| Pyrrole | |
|---|---|
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| IUPAC name | Pyrrole Pyrrol |
| Identifiers | |
| CAS number | [109-97-7] |
| SMILES | C1=CC=CN1 |
| InChI | 1/C4H5N/c1-2-4-5-3-1/h1-5H |
| Properties | |
| Molecular formula | C4H5N |
| Molar mass | 67. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to The IUPAC International Chemical Identifier ( InChI, pronounced "INchee" is a textual Identifier for Chemical substances designed to provide a A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) 09 g/mol |
| Density | 0. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different 967 g/cm3 |
| Melting point |
−23 °C |
| Boiling point |
129–131 °C |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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Pyrrole, or pyrrol, is a heterocyclic aromatic organic compound, a five-membered ring with the formula C4H4NH. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid In Chemistry, the standard state of a material is its state at 1 bar (100 Kilopascals exactly An organic compound is any member of a large class of Chemical compounds whose Molecules contain Carbon. A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 [1] Substituted derivatives are also called pyrroles. For example, C4H4NCH3 is N-methylpyrrole. Porphobilinogen is a trisubstituted pyrrole, which is the biosynthetic precursor to many natural products. Porphobilinogen (PBG is a Pyrrole involved in Porphyrin metabolism [2]
Pyrroles are components of more complex macrocycles, including the porphyrins of heme, the chlorins and bacteriochlorins[3] of chlorophyll, and porphyrinogens. A porphyrin is a heterocyclic Macrocycle derived from four Pyrroline subunits interconnected via their α carbon atoms via Methine bridges (=CH- A heme ( American English) or haem ( British English) is a Prosthetic group that consists of an Iron atom contained in the center of In Organic chemistry, a chlorin is a large Heterocyclic Aromatic ring consisting at the core of three Pyrroles and one Pyrroline Chlorophyll is a green Pigment found in most Plants Algae and Cyanobacteria.
Contents |
Properties
Pyrrole has very low basicity compared to amines and other aromatic compounds like pyridine, wherin the ring nitrogen is not bonded to a hydrogen atom. Amines are Organic compounds and Functional groups that contain a basic Nitrogen Atom with a Lone pair. Pyridine is a Chemical compound with the formula C5[[Hydrogen H5]] N. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny This decreased basicity is attributed to the delocalization of the lone pair of electrons of the nitrogen atom in the aromatic ring. lone pair is a (valence electron pair without bonding or sharing with other Atoms They are found in the outermost Electron shell of an atom so lone pairs The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Pyrrole is a very weak base with a pKaH of about −4. Protonation results in loss of aromaticity, and is, therefore, unfavorable.
Synthesis
Many methods exist for the organic synthesis of pyrrole and its derivatives. Organic synthesis is a special branch of Chemical synthesis and is concerned with the construction of Organic compounds via Organic reactions Organic Classic named reactions are the Knorr pyrrole synthesis, the Hantzch pyrrole synthesis, and the Paal-Knorr synthesis. The Knorr pyrrole synthesis is a widely used Chemical reaction that synthesizes substituted Pyrroles (3. The Hantzch pyrrole synthesis is the Chemical reaction of β-ketoesters ( 1) with Ammonia (or primary Amines and α-halo Ketones ( The Paal-Knorr synthesis is a reaction where 14-diketones are converted to either Furans Thiophenes or Pyrroles The reaction is named after
The starting materials in the Piloty-Robinson pyrrole synthesis are 2 equivalents of an aldehyde and hydrazine[4][5]. An aldehyde is an organic compound containing a terminal Carbonyl group. Hydrazine is a Chemical compound with the formula N2H4 It has an Ammonia -like odor and is derived from the same industrial chemistry The product is a pyrrole with specific substituents in the 3 and 4 positions. The aldehyde reacts with the diamine to an intermediate di-imine (R–C=N−N=C–R), which, with added hydrochloric acid, gives ring-closure and loss of ammonia to the pyrrole. An imine is a Functional group or Chemical compound containing a Carbon – Nitrogen Double bond. Hydrochloric acid is the Solution of Hydrogen chloride ( H[[Chlorine Cl]] in water Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor
In one modification, propionaldehyde is reacted first with hydrazine and then with benzoyl chloride at high temperatures and assisted by microwave irradiation[6]:
In the second step, a [3,3]sigmatropic reaction takes place between two intermediates. Propionaldehyde or propanal is the Organic compound with the formula CH3CH2CHO Hydrazine is a Chemical compound with the formula N2H4 It has an Ammonia -like odor and is derived from the same industrial chemistry Benzoyl chloride, also known as benzenecarbonyl chloride is a colourless fuming liquid C6H5COCl with an irritating odour Microwave chemistry is the science of applying Microwave irradiation to chemical reactions. A Sigmatropic reaction in Organic chemistry is a Pericyclic reaction wherein the net result is one Sigma bond changed to another sigma bond.
