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Aza-crown Ether
In organic chemistry, an aza-crown ether is an aza analogue of a crown ether (cyclic polyether). That is, it has a nitrogen atom (amine linkage, or ) in place of each oxygen atom (ether linkage, ) around the ring. While the parent crown ethers have the formulae , the parent ''aza''-crown ethers have the formulae , where n = 3, 4, 5, 6. Well-studied aza crowns include triazacyclononane (n = 3), cyclen (n = 4), and hexaaza-18-crown-6 (n = 6). File:Me3TACN.png, 1,4,7-Trimethyl-1,4,7-triazacyclononane, a tridentate ligand used in coordination chemistry. File:Cyclam.png, Cyclam is a tetraaza crown ether with alternating and linkers between amine centers. File:Plerixafor.svg, Plerixafor, a derivative of cyclam, is used to treat lymphoma and multiple myeloma. File:Cryptand.svg, 2.2.2-Cryptand is an aza-crown of the mixed ether-amine variety. Synthesis The synthesis of aza crown ethers are subject to the challenges associated with the preparation of macrocycles. The 18-membered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lymphoma
Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enlarged lymph nodes, fever, drenching sweats, unintended weight loss, itching, and constantly feeling tired. The enlarged lymph nodes are usually painless. The sweats are most common at night. Many subtypes of lymphomas are known. The two main categories of lymphomas are the non-Hodgkin lymphoma (NHL) (90% of cases) and Hodgkin lymphoma (HL) (10%). The World Health Organization (WHO) includes two other categories as types of lymphoma – multiple myeloma and immunoproliferative diseases. Lymphomas and leukemias are a part of the broader group of tumors of the hematopoietic and lymphoid tissues. Risk factors for Hodgkin lymphoma include infection with Epstein–Barr virus and a history of the disease in the family. Risk factors for common ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secondary Amines
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group (these may respectively be called alkylamines and arylamines; amines in which both types of substituent are attached to one nitrogen atom may be called alkylarylamines). Important amines include amino acids, biogenic amines, trimethylamine, and aniline; Inorganic derivatives of ammonia are also called amines, such as monochloramine (). The substituent is called an amino group. Compounds with a nitrogen atom attached to a carbonyl group, thus having the structure , are called amides and have different chemical properties from amines. Classification of amines Amines can be classified according to the nature and number of substituents on nitrogen. Aliphatic amines contain only H and alkyl substituents. Aromatic a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyamines
A polyamine is an organic compound having more than two amino groups. Alkyl polyamines occur naturally, but some are synthetic. Alkylpolyamines are colorless, hygroscopic, and water soluble. Near neutral pH, they exist as the ammonium derivatives. Most aromatic polyamines are crystalline solids at room temperature. Natural polyamines Low-molecular-weight linear polyamines are found in all forms of life. The principal examples are the triamine spermidine and the tetraamine spermine. They are structurally and biosynthetically related to the diamines putrescine and cadaverine. Polyamine metabolism is regulated by the activity of the enzyme ornithine decarboxylase (ODC). Polyamines are found in high concentrations in the mammalian brain. File:Spermidine-2D-skeletal.svg, spermidine File:Spermine.svg, spermine Synthetic polyamines Several synthetic polyamines are used in chemical industry and the research laboratory. They are mainly of interest as additives to motor oil and as co-rea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lariat
A lasso ( or ), also called lariat, riata, or reata (all from Castilian, la reata 're-tied rope'), is a loop of rope designed as a restraint to be thrown around a target and tightened when pulled. It is a well-known tool of the Spanish and Mexican cowboy, then adopted by the cowboys of the United States. The word is also a verb; ''to lasso'' is to throw the loop of rope around something. Overview A lasso is made from stiff rope so that the noose stays open when the lasso is thrown. It also allows the cowboy to easily open up the noose from horseback to release the cattle because the rope is stiff enough to be pushed a little. A high quality lasso is weighted for better handling. The lariat has a small reinforced loop at one end, called a ''honda'' or ''hondo'', through which the rope passes to form a loop. The ''honda'' can be formed by a honda knot (or another loop knot), an eye splice, a seizing, rawhide, or a metal ring. The other end is sometimes tied simply in a sm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryptand
In chemistry, cryptands are a family of synthetic, bicyclic and polycyclic, multidentate ligands for a variety of cations. The Nobel Prize for Chemistry in 1987 was given to Donald J. Cram, Jean-Marie Lehn, and Charles J. Pedersen for their efforts in discovering and determining uses of cryptands and crown ethers, thus launching the now flourishing field of supramolecular chemistry. The term ''cryptand'' implies that this ligand binds substrates in a crypt, interring the guest as in a burial. These molecules are three-dimensional analogues of crown ethers but are more selective and strong as complexes for the guest ions. The resulting complexes are lipophilic. Structure The most common and most important cryptand is ; the systematic IUPAC name for this compound is 1,10-diaza-4,7,13,16,21,24-hexaoxabicyclo .8.8exacosane. This compound is termed .2.2ryptand, where the numbers indicate the number of ether oxygen atoms (and hence binding sites) in each of the three bridges be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trimethyltriazacyclononane
