cavitands that have an extended aromatic bridging unit, or an extended cavity containing 3 rows of aromatic rings are referred to as deep-cavity cavitands and have broad applications in host-guest chemistry. These types of cavitands were extensively investigated by Rebek, and Gibb, am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inclusion Compound
In host–guest chemistry In supramolecular chemistry, host–guest chemistry describes complexes that are composed of two or more molecules or ions that are held together in unique structural relationships by forces other than those of full covalent bonds. Host–guest ch ..., an inclusion compound (also known as an inclusion complex) is a chemical complex in which one chemical compound (the "host") has a cavity into which a "guest" compound can be accommodated. The interaction between the host and guest involves purely van der Waals bonding. The definition of inclusion compounds is very broad, extending to channels formed between molecules in a crystal lattice in which guest molecules can fit. Examples and case studies Calixarenes Calixarenes and related formaldehyde-arene condensates are one class of hosts that form inclusion compounds. One famous illustration is the adduct with cyclobutadiene, which otherwise is unstable. Cyclodextrins Cyclodextrins are well establ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robert Behrend
Anton Friedrich Robert Behrend (17 December 1856 – 15 September 1926) was a German analytical organic chemist who made pioneering studies of stereochemistry and isomerism. He was also the first to synthesize uric acid and introduced potentiometric titration. The Behrend rearrangement reaction of nitrones is named after him. Behrend was born in Harburg to Karl, a trader and his wife Louise Elisabeth Margarethe Carol née Himbeck. He grew up in Hamburg. He joined the infantry regiment in 1876 and studied law for some time and then shifted to physics under Emil Gabriel Warburg. In 1877-78 he tried to study chemistry at Leipzig under Herman Kolbe but was not accepted as he knew nothing. He then worked under Gustav Heinrich Wiedemann and received a doctorate in organic chemistry in 1881. He became a professor in 1889 and in 1897, he moved to the Technical College of Hannover working on stereochemistry. He was among the first to synthesize uric acid, and cucurbituril In host-g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glycoluril
Glycoluril is an organic chemical composed of two cyclic urea groups joined across the same two-carbon chain. It is a white powder that has been used in water treatment, in paints and coatings, and occasionally as a slow-release fertilizer. Production Glycoluril can be synthesized by reacting two equivalents of urea with glyoxal. Likewise, using other vicinal carbonyl (or carbonyl hydrate) reactants give derivatives having various functional groups in place of the hydrogen atoms on the carbon chain. Properties The four amide-like and therefore acidic hydrogen atoms of glycoluril are amenable to a variety of chemical reactions, such as substitution with halogen atoms or a reaction with formaldehyde. Use Glycouril itself and derivatives of it are used as monomers for producing the macrocyclic cucurbiturils polymers, which serve as hosts to bind to various neutral and cationic species. They are also used in several classes of non-cyclic structures that also bind a variety of st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pillararene
Pillararenes are macrocycles composed of hydroquinone or dialkoxybenzene units (5 to 10) linked in the para position by methylene bridges. They are structurally similar to the cucurbiturils and calixarenes that play an important part in host–guest chemistry. The first pillararene was the five membered dimethoxypillar rene. History 1,4-Dimethoxypillar rene, the first pillararene, was reported in 2008 by Tomoki Ogoshi ''et al.'' They catalyzed the condensation of 1,4-dimethoxybenzene and paraformaldehyde using a Lewis acid to obtain 1,4-dimethoxypillar rene (DMpillar rene). The methoxy groups of DMpillar rene were then deprotected using boron tribromide and removed to give pillar rene. Ogoshi and Kanai decided naming the new family of host macrocycles "pillararene", since they are cylindrical or pillar-like in shape and composed of aromatic or "arene" moieties.1 Chemists often refer to them as "pillarenes" orally as this is easier to pronounce and remember. It is pertinent to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aminal
In organic chemistry, an aminal or aminoacetal is a functional group or type of organic compound that has two amine groups attached to the same carbon atom: . (As is customary in organic chemistry, R can represent hydrogen or an alkyl group). A common aminal is bis(dimethylamino)methane, a colorless liquid that is prepared by the reaction of dimethylamine and formaldehyde: : 2 (CH3)2NH + CH2O -> CH3)2NCH2 + H2O Aminals are encountered in, for instance, the Fischer indole synthesis. Several examples exist in nature. Physostigmin.svg, Physostigmine,a highly toxic cholinesterase inhibitor found in the Calabar bean. Hodgkinsine.png, Hodgkinsine, an alkaloid with antiviral, antibacterial and antifungal effects 5,10-methylenetetrahydrofolic acid.svg, 5,10-Methylenetetrahydrofolate, an intermediate in one-carbon metabolism Hexahydro-1,3,5-triazine (), an intermediate in the condensation of formaldehyde and ammonia, tends to degrade to hexamethylene tetraamine. Cyclic am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Urea
Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important role in the metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals. It is a colorless, odorless solid, highly soluble in water, and practically non-toxic ( is 15 g/kg for rats). Dissolved in water, it is neither acidic nor alkaline. The body uses it in many processes, most notably nitrogen excretion. The liver forms it by combining two ammonia molecules () with a carbon dioxide () molecule in the urea cycle. Urea is widely used in fertilizers as a source of nitrogen (N) and is an important raw material for the chemical industry. In 1828 Friedrich Wöhler discovered that urea can be produced from inorganic starting materials, which was an important conceptual miles ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dialdehyde
In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group. Aldehydes are common and play important roles in the technology and biological spheres. Structure and bonding Aldehydes feature a carbon center that is connected by a double bond to oxygen and a single bond to hydrogen and single bond to a third substituent, which is carbon or, in the case of formaldehyde, hydrogen. The central carbon is often described as being sp2- hybridized. The aldehyde group is somewhat polar. The C=O bond length is about 120-122 picometers. Physical properties and characterization Aldehydes have properties that are diverse and that depend on the remainder of the molecule. Smaller aldehydes are more soluble in water, formaldehyde and acetaldehyde completely so. The volatile aldehydes have pungent odors. Aldehy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glyoxal
Glyoxal is an organic compound with the chemical formula OCHCHO. It is the smallest dialdehyde (a compound with two aldehyde groups). It is a crystalline solid, white at low temperatures and yellow near the melting point (15 °C). The liquid is yellow, and the vapor is green.O'Neil, M.J. (2001): ''The Merck Index'', 13th Edition, page 803. Pure glyoxal is not commonly encountered because glyoxal is usually handled as a 40% aqueous solution (density near 1.24 g/mL). It forms a series of hydrates, including oligomers. For many purposes, these hydrated oligomers behave equivalently to glyoxal. Glyoxal is produced industrially as a precursor to many products. Production Glyoxal was first prepared and named by the German-British chemist Heinrich Debus (1824–1915) by reacting ethanol with nitric acid. Commercial glyoxal is prepared either by the gas-phase oxidation of ethylene glycol in the presence of a silver or copper catalyst (the Laporte process) or by the li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Condensation Reaction
In organic chemistry, a condensation reaction is a type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a dehydration synthesis. However other molecules can also be lost, such as ammonia, ethanol, acetic acid and hydrogen sulfide. The addition of the two molecules typically proceeds in a step-wise fashion to the addition product, usually in equilibrium, and with loss of a water molecule (hence the name condensation). The reaction may otherwise involve the functional groups of the molecule, and is a versatile class of reactions that can occur in acidic or basic conditions or in the presence of a catalyst. This class of reactions is a vital part of life as it is essential to the formation of peptide bonds between amino acids and to the biosynthesis of fatty acids. Many variations of condensation reactions exist. Common examples include the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