Reactivity
Both NH and CH protons in pyrroles are moderately acidic and can be deprotonated with strong bases such as butyllithium and the metal hydrides. Deprotonation is a Chemistry term that refers to the removal of a Proton ( Hydrogen Cation H+ from a Molecule, forming In Chemistry, a base is most commonly thought of as an aqueous substance that can accept Protons This refers to the Brønsted-Lowry theory of acids and n -Butyllithium (abbreviated BuLi is the most prominent Organolithium reagent. Hydride is the name given to the negative Ion of Hydrogen, H− The resulting "pyrrolides" are nucleophilic. In Chemistry, a nucleophile (literally nucleus lover as in nucleus and phile) is a Reagent that forms a Chemical bond to Trapping of the conjugate base with an electrophile (e. Within the Brønsted - Lowry ( protonic) theory of acids and bases, a conjugate acid is the acid member HX of a pair of two compounds that transform In Chemistry, an electrophile (literally electron-lover) is a Reagent attracted to Electrons that participates in a chemical reaction by accepting g. , an alkyl or acyl halide) reveals which sites were deprotonated based on which ring positions actually react as nucleophiles. An acyl halide (also known as an acid halide) is a Chemical compound derived from an Oxoacid by replacing a Hydroxyl group with a The product distribution of such a reaction can often be complex and depends on the base used (especially the counterion, such as lithium from butyllithium or sodium from sodium hydride), existing substitution of the pyrrole, and the electrophile.
The resonance contributors of pyrrole provide insight to the reactivity of the compound. Like furan and thiophene, pyrrole is more reactive than benzene towards nucleophilic aromatic substitution because it is able to stabilize the positive charge of the intermediate carbanion. Furan, also known as furane and furfuran, is a heterocyclic Organic compound. Thiophene is the Heterocyclic compound with the formula C4H4S nucleophilic aromatic substitution is a Substitution reaction in Organic chemistry in which the Nucleophile displaces a good Leaving group, A carbanion is an Anion in which Carbon has an unshared pair of Electrons and bears a negative charge usually with three substituents for a total of eight This is because the nitrogen can donate a lone pair into the ring by resonance 
Pyrrole undergoes electrophilic aromatic substitution predominantly at the 2 and 5 positions, though the substitution product at positions 3 and 4 is obtained in low yields. Electrophilic aromatic substitution or EAS is an Organic reaction in which an atom usually Hydrogen, appended to an aromatic system is replaced Two such reactions that are especially significant for producing functionalized pyrroles are the Mannich reaction and the Vilsmeier-Haack reaction (depicted below) [7] [8], both of which are compatible with a variety of pyrrole substrates. The Mannich reaction is an Organic reaction which consists of an amino alkylation of an acidic proton placed next to a Carbonyl Functional group The Vilsmeier-Haack reaction (also called the Vilsmeier reaction) is the Chemical reaction of a substituted Amide ( 1) with Phosphorus oxychloride Reaction of pyrroles with formaldehyde form porphyrins. Formaldehyde is a Chemical compound with the formula H2CO It is the simplest Aldehyde —an organic compound containing a terminal Carbonyl A porphyrin is a heterocyclic Macrocycle derived from four Pyrroline subunits interconnected via their α carbon atoms via Methine bridges (=CH-
Pyrrole compounds can also participate in cycloaddition (Diels-Alder) reactions under certain conditions, such as Lewis acid catalysis, heating, or high pressure. A cycloaddition is a Pericyclic Chemical reaction, in which two π bonds are lost and two σ bonds are gained the resulting reaction is a The Diels-Alder reaction is an Organic chemical reaction (specifically a Cycloaddition) between a conjugated Diene and a substituted Alkene,
Commercial Uses
In a 1994 report released by five top cigarette companies, pyrrole is one of the 599 additives to cigarettes. Its use or purpose, however, is unknown, like that of most cigarette additives. A cigarette ( French "small Cigar " from cigar + -ette) is a product consumed through Smoking and manufactured [9]
See also
- Arsole, a moderately-aromatic arsenic analog
- Furan, an analog with an oxygen instead of the nitrogen
- Indole, a derivative with a fused benzene ring
- Phosphole, a non-aromatic phosphorus analog
