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Malonodinitrile
Malononitrile is an organic compound nitrile with the formula . It is a colorless or white solid. It can be prepared by dehydration of cyanoacetamide. Malononitrile is relatively acidic, with a p''K''a of 11 in water. This allows it to be used in the Knoevenagel condensation, for example in the preparation of CS gas: Malononitrile is a suitable starting material for the Gewald reaction, where the nitrile condenses with a ketone or aldehyde in the presence of elemental sulfur and a base to produce a 2-aminothiophene Thiophene is a heterocyclic compound with the formula C4H4S. Consisting of a planar five-membered ring, it is aromatic as indicated by its extensive substitution reactions. It is a colorless liquid with a benzene-like odor. In most of its reacti .... See also * Malonic acid * Diethyl malonate References External links WebBook page for C3H2N2 {{Authority control Alkanedinitriles ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ball-and-stick Model
In chemistry, the ball-and-stick model is a molecular model of a chemical substance which displays both the three-dimensional position of the atoms and the bonds between them. The atoms are typically represented by spheres, connected by rods which represent the bonds. Double and triple bonds are usually represented by two or three curved rods, respectively, or alternately by correctly positioned sticks for the sigma and pi bonds. In a good model, the angles between the rods should be the same as the angles between the bonds, and the distances between the centers of the spheres should be proportional to the distances between the corresponding atomic nuclei. The chemical element of each atom is often indicated by the sphere's color. In a ball-and-stick model, the radius of the spheres is usually much smaller than the rod lengths, in order to provide a clearer view of the atoms and bonds throughout the model. As a consequence, the model does not provide a clear insight about th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The study of the properties, reactions, and syntheses of organic compounds comprise the discipline known as organic chemistry. For historical reasons, a few classes of carbon-containing compounds (e.g., carbonate salts and cyanide salts), along with a few other exceptions (e.g., carbon dioxide, hydrogen cyanide), are not classified as organic compounds and are considered inorganic. Other than those just named, little consensus exists among chemists on precisely which carbon-containing compounds are excluded, making any rigorous definition of an organic compound elusive. Although organic compounds make up only a small percentage of Earth's crust, they are of central importance because all known life is based on organic compounds. Living t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Malonic Acid
Malonic acid (IUPAC systematic name: propanedioic acid) is a dicarboxylic acid with structure CH2(COOH)2. The ionized form of malonic acid, as well as its esters and salts, are known as malonates. For example, diethyl malonate is malonic acid's diethyl ester. The name originates from the Greek word μᾶλον (''malon'') meaning 'apple'. History Malonic acid is a naturally occurring substance found in many fruits and vegetables. There is a suggestion that citrus fruits produced in organic farming contain higher levels of malonic acid than fruits produced in conventional agriculture. Malonic acid was first prepared in 1858 by the French chemist Victor Dessaignes via the oxidation of malic acid. Structure and preparation The structure has been determined by X-ray crystallography and extensive property data including for condensed phase thermochemistry are available from the National Institute of Standards and Technology. A classical preparation of malonic acid starts from chlor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thiophene
Thiophene is a heterocyclic compound with the formula C4H4S. Consisting of a planar five-membered ring, it is aromatic as indicated by its extensive substitution reactions. It is a colorless liquid with a benzene-like odor. In most of its reactions, it resembles benzene. Compounds analogous to thiophene include furan (C4H4O), selenophene (C4H4Se) and pyrrole (C4H4NH), which each vary by the heteroatom in the ring. Isolation and occurrence Thiophene was discovered as a contaminant in benzene. It was observed that isatin (an indole) forms a blue dye if it is mixed with sulfuric acid and crude benzene. The formation of the blue indophenin had long been believed to be a reaction of benzene itself. Viktor Meyer was able to isolate thiophene as the actual substance responsible for this reaction. Thiophene and especially its derivatives occur in petroleum, sometimes in concentrations up to 1–3%. The thiophenic content of oil and coal is removed via the hydrodesulfurization (HDS) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula S8. Elemental sulfur is a bright yellow, crystalline solid at room temperature. Sulfur is the tenth most abundant element by mass in the universe and the fifth most on Earth. Though sometimes found in pure, native form, sulfur on Earth usually occurs as sulfide and sulfate minerals. Being abundant in native form, sulfur was known in ancient times, being mentioned for its uses in ancient India, ancient Greece, China, and ancient Egypt. Historically and in literature sulfur is also called brimstone, which means "burning stone". Today, almost all elemental sulfur is produced as a byproduct of removing sulfur-containing contaminants from natural gas and petroleum.. Downloahere The greatest commercial use of the element is the production o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aldehyde
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. Al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bond C=O). The simplest ketone is acetone (where R and R' is methyl), with the formula . Many ketones are of great importance in biology and in industry. Examples include many sugars (ketoses), many steroids (e.g., testosterone), and the solvent acetone. Nomenclature and etymology The word ''ketone'' is derived from ''Aketon'', an old German word for ''acetone''. According to the rules of IUPAC nomenclature, ketone names are derived by changing the suffix ''-ane'' of the parent alkane to ''-anone''. Typically, the position of the carbonyl group is denoted by a number, but traditional nonsystematic names are still generally used for the most important ketones, for example acetone and benzophenone. These nonsystematic names are considere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gewald Reaction
The Gewald reaction is an organic reaction involving the condensation of a ketone (or aldehyde when R2 = H) with a α-cyanoester in the presence of elemental sulfur and base to give a poly-substituted 2-amino-thiophene. The reaction is named after the German chemist Karl Gewald (born 1930).John A. Joule, Keith Mills: ''Heterocyclic Chemistry'', John Wiley & Sons, 5. Auflage (2010), p. 340, .Bradford P. Mundy, Michael G. Ellerd, Frank G. Favaloro, Jr.: ''Name Reactions and Reagents in Organic Synthesis'', John Wiley & Sons, 2. Auflage (2005) p. 306, .Christopher Hume: ''Applications of Multicomponent Reactions in Drug Discovery – Lead Generation to Process Development'', p. 311−341, see p. 332−334, In Jieping Zhu, Huges Bienaymé: ''Multicomponent Reactions'', Wiles-VCH Verlag, 2005, . Reaction mechanism The reaction mechanism of the Gewald reaction was elucidated 30 years after the reaction was discovered. The first step is a Knoevenagel condensation between the keton ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CS Gas
The compound 2-chlorobenzalmalononitrile (also called ''o''-chlorobenzylidene malononitrile; chemical formula: C10H5ClN2), a cyanocarbon, is the defining component of tear gas commonly referred to as CS gas, which is used as a riot control agent. Exposure causes a burning sensation and tearing of the eyes to the extent that the subject cannot keep their eyes open, and a burning irritation of the mucous membranes of the nose, mouth and throat, resulting in profuse coughing, nasal mucus discharge, disorientation, and difficulty breathing, partially incapacitating the subject. CS gas is an aerosol of a volatile solvent (a substance that dissolves other active substances and that easily evaporates) and 2-chlorobenzalmalononitrile, which is a solid compound at room temperature. CS gas is generally accepted as being non-lethal. It was first synthesized by two Americans, Ben Corson and Roger Stoughton, at Middlebury College in 1928, and the chemical's name is derived from the firs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Knoevenagel Condensation
In organic chemistry, the Knoevenagel condensation () reaction is a type of chemical reaction named after German chemist Emil Knoevenagel. It is a modification of the aldol condensation. A Knoevenagel condensation is a nucleophilic addition of an active hydrogen compound to a carbonyl group followed by a dehydration reaction in which a molecule of water is eliminated (hence ''condensation''). The product is often an α,β-unsaturated ketone (a conjugated enone). In this reaction the carbonyl group is an aldehyde or a ketone. The catalyst is usually a weakly basic amine. The active hydrogen component has the form * or for instance diethyl malonate, Meldrum's acid, ethyl acetoacetate or malonic acid, or cyanoacetic acid. * , for instance nitromethane. where Z is an electron withdrawing group. Z must be powerful enough to facilitate deprotonation to the enolate ion even with a mild base. Using a strong base in this reaction would induce self-condensation of the aldehyde o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acid Dissociation Constant
In chemistry, an acid dissociation constant (also known as acidity constant, or acid-ionization constant; denoted ) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction :HA A^- + H^+ known as dissociation in the context of acid–base reactions. The chemical species HA is an acid that dissociates into , the conjugate base of the acid and a hydrogen ion, . The system is said to be in equilibrium when the concentrations of its components will not change over time, because both forward and backward reactions are occurring at the same rate. The dissociation constant is defined by :K_\text = \mathrm, or :\mathrmK_\ce = - \log_ K_\text = \log_\frac where quantities in square brackets represent the concentrations of the species at equilibrium. Theoretical background The acid dissociation constant for an acid is a direct consequence of the underlying thermodynamics of the dissociation reaction; the p''K''a v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
