不相応な、不釣合な

関: disproportionately、unsuited

WordNet

not proportionate
out of proportion (同)disproportional
to a disproportionate degree; "his benefits were disproportionately generous"
out of proportion; "this wall is disproportionately long"

PrepTutorEJDIC

不均衡の;(…に)不釣り合いな《+『to』+『名』》
不適当な,適合しない;(…に)不適当な《+to(for)+名》

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2017/07/21 23:38:00」(JST)

wiki en

[Wiki en表示]

Disproportionation is a specific type of redox reaction in which an element from a reaction undergoes both oxidation and reduction to form two different products.

Overview

For example, the UV photolysis of mercury(I) chloride Hg₂Cl₂ → Hg + HgCl₂ is a disproportionation. Mercury(I) is a diatomic dication Hg2+
2. In this reaction, the chemical bond in the molecular ion is broken, and one mercury atom is reduced to mercury(0), and the other is oxidized to mercury(II).

A similar type of reaction, but in which no element changes oxidation number, is the acid-base disproportionation reaction observed when an amphiprotic species reacts with itself. Two common examples for conjugated bases of polyprotic acids such as bicarbonate and dihydrogenophosphate are respectively:

2 HCO−
3 → CO2−
3 + H₂CO₃

2 H
2PO−
4 → HPO2−
4 + H₃PO₄

The oxidation numbers remain constant in these acid-base reactions: O = −2, H = +1, C = +4, P = +5. This is also called autoionization.

Another variant on disproportionation is radical disproportionation, in which two radicals form an alkane and alkene.

Reverse reaction

The reverse of disproportionation, when a compound in an intermediate oxidation state is formed from compounds in lower and higher oxidation states, is called comproportionation, also known as symproportionation.

History

The first disproportionation reaction to be studied in detail was:

2 Sn²⁺ → Sn⁴⁺ + Sn

This was examined using tartrates by Johan Gadolin in 1788. In the Swedish version of his paper he called it 'söndring'.^[1]^[2]

Examples

Chlorine gas reacts with dilute sodium hydroxide to form sodium chloride, sodium chlorate and water. The ionic equation for this reaction is as follows:^[3]

3 Cl₂ + 6 OH⁻ → 5 Cl⁻ + ClO₃⁻ + 3 H₂O

The chlorine gas reactant is in oxidation state 0. In the products, the chlorine in the Cl⁻ ion has an oxidation number of −1, having been reduced, whereas the oxidation number of the chlorine in the ClO₃⁻ ion is +5, indicating that it has been oxidized.

Bromine fluoride undergoes disproportionation reaction for form bromine trifluoride:^[4]

3 BrF → BrF₃ + Br₂

The dismutation of superoxide free radical to hydrogen peroxide and oxygen, catalysed in living systems by the enzyme superoxide dismutase:

2 O₂⁻ + 2 H⁺ → H₂O₂ + O₂

The oxidation state of oxygen is −1/2 in the superoxide free radical anion, −1 in hydrogen peroxide and 0 in dioxygen.

In the Cannizzaro reaction, an aldehyde is converted into an alcohol and a carboxylic acid. In the related Tishchenko reaction, the organic redox reaction product is the corresponding ester. In the Kornblum–DeLaMare rearrangement, a peroxide is converted to a ketone and an alcohol.
The disproportionation of hydrogen peroxide into water and oxygen catalysed by either potassium iodide or the enzyme catalase:

2 H₂O₂ → 2 H₂O + O₂

The Boudouard reaction is for example used in the HiPco method for producing carbon nanotubes, high-pressure carbon monoxide disproportionates when catalysed on the surface of an iron particle:

2 CO → C + CO₂

Nitrogen has oxidation state +IV in nitrogen dioxide, but when this compound reacts with water, it forms both nitric acid and nitrous acid, where nitrogen has oxidation states +V and +III respectively:

2 NO₂ + H₂O → HNO₃ + HNO₂

Biochemistry

In 1937, Hans Adolf Krebs, who discovered the citric acid cycle bearing his name, confirmed the anaerobic dismutation of pyruvic acid in lactic acid, acetic acid and CO₂ by certain bacteria according to the global reaction:^[5]

2 pyruvic acid + H₂O → lactic acid + acetic acid + CO₂

The dismutation of pyruvic acid in other small organic molecules (ethanol + CO₂, or lactate and acetate, depending on the environmental conditions) is also an important step in fermentation reactions. Fermentation reactions can also be considered as disproportionation or dismutation biochemical reactions. Indeed, the donor and acceptor of electrons in the redox reactions supplying the chemical energy in these complex biochemical systems are the same organic molecules simultaneously acting as reductant or oxidant.

Another example of biochemical dismutation reaction is the disproportionation of acetaldehyde into ethanol and acetic acid.^[6]

While in respiration electrons are transferred from substrate (electron donor) to an electron acceptor, in fermentation part of the substrate molecule itself accepts the electrons. Fermentation is therefore a type of disproportionation, and does not involve an overall change in oxidation state of the substrate. Most of the fermentative substrates are organic molecules. However, a rare type of fermentation may also involve the disproportionation of inorganic sulfur compounds in certain sulfate-reducing bacteria.^[7]

References

^ Gadolin Johan (1788) K. Sv. Vet. Acad. Handl. 1788, 186-197.
^ Gadolin Johan (1790) Crells Chem. Annalen 1790, I, 260-273.
^ Charlie Harding, David Arthur Johnson, Rob Janes, (2002), Elements of the P Block, Published by Royal Society of Chemistry, ISBN 0-85404-690-9
^ Non Aqueous Media.
^ Krebs, H.A. (1937). "LXXXVIII - Dismutation of pyruvic acid in gonoccus and staphylococcus" (PDF). Biochem J. 31 (4): 661–671. PMC 1266985 . PMID 16746383.
^ Biochemical basis of mitochondrial acetaldehyde dismutation in Saccharomyces cerevisiae
^ A novel type of energy metabolism involving fermentation of inorganic sulfur compounds.

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 多系統萎縮症：臨床的特徴および診断 multiple system atrophy clinical features and diagnosis
2. 胆汁うっ滞系酵素の測定（アルカリホスファターゼ、5' -ヌクレオチダーゼ、γ-グルタミルトランスペプチダーゼなど） enzymatic measures of cholestasis eg alkaline phosphatase 5 nucleotidase gamma glutamyl transpeptidase
3. 糖尿病の母親の小児 infant of a diabetic mother
4. 妊娠中の気道変化 respiratory tract changes during pregnancy
5. 薬物性肝障害 drug induced liver injury

English Journal

Understanding controls on redox processes in floodplain sediments of the Upper Colorado River Basin.

Noël V1, Boye K2, Kukkadapu RK3, Bone S1, Lezama Pacheco JS2, Cardarelli E4, Janot N1, Fendorf S4, Williams KH5, Bargar JR6.
The Science of the total environment.Sci Total Environ.2017 Dec 15;603-604:663-675. doi: 10.1016/j.scitotenv.2017.01.109. Epub 2017 Mar 27.
PMID 28359569

Sexual Networking and Partner Characteristics Among Single, African, Caribbean, and Black Youth in Windsor, Ontario.

Kerr J1,2, Maticka-Tyndale E3, Bynum S4, Mihan R3; ACBY Team.
Archives of sexual behavior.Arch Sex Behav.2017 Oct;46(7):1891-1899. doi: 10.1007/s10508-016-0749-8. Epub 2016 Apr 29.
PMID 27129534

Hearing health access in developing countries.

Harris MS1, Dodson EE.
Current opinion in otolaryngology & head and neck surgery.Curr Opin Otolaryngol Head Neck Surg.2017 Oct;25(5):353-358. doi: 10.1097/MOO.0000000000000392.
PMID 28678066

Inhibition of NFE2L2-Antioxidant Response Element Pathway by Mitochondrial Reactive Oxygen Species Contributes to Development of Cardiomyopathy and Left Ventricular Dysfunction in Chagas Disease.

Wen JJ1, Porter C2,3, Garg NJ1,4,5.
Antioxidants & redox signaling.Antioxid Redox Signal.2017 Sep 20;27(9):550-566. doi: 10.1089/ars.2016.6831. Epub 2017 Jul 13.
PMID 28132522

Japanese Journal

中世禅林詩学における言語(の〈外部〉[彼岸])への視座 : 言語と〈心〉の不均衡な呼応関係 <論文>

山藤夏郎,サントウナツオ,Santoh Natsuo
日本研究 (26), 1-18, 2013-03-31
NAID 120005245590

Study on Current Status and Task of Sawmills Located in the Woodland of Korea

Choi Soo Im,Kang Hag Mo,Lee Chong Kyu,Sato Noriko,佐藤宣子
Journal of the Faculty of Agriculture, Kyushu University 58(1), 183-190, 2013-02-00
… there are many problems such as the intensifying competition in securing raw materials due to the disadvantage in the sustainable use of resources according to the disproportionate distribution of age groups, the low–grade timber with low utilization values, short supply of timber inside Korea, the increase of imported timber price, the pettiness of the timer industry and lack of effort to develop technology, the supremacy of lumberjack over the raw timber price and circulation, limitation in making precise estimation and prediction about the …
NAID 120005227266

REMARKABLE INCREASE OF CYTOCHROME C OXIDASE SUBUNIT I AFTER GLOBAL CEREBRAL ISCHEMIA

Takahashi Yusuke,Sugawara Taku,Miyazaki Toshio,Hideaki Itoh,Mizoi Kazuo
秋田医学 39(2), 53-59, 2013-02-00
… In this study, a massive increase in COX I, which is disproportionate to COX IV was observed at 1 and 6 h after lethal ischemia, preceding delayed neuronal death. …
NAID 110009575391

Anodic Dissolution of Copper in Oxygenated Sulfuric Acid Solution as Examined by Rotating Ring-Disk Electrode

KANZAKI Yasushi,BRUCKENSTEIN Stanley
Electrochemistry 81(7), 547-552, 2013
… A characteristic property of the anodic process is that the oxidation process Cu → Cu2+ involves the detectable intermediate Cu+, which should disproportionate into Cu and Cu2+ in the thermodynamic equilibrium state. …
NAID 130003376730