- Polypyrrole
- Pyroluria
- Pyrroline, a partially saturated analog with one double bond
- Pyrrolidine, the saturated hydrogenated analog
- Simple aromatic rings
- Thiophene, an analog with a sulfur instead of the nitrogen atom. Arsole, rarely called arsenole, is a cyclic organoarsenic Chemical compound of the formula C4H5As Arsenic (ˈɑrsənɪk is a Chemical element that has the symbol As and Atomic number of 33 Furan, also known as furane and furfuran, is a heterocyclic Organic compound. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Indole is an Aromatic heterocyclic Organic compound. It has a bicyclic structure consisting of a six-membered Benzene ring fused to a five-membered Benzene, or benzol, is an organic Chemical compound and a known Carcinogen with the molecular formula C 6 H 6 Phosphole is the Organic compound with the Chemical formula C4H4PH it is the Phosphorus analog of Pyrrole. Phosphorus, (ˈfɒsfərəs is the Chemical element that has the symbol P and Atomic number 15 A Polypyrrole ( PPy) is a chemical compound formed from a number of connected Pyrrole ring structures Pyroluria (or malvaria from the term mauve factor) is a controversial diagnosis in the branch of Orthomolecular medicine, a branch of Alternative medicine Pyrrolines, also known under the name dihydropyrroles, are three different heterocyclic organic Chemical compounds which differ in the position Pyrrolidine, also known as tetrahydropyrrole, is an Organic compound with the molecular formula C4H9N Simple aromatic rings, also known as simple arenes or simple aromatics, are Aromatic Organic compounds that consist only of a conjugated Thiophene is the Heterocyclic compound with the formula C4H4S Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny
External links
- General Synthesis and Reactivity of Pyrrole
- Synthesis of pyrroles (overview of recent methods)
- Substitution reaction mechanisms of nitrogen-containing heteroaromatics
- Recent Review on Pyrrole Protection
References
- ^ # Loudon, Marc G. (2002). "Chemistry of Naphthalene and the Aromatic Heterocycles. ", Organic Chemistry, Fourth Edition, New York: Oxford University Press, 1135–1136. ISBN 0-19-511999-1.
- ^ Nelson, D. L. ; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.
- ^ The aromatic pathways of porphins, chlorins and bacteriochlorins Jonas Juse lius and Dage Sundholm Phys. Chem. Chem. Phys. , 2000, 2, 2145–2151 doi:10.1039/b000260g Open access
- ^ Piloty, O. Chem. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. Open access ( OA) is free immediate permanent full-text Online access for any user web-wide to digital scientific and scholarly material primarily Oskar Piloty ( 30 April 1866 &ndash 6 October 1915) was the German chemist. Ber. 1910, 43, 489.
- ^ Robinson, R.; Robinson, G. Sir Robert Robinson OM, PRS ( 13 September 1886 – 8 February 1975) was an English chemist and Nobel laureate M. J. Chem. Soc. 1918, 43, 639–644.
- ^ Microwave-Assisted Piloty-Robinson Synthesis of 3,4-Disubstituted Pyrroles Benjamin C. Milgram, Katrine Eskildsen, Steven M. Richter, W. Robert Scheidt, and Karl A. Scheidt J. Org. Chem.; 2007; 72(10) pp. The Journal of Organic Chemistry (abbreviated as J Org Chem or JOC) is a Scientific journal for original contributions of fundamental 3941–3944; (Note) doi:10.1021/jo070389+
- ^ Comparison of Benzene, Nitrobenzene, and Dinitrobenzene 2-Arylsulfenylpyrroles Jose R. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. Garabatos-Perera, Benjamin H. Rotstein, and Alison Thompson J. Org. Chem. 2007, 72, 7382–7385 doi:10.1021/jo070493r
- ^ The 2-sulfenyl group in the pyrrole substrate acts as an activating group and as a protective group that can be removed with Raney nickel
- ^ quitsmoking. The Journal of Organic Chemistry (abbreviated as J Org Chem or JOC) is a Scientific journal for original contributions of fundamental A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. A sulfenic acid is an Organosulfur compound and Oxoacid with the general formula R[[sulfur S]] O[[hydrogen H]] where R ≠ H In Organic chemistry, a Functional group is called an activating group if a Benzene Molecule to which it is attached more readily participates A protecting group or protective group is introduced into a molecule by chemical modification of a Functional group in order to obtain Chemoselectivity Raney nickel (ˈreɪniː ˈnɪkəl is a solid Catalyst composed of fine grains of a Nickel - Aluminium Alloy, used in many industrial processes about. com Link
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