Pyridine-N-oxide

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Pyridine-N-oxide
Pyridine-N-oxide.png
Pyridine-N-oxide-3D-balls.png
Names
Preferred IUPAC name
5-Pyridin-1-one
Other names
Pyridine-1-oxide
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.010.705 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
  • InChI=1S/C5H5NO/c7-6-4-2-1-3-5-6/h1-5H Yes check.svgY
    Key: ILVXOBCQQYKLDS-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C5H5NO/c7-6-4-2-1-3-5-6/h1-5H
    Key: ILVXOBCQQYKLDS-UHFFFAOYAZ
  • c1cc[n+](cc1)[O-]
Properties
C5H5NO
Molar mass 95.101 g·mol−1
AppearanceColourless solid
Melting point 65 to 66 °C (149 to 151 °F; 338 to 339 K)
Boiling point 270 °C (518 °F; 543 K)
high
Acidity (pKa)0.8 (of conjugate acid)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

Pyridine-N-oxide is the heterocyclic compound with the formula C5H5NO. This colourless, hygroscopic solid is the product of the oxidation of pyridine. It was originally prepared using peroxyacids as the oxidising agent. The compound is used infrequently as an oxidizing reagent in organic synthesis. [1]

Contents

Structure

The structure of pyridine-N-oxide is very similar to that of pyridine with respect to the parameters for the ring. The molecule is planar. The N-O distance is 1.34 Å. The C-N-C angle is 124°, 7° wider than in pyridine. [2]

Synthesis

The oxidation of pyridine can be achieved with a number of peracids including peracetic acid and perbenzoic acid. [3] Oxidation can also be effected by a modified Dakin reaction using a urea-hydrogen peroxide complex, [4] and sodium perborate [5] or, using methylrhenium trioxide (CH
3
ReO
3
) as catalyst, with sodium percarbonate. [6]

Reactions

Pyridine N-oxide is five orders of magnitude less basic than pyridine: the pKa of protonated pyridine-N-oxide is 0.8. [7] Protonated derivatives are isolable, e.g., [C5H5NOH]Cl. [3] Further demonstrating its (feeble) basicity, pyridine-N-oxide also serves as a ligand in coordination chemistry. A host of transition metal complexes of pyridine-N-oxides are known.

Treatment of the pyridine-N-oxide with phosphorus oxychloride gives 4- and 2-chloropyridines. [8]

The N-oxides of various pyridines are precursors to useful drugs: [9]

Safety

The compound is a skin irritant. [1]

Further reading

Related Research Articles

Pyrimidine is an aromatic, heterocyclic, organic compound similar to pyridine. One of the three diazines, it has nitrogen atoms at positions 1 and 3 in the ring. The other diazines are pyrazine and pyridazine.

<span class="mw-page-title-main">Pyridine</span> Heterocyclic aromatic organic compound

Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one methine group (=CH−) replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a distinctive, unpleasant fish-like smell. Pyridine is colorless, but older or impure samples can appear yellow, due to the formation of extended, unsaturated polymeric chains, which show significant electrical conductivity. The pyridine ring occurs in many important compounds, including agrochemicals, pharmaceuticals, and vitamins. Historically, pyridine was produced from coal tar. As of 2016, it is synthesized on the scale of about 20,000 tons per year worldwide.

<span class="mw-page-title-main">Quinoline</span> Chemical compound

Quinoline is a heterocyclic aromatic organic compound with the chemical formula C9H7N. It is a colorless hygroscopic liquid with a strong odor. Aged samples, especially if exposed to light, become yellow and later brown. Quinoline is only slightly soluble in cold water but dissolves readily in hot water and most organic solvents. Quinoline itself has few applications, but many of its derivatives are useful in diverse applications. A prominent example is quinine, an alkaloid found in plants. Over 200 biologically active quinoline and quinazoline alkaloids are identified. 4-Hydroxy-2-alkylquinolines (HAQs) are involved in antibiotic resistance.

<span class="mw-page-title-main">Sodium percarbonate</span> Chemical compound

Sodium percarbonate, or sodium carbonate peroxide is a chemical substance with formula Na
2
H
3
CO
6
. It is an adduct of sodium carbonate and hydrogen peroxide whose formula is more properly written as 2 Na
2
CO
3
 · 3 H
2
O
2
. It is a colorless, crystalline, hygroscopic and water-soluble solid. It is sometimes abbreviated as SPC. It contains 32.5% by weight of hydrogen peroxide.

<span class="mw-page-title-main">Hydrogen peroxide - urea</span> Chemical compound

Hydrogen peroxide - urea is a white crystalline solid chemical compound composed of equal amounts of hydrogen peroxide and urea. It contains solid and water-free hydrogen peroxide, which offers a higher stability and better controllability than liquid hydrogen peroxide when used as an oxidizing agent. Often called carbamide peroxide in dentistry, it is used as a source of hydrogen peroxide when dissolved in water for bleaching, disinfection and oxidation.

<span class="mw-page-title-main">Peroxy acid</span> Organic acid having a peroxide bond

A peroxy acid is an acid which contains an acidic –OOH group. The two main classes are those derived from conventional mineral acids, especially sulfuric acid, and the peroxy derivatives of organic carboxylic acids. They are generally strong oxidizers.

<span class="mw-page-title-main">Hexamethylphosphoramide</span> Chemical compound

Hexamethylphosphoramide, often abbreviated HMPA, is a phosphoramide (an amide of phosphoric acid) with the formula [(CH3)2N]3PO. This colorless liquid is a useful reagent in organic synthesis.

<span class="mw-page-title-main">Carbonyldiimidazole</span> Chemical compound

1,1'-Carbonyldiimidazole (CDI) is an organic compound with the molecular formula (C3H3N2)2CO. It is a white crystalline solid. It is often used for the coupling of amino acids for peptide synthesis and as a reagent in organic synthesis.

Sodium perborate is chemical compound whose chemical formula may be written NaH2BO4, Na2H4B2O8, or, more properly, [Na+]2[B2O4(OH)4]2−. Its name is sometimes abbreviated as PBS.

Dioxolane is a heterocyclic acetal with the chemical formula (CH2)2O2CH2. It is related to tetrahydrofuran (THF) by replacement of the methylene group (CH2) at the 2-position with an oxygen atom. The corresponding saturated 6-membered C4O2 rings are called dioxanes. The isomeric 1,2-dioxolane (wherein the two oxygen centers are adjacent) is a peroxide. 1,3-dioxolane is used as a solvent and as a comonomer in polyacetals.

<span class="mw-page-title-main">2-Pyridone</span> Chemical compound

2-Pyridone is an organic compound with the formula C
5
H
4
NH(O)
. It is a colourless solid. It is well known to form hydrogen bonded dimers and it is also a classic case of a compound that exists as tautomers.

<span class="mw-page-title-main">Dakin oxidation</span> Organic redox reaction that converts hydroxyphenyl aldehydes or ketones into benzenediols

The Dakin oxidation (or Dakin reaction) is an organic redox reaction in which an ortho- or para-hydroxylated phenyl aldehyde (2-hydroxybenzaldehyde or 4-hydroxybenzaldehyde) or ketone reacts with hydrogen peroxide (H2O2) in base to form a benzenediol and a carboxylate. Overall, the carbonyl group is oxidised, whereas the H2O2 is reduced.

<span class="mw-page-title-main">Methylrhenium trioxide</span> Chemical compound

Methylrhenium trioxide, also known as methyltrioxorhenium(VII), is an organometallic compound with the formula CH3−ReO3. It is a volatile, colourless solid that has been used as a catalyst in some laboratory experiments. In this compound, rhenium has a tetrahedral coordination geometry with one methyl and three oxo ligands. The oxidation state of rhenium is +7.

The Petrenko-Kritschenko reaction is a classic multicomponent-name reaction that is closely related to the Robinson–Schöpf tropinone synthesis, but was published 12 years earlier.

<span class="mw-page-title-main">2-Mercaptopyridine</span> Chemical compound

2-Mercaptopyridine is an organosulfur compound with the formula HSC5H4N. This yellow crystalline solid is a derivative of pyridine. The compound and its derivatives serve primarily as acylating agents. A few of 2-mercaptopyridine’s other uses include serving as a protecting group for amines and imides as well as forming a selective reducing agent. 2-Mercaptopyridine oxidizes to 2,2’-dipyridyl disulfide.

The Minisci reaction is a named reaction in organic chemistry. It is a nucleophilic radical substitution to an electron deficient aromatic compound, most commonly the introduction of an alkyl group to a nitrogen containing heterocycle. The reaction was published in 1971 by F. Minisci. In the case of N-Heterocycles, the conditions must be acidic to ensure protonation of said heterocycle. A typical reaction is that between pyridine and pivalic acid with silver nitrate, sulfuric acid and ammonium persulfate to form 2-tert-butylpyridine. The reaction resembles Friedel-Crafts alkylation but with opposite reactivity and selectivity.

<span class="mw-page-title-main">Trifluoroperacetic acid</span> Chemical compound

Trifluoroperacetic acid is an organofluorine compound, the peroxy acid analog of trifluoroacetic acid, with the condensed structural formula CF
3
COOOH
. It is a strong oxidizing agent for organic oxidation reactions, such as in Baeyer–Villiger oxidations of ketones. It is the most reactive of the organic peroxy acids, allowing it to successfully oxidise relatively unreactive alkenes to epoxides where other peroxy acids are ineffective. It can also oxidise the chalcogens in some functional groups, such as by transforming selenoethers to selones. It is a potentially explosive material and is not commercially available, but it can be quickly prepared as needed. Its use as a laboratory reagent was pioneered and developed by William D. Emmons.

<span class="mw-page-title-main">MoOPH</span> Chemical compound

MoOPH, also known as oxodiperoxymolybdenum(pyridine)-(hexamethylphosphoric triamide), is a reagent used in organic synthesis. It contains a molybdenum(VI) center with multiple oxygen ligands, coordinated with pyridine and HMPA ligands. It is an electrophilic source of oxygen that reacts with enolates and related structures, and thus can be used for alpha-hydroxylation of carbonyl-containing compounds. Other reagents used for alpha-hydroxylation via enol or enolate structures include Davis oxaziridine, oxygen, and various peroxyacids. This reagent was first utilized by Edwin Vedejs as an efficient alpha-hydroxylating agent in 1974 and an effective preparative procedure was later published in 1978.

<span class="mw-page-title-main">Metal peroxide</span>

Metal peroxides are metal-containing compounds with ionically- or covalently-bonded peroxide (O2−
2
) groups. This large family of compounds can be divided into ionic and covalent peroxide. The first class mostly contains the peroxides of the alkali and alkaline earth metals whereas the covalent peroxides are represented by such compounds as hydrogen peroxide and peroxymonosulfuric acid (H2SO5). In contrast to the purely ionic character of alkali metal peroxides, peroxides of transition metals have a more covalent character.

The Hantzsch pyridine synthesis or Hantzsch dihydropyridine synthesis is a multi-component organic reaction between an aldehyde such as formaldehyde, 2 equivalents of a β-keto ester such as ethyl acetoacetate and a nitrogen donor such as ammonium acetate or ammonia. The initial reaction product is a dihydropyridine which can be oxidized in a subsequent step to a pyridine. The driving force for this second reaction step is aromatization. This reaction was reported in 1881 by Arthur Rudolf Hantzsch.

References

  1. 1 2 Kilényi, S. Nicholas; Mousseau, James J. (20 September 2015). "PyridineN-Oxide". Pyridine N-Oxide. Encyclopedia of Reagents for Organic Synthesis . John Wiley & Sons. pp. 1–6. doi:10.1002/047084289X.rp283.pub2. ISBN   9780470842898.
  2. Ülkü, D.; Huddle, B. P.; Morrow, J. C. (1971). "The Crystal Structure of Pyridine 1-oxide". Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry. 27 (2): 432–436. doi:10.1107/S0567740871002334.
  3. 1 2 Mosher, H. S.; Turner, L.; Carlsmith, A. (1953). "Pyridine-N-oxide". Org. Synth. 33: 79. doi:10.15227/orgsyn.033.0079.
  4. Varma, Rajender S.; Naicker, Kannan P. (1999). "The Urea−Hydrogen Peroxide Complex: Solid-State Oxidative Protocols for Hydroxylated Aldehydes and Ketones (Dakin Reaction), Nitriles, Sulfides, and Nitrogen Heterocycles". Org. Lett. 1 (2): 189–192. doi:10.1021/ol990522n.
  5. McKillop, Alexander; Kemp, Duncan (1989). "Further functional group oxidations using sodium perborate". Tetrahedron . 45 (11): 3299–3306. doi:10.1016/S0040-4020(01)81008-5.
  6. Jain, Suman L.; Joseph, Jomy K.; Sain, Bir (2006). "Rhenium-Catalyzed Highly Efficient Oxidations of Tertiary Nitrogen Compounds to N-Oxides Using Sodium Percarbonate as Oxygen Source". Synlett . 2006 (16): 2661–2663. doi:10.1055/s-2006-951487.
  7. Chmurzyński, L. (1996). "Studies on correlations of acid-base properties of substituted pyridine N-oxides in solutions. Part 1. Correlations of the p Ka values in non-aqueous solvents and water". Analytica Chimica Acta. 321 (2–3): 237–244. doi:10.1016/0003-2670(95)00594-3.
  8. Scriven, E. F. V. (1984). "Pyridines and their Benzo Derivatives: (ii) Reactivity at Ring Atoms". In Katritzky, Alan R.; Rees, Charles Wayne; Meth-Cohn, Otto (eds.). Comprehensive Heterocyclic Chemistry: The Structure, Reactions, Synthesis and Uses of Heterocyclic Compounds. Vol. 2. Pergamon Press. pp. 165–314. doi:10.1016/B978-008096519-2.00027-8. ISBN   9780080307015.
  9. Shimizu, Shinkichi; Watanabe, Nanao; Kataoka, Toshiaki; Shoji, Takayuki; Abe, Nobuyuki; Morishita, Sinji; Ichimura, Hisao (2000). Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a22_399.