1,4,7-Trimethyl-1,4,7-triazacyclononane is the aza-crown ether with the formula (CH2CH2NCH3)3. This colorless liquid is the N-methylated derivative of triazacyclononane (TACN), a face-capping tridentate ligand that is popular in coordination chemistry A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many .... Although TACN is known for forming 2:1 "sandwich" complexes with many metal ions, corresponding 2:1 complexes of Me3TACN are only known for Ag+, Na+, and K+. This effect is mainly due to the greater bulk of Me3TACN, which requires ions with a larger ionic radius to accommodate two ligands. Several related derivatives have been prepared with diverse substituents on nitrogen. References {{DEFAULTSORT:Trimethyl-1,4,7-triazacyclononane, 1,4,7- Polyamines Chelating agents Mac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tertiary Amine
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group (these may respectively be called alkylamines and arylamines; amines in which both types of substituent are attached to one nitrogen atom may be called alkylarylamines). Important amines include amino acids, biogenic amines, trimethylamine, and aniline; Inorganic derivatives of ammonia are also called amines, such as monochloramine (). The substituent is called an amino group. Compounds with a nitrogen atom attached to a carbonyl group, thus having the structure , are called amides and have different chemical properties from amines. Classification of amines Amines can be classified according to the nature and number of substituents on nitrogen. Aliphatic amines contain only H and alkyl substituents. Aromatic a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclam
Cyclam (1,4,8,11-tetraazacyclotetradecane) is an organic compound with the formula (NHCH2CH2NHCH2CH2CH2)2. Classified as an aza-crown ether, it is a white solid that is soluble in water. As a macrocyclic ligand, it binds strongly to many transition metal cations. The compound was first prepared by the reaction of 1,3-dibromopropane and ethylenediamine. The compound features four secondary amines. Its complexes therefore can exist as several diastereomers, depending on the relative orientation of the N–H centres. Its complexes feature alternating five- and six-membered chelate rings. The closely related ligand cyclen ((CH2CH2NH)4) forms only five-membered C2N2M chelate rings and tends not to form square-planar complexes. ''N''-Alkyl derivatives Metal-cyclam complexes are prone to oxidative degradation, which is initiated by deprotonation of the secondary amine. This flaw led to the development of cyclam derivatives wherein the NH centres are replaced by tertiary amines. F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macrocyclization
Macrocycles are often described as molecules and ions containing a ring of twelve or more atoms. Classical examples include the crown ethers, calixarenes, porphyrins, and cyclodextrins. Macrocycles describe a large, mature area of chemistry. Synthesis The formation of macrocycles by ring-closure is called macrocylization. Pioneering work was reported for studies on terpenoid macrocycles. The central challenge to macrocyclization is that ring-closing reactions do not favor the formation of large rings. Instead, small rings or polymers tend to form. This kinetic problem can be addressed by using high-dilution reactions, whereby intramolecular processes are favored relative to polymerizations. Some macrocyclizations are favored using template reactions. Templates are ions, molecules, surfaces etc. that bind and pre-organize compounds, guiding them toward formation of a particular ring size. The crown ethers are often generated in the presence of an alkali metal cation, which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfonamide
In organic chemistry, the sulfonamide functional group (also spelled sulphonamide) is an organosulfur group with the structure . It consists of a sulfonyl group () connected to an amine group (). Relatively speaking this group is unreactive. Because of the rigidity of the functional group, sulfonamides are typically crystalline; for this reason, the formation of a sulfonamide is a classic method to convert an amine into a crystalline derivative which can be identified by its melting point. Many important drugs contain the sulfonamide group. A sulfonamide (compound) is a chemical compound that contains this group. The general formula is or , where each R is some organic group; for example, "methanesulfonamide" (where R = methane, R' = R" = hydrogen) is . Any sulfonamide can be considered as derived from a sulfonic acid by replacing a hydroxyl group () with an amine group. In medicine, the term "sulfonamide" is sometimes used as a synonym for sulfa drug, a derivative or var ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diethylene Triamine
Diethylenetriamine (abbreviated Dien or DETA) and also known as 2,2’-Iminodi(ethylamine)) is an organic compound with the formula HN(CH2CH2NH2)2. This colourless hygroscopic liquid is soluble in water and polar organic solvents, but not simple hydrocarbons. Diethylenetriamine is structural analogue of diethylene glycol. Its chemical properties resemble those for ethylene diamine, and it has similar uses. It is a weak base and its aqueous solution is alkaline. DETA is a byproduct of the production of ethylenediamine from ethylene dichloride. Reactions and uses Diethylenetriamine is a common curing agent for epoxy resins in epoxy adhesives and other thermosets. It is N-alkylated upon reaction with epoxide groups forming crosslinks. In coordination chemistry, it serves as a tridentate ligand forming complexes such as Co(dien)(NO2)3. Like some related amines, it is used in oil industry for the extraction of acid gas. Like ethylenediamine, DETA can also be used to sensitize nitr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
6) (BIGNOU01).png "Click for more on -> Aza-crown Ether")
.jpg "Click for more on -> Lariat")
ML3.png "Click for more on -> Trimethyltriazacyclononane")
Cl2.png "Click for more on -> Cyclam")
