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関: both sexes

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having characteristics of both an acid and a base and capable of reacting as either (同)amphiprotic
an antibiotic and antifungal agent

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/05/05 22:19:18」(JST)

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In chemistry, an amphoteric compound is a molecule or ion that can react both as an acid as well as a base.^[1] The word is derived from the Greek word amphoteroi (ἀμφότεροι) meaning "both". Many metals (such as copper, zinc, tin, lead, aluminium, and beryllium) form amphoteric oxides or hydroxides. Amphoterism depends on the oxidation states of the oxide.

One type of amphoteric species are amphiprotic molecules, which can either donate or accept a proton (H⁺). Examples include amino acids and proteins, which have amine and carboxylic acid groups, and self-ionizable compounds such as water.

Ampholytes are amphoteric molecules that contain both acidic and basic groups and will exist mostly as zwitterions in a certain range of pH. The pH at which the average charge is zero is known as the molecule's isoelectric point. Ampholytes are used to establish a stable pH gradient for use in isoelectric focusing.

Amphoteric oxides and hydroxides^[2]

Zinc oxide (ZnO) reacts with both acids and with bases:

In acid: ZnO + 2H⁺ → Zn²⁺ + H₂O
In base: ZnO + H₂O + 2 OH⁻ → [Zn(OH)₄]²⁻

This reactivity can be used to separate different cations, such as zinc(II), which dissolves in base, from manganese(II), which does not dissolve in base.

Aluminium hydroxide is also amphoteric:

As a base (neutralizing an acid): Al(OH)₃ + 3 HCl → AlCl₃ + 3 H₂O
As an acid (neutralizing a base): Al(OH)₃ + NaOH → Na[Al(OH)₄]

Some other amphoteric compounds include:

Beryllium hydroxide
- with acid: Be(OH)₂ + 2 HCl → BeCl₂ + 2 H₂O
- with base: Be(OH)₂ + 2 NaOH → Na₂[Be(OH)₄]
Aluminium oxide
- with acid: Al₂O₃ + 3 H₂O + 6 H₃O⁺(aq) → 2 [Al(H₂O)₆]³⁺(aq)
- with base: Al₂O₃ + 3 H₂O + 2 OH⁻(aq) → 2 [Al(OH)₄]⁻(aq)
Lead(II) oxide
- with acid: PbO + 2 HCl → PbCl₂ + H₂O
- with base: PbO + 2 NaOH + H₂O → Na₂[Pb(OH)₄]

Some other elements which form amphoteric oxides are gallium, indium, scandium, titanium, zirconium, vanadium, chromium, iron, cobalt, copper, silver, gold, germanium, tin, antimony, bismuth, and tellurium.^[3]

Amphiprotic molecules

According to the Brønsted-Lowry theory of acids and bases: acids are proton donors and bases are proton acceptors.^[4] An amphiprotic molecule (or ion) can either donate or accept a proton, thus acting either as an acid or a base. Water, amino acids, hydrogen carbonate ions and hydrogen sulfate ions are common examples of amphiprotic species. Since they can donate a proton, all amphiprotic substances contain a hydrogen atom. Also, since they can act like an acid or a base, they are amphoteric.

Examples

A common example of an amphiprotic substance is the hydrogen carbonate ion, which can act as a base:

HCO₃⁻ + H₃O⁺ → H₂CO₃ + H₂O

or as an acid:

HCO₃⁻ + OH⁻ → CO₃²⁻ + H₂O

Thus, it can effectively accept or donate a proton.

Water is the most common example, acting as a base when reacting with an acid such as hydrogen chloride:

H₂O + HCl → H₃O⁺ + Cl⁻,

and acting as an acid when reacting with a base such as ammonia:

H₂O + NH₃ → NH₄⁺ + OH⁻

Not all amphoteric substances are amphiprotic

Although an amphiprotic species must be amphoteric, the converse is not true. For example, the metal oxide ZnO contains no hydrogen and cannot donate a proton. Instead it is a Lewis acid whose Zn atom accepts an electron pair from the base OH⁻. The other metal oxides and hydroxides mentioned above also function as Lewis acids rather than Brønsted acids.

References

^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "amphoteric".
^ Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. pp. 173–4. ISBN 978-0130399137.
^ CHEMIX School & Lab - Software for Chemistry Learning, by Arne Standnes (program download required)
^ R.H. Petrucci, W.S. Harwood, and F.G. Herring, "General Chemistry" (8th edn, Prentice-Hall 2002), p.669

English Journal

Carboxymethyl chitosan-modified magnetic-cored dendrimer as an amphoteric adsorbent.

Kim HR1, Jang JW2, Park JW3.
Journal of hazardous materials.J Hazard Mater.2016 Nov 5;317:608-16. doi: 10.1016/j.jhazmat.2016.06.025. Epub 2016 Jun 14.
Carboxymethyl chitosan-modified magnetic-cored dendrimers (CCMDs) were successfully synthesized in a three step method. The synthesized samples were characterized using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, vibrating sample magnetometer, thermogravimetry
PMID 27351905

Agarose functionalization: Synthesis of PEG-agarose amino acid nano-conjugate - its structural ramifications and interactions with BSA in a varying pH regime.

Chudasama NA1, Prasad K2, Siddhanta AK3.
Carbohydrate polymers.Carbohydr Polym.2016 Oct 20;151:735-42. doi: 10.1016/j.carbpol.2016.06.020. Epub 2016 Jun 6.
In a rapid one-step method protein-mimicking large agarose amino acid framework (AAE; GPC 156.7kDa) was conjugated with polyethylene glycol (PEG 9kDa) affording nano-sized PEGylated amphoteric agarose (PEG-AAE; <10nm; DLS) containing amino, carboxyl and ester groups [overall degree of substitutio
PMID 27474620

Effect of resin charged functional group, porosity, and chemical matrix on the long-term pharmaceutical removal mechanism by conventional ion exchange resins.

Wang W1, Li X1, Yuan S1, Sun J1, Zheng S2.
Chemosphere.Chemosphere.2016 Oct;160:71-9. doi: 10.1016/j.chemosphere.2016.06.073. Epub 2016 Jun 28.
This study attempted to clarify the long-term pharmaceutical removal mechanism from sewage treatment plant effluent during the cyclical adsorption-regeneration operation of 5 commercial resin-based fixed-bed reactors with the simultaneous occurrence of electrostatic interactions and complex non-elec
PMID 27367175

Japanese Journal

Characterization of Selenium Species in Extract from Niboshi (a Processed Japanese Anchovy)

Yoshida Sakura,Haratake Mamoru,Fuchigami Takeshi [他]
Chemical and Pharmaceutical Bulletin 60(3), 348-353, 2012-03
… Ion-exchange chromatographicseparations revealed that most of the selenium species in the extract possess anionic and/or amphoteric characteristics.One of these selenium species from the Niboshi extract was detected at m/z 577 for 80Se by massspectrometry subsequent to ion-pair extraction. …
NAID 40019161382

L-リジン骨格を含むポリ(メタ)アクリルアミドの調製と線溶活性への影響 (特集号メディカルポリマー)

白石浩平,脇坂真伍,里崎順二 [他]
高分子論文集 69(1), 39-46, 2012
NAID 40019187398

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★リンクテーブル★

リンク元	「両性」「both sexes」
拡張検索	「amphotericin」「lipsomal amphotericin B」

「両性」

　　[★]

英: both sexes、amphoteric

「both sexes」

　　[★]

両性

関: amphoteric

「amphotericin」

　　[★]

アンホテリシン、アムホテリシン

関: amphotericin B

「lipsomal amphotericin B」

　　[★] アムホテリシンBリポソーム製剤

[1] IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "amphoteric".

[2] Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. pp. 173–4. ISBN 978-0130399137.

[3] CHEMIX School & Lab - Software for Chemistry Learning, by Arne Standnes (program download required)

[4] R.H. Petrucci, W.S. Harwood, and F.G. Herring, "General Chemistry" (8th edn, Prentice-Hall 2002), p.669

匿名

検索

案内

案内

amphoteric

WordNet

Wikipedia preview

wiki en

Contents

Amphoteric oxides and hydroxides^[2]

Amphiprotic molecules

Examples

Not all amphoteric substances are amphiprotic

See also

References

English Journal

Japanese Journal

Related Links

Related Pictures

★リンクテーブル★

「両性」

「both sexes」

「amphotericin」

「lipsomal amphotericin B」

Acids and bases
pH Reaction Titration Extraction Dissociