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Decarboxylation
Decarboxylation is a chemical reaction that removes a carboxyl group and releases carbon dioxide (CO2). Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is the first chemical step in photosynthesis, is called carboxylation, the addition of CO2 to a compound. Enzymes that catalyze decarboxylations are called decarboxylases or, the more formal term, carboxy-lyases (Enzyme Commission number, EC number 4.1.1). In organic chemistry The term "decarboxylation" usually means replacement of a carboxyl group () with a hydrogen atom: : Decarboxylation is one of the oldest known organic reactions. It is one of the processes assumed to accompany pyrolysis and destructive distillation. Overall, decarboxylation depends upon stability of the carbanion synthon , although the anion may not be a true chemical intermediate. Typically, carboxylic acids decarboxylate slowly, but carboxylic acids with an α el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ketonization
Ketonic decarboxylation (also known as decarboxylative ketonization) is a type of organic reaction involving decarboxylation, converting two equivalents of a carboxylic acid () to a symmetric ketone (). The reaction typically requires heat and a metal catalyst, and generally proceeds in low yields. It can be thought of as a decarboxylative Claisen condensation. Water and carbon dioxide are byproducts: : Bases promote this reaction. The reaction mechanism is proposed to involve nucleophilic attack of the alpha-carbon of one acid group on the other carboxylic acid group, possibly as a concerted reaction with the decarboxylation. The initial formation of an intermediate carbanion via decarboxylation of one of the acid groups prior to the nucleophilic attack is unlikely since the byproduct resulting from the carbanion's protonation by the acid has not been reported. This reaction is different from oxidative decarboxylation, which proceeds through a radical mechanism and is characte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decarboxylase
Carboxy-lyases, also known as decarboxylases, are carbon–carbon lyases that add or remove a carboxyl group from organic compounds. These enzymes catalyze the decarboxylation of amino acids and alpha-keto acids. Classification and nomenclature Carboxy-lyases are categorized under EC number 4.1.1. Usually, they are named after the substrate whose decarboxylation they catalyze, for example pyruvate decarboxylase catalyzes the decarboxylation of pyruvate. Examples * Aromatic-L-amino-acid decarboxylase * Glutamate decarboxylase * Histidine decarboxylase * Ornithine decarboxylase * Phosphoenolpyruvate carboxylase * Pyruvate decarboxylase * RuBisCO – the only carboxylase that leads to a net fixation of carbon dioxide * Uridine monophosphate synthetase * Uroporphyrinogen III decarboxylase * enoyl-CoA carboxylases/reductases (ECRs) See also * Enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboxy-lyases
Carboxy-lyases, also known as decarboxylases, are carbon–carbon lyases that add or remove a carboxyl group from organic compounds. These enzymes catalyze the decarboxylation of amino acids and alpha-keto acids. Classification and nomenclature Carboxy-lyases are categorized under EC number 4.1.1. Usually, they are named after the substrate whose decarboxylation they catalyze, for example pyruvate decarboxylase catalyzes the decarboxylation of pyruvate. Examples * Aromatic-L-amino-acid decarboxylase * Glutamate decarboxylase * Histidine decarboxylase * Ornithine decarboxylase * Phosphoenolpyruvate carboxylase * Pyruvate decarboxylase * RuBisCO – the only carboxylase that leads to a net fixation of carbon dioxide * Uridine monophosphate synthetase * Uroporphyrinogen III decarboxylase * enoyl-CoA carboxylases/reductases (ECRs) See also * Enzymes * Lyase In biochemistry, a lyase is an enzyme that catalyzes the breaking (an elimination reaction) of various chemical bonds b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboxyl Group
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl group (e.g., alkyl, alkenyl, aryl), or hydrogen, or other groups. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion. Examples and nomenclature Carboxylic acids are commonly identified by their trivial names. They often have the suffix ''-ic acid''. IUPAC-recommended names also exist; in this system, carboxylic acids have an ''-oic acid'' suffix. For example, butyric acid () is butanoic acid by IUPAC guidelines. For nomenclature of complex molecules containing a carboxylic acid, the carboxyl can be considered position one of the parent chain even if there are other substituents, such as 3-chloropropanoic acid. Alternately, it can be named as a " ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ketone
In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone (where R and R' are methyl), with the formula . Many ketones are of great importance in biology and 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 considered retained IUPAC names, although some introdu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboxylic Acids
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl group (e.g., alkyl, alkenyl, aryl), or hydrogen, or other groups. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion. Examples and nomenclature Carboxylic acids are commonly identified by their trivial names. They often have the suffix ''-ic acid''. IUPAC-recommended names also exist; in this system, carboxylic acids have an ''-oic acid'' suffix. For example, butyric acid () is butanoic acid by IUPAC guidelines. For nomenclature of complex molecules containing a carboxylic acid, the carboxyl can be considered position one of the parent chain even if there are other substituents, such as 3-chloropropanoic acid. Alternately, it can be named ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzoic Acid
Benzoic acid () is a white (or colorless) solid organic compound with the formula , whose structure consists of a benzene ring () with a carboxyl () substituent. The benzoyl group is often abbreviated "Bz" (not to be confused with "Bn," which is used for benzyl), thus benzoic acid is also denoted as BzOH, since the benzoyl group has the formula –. It is the simplest aromatic carboxylic acid. The name is derived from gum benzoin, which was for a long time its only source. Benzoic acid occurs naturally in many plants and serves as an intermediate in the biosynthesis of many secondary metabolites. Salts of benzoic acid are used as food preservatives. Benzoic acid is an important precursor for the industrial synthesis of many other organic substances. The salts and esters of benzoic acid are known as benzoates (). History Benzoic acid was discovered in the sixteenth century. The dry distillation of gum benzoin was first described by Nostradamus (1556), and then by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitro Compound
In organic chemistry, nitro compounds are organic compounds that contain one or more nitro functional groups (). The nitro group is one of the most common explosophores (functional group that makes a compound explosive) used globally. The nitro group is also strongly electron-withdrawing. Because of this property, bonds alpha (adjacent) to the nitro group can be acidic. For similar reasons, the presence of nitro groups in aromatic compounds retards electrophilic aromatic substitution but facilitates nucleophilic aromatic substitution. Nitro groups are rarely found in nature. They are almost invariably produced by nitration reactions starting with nitric acid. Synthesis Preparation of aromatic nitro compounds Aromatic nitro compounds are typically synthesized by nitration. Nitration is achieved using a mixture of nitric acid and sulfuric acid, which produce the nitronium ion (), which is the electrophile: + The nitration product produced on the largest scale, by f ... [...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 forms: * 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Malonic Ester Synthesis
The malonic ester synthesis is a chemical reaction where diethyl malonate or another ester of malonic acid is alkylated at the carbon alpha (directly adjacent) to both carbonyl groups, and then converted to a substituted acetic acid. A major drawback of malonic ester synthesis is that the alkylation stage can also produce dialkylated structures. This makes separation of products difficult and yields lower. Mechanism The carbons alpha to carbonyl groups can be deprotonated by a strong base. The carbanion formed can undergo nucleophilic substitution on the alkyl halide, to give the alkylated compound. On heating, the di-ester undergoes thermal decarboxylation, yielding an acetic acid substituted by the appropriate R group. Thus, the malonic ester can be thought of being equivalent to the −CH2COOH synthon. The esters chosen are usually the same as the base used, i.e. ethyl esters with sodium ethoxide. This is to prevent scrambling by transesterification. Variations Dialky ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Chlorodifluoroacetate
Sodium chlorodifluoroacetate is the organofluorine compound with the formula . It is a salt formed by neutralization of chlorodifluoroacetic acid with sodium hydroxide. The compound, a white solid, is of interest as a source of difluorocarbene: : This reaction is conducted in a hot solution also containing the substrate. Diglyme is a typical solvent. The conversion of sodium chlorodifluoroacetate is proposed to start with decarboxylation, which generates the carbanion . One set of applications is difluorocyclopropanation In organic chemistry, cyclopropanation refers to any chemical process which generates cyclopropane () Ring (chemistry), rings. It is an important process in modern chemistry as many useful compounds bear this motif; for example pyrethroid insectic .... Thermal decomposition of sodium chlorodifluoroacetate in the presence of triphenylphosphine and an aldehyde allows for a Wittig-like reactions In this case, {{chem2, (C6H5)3P\dCF2 is proposed as an intermedia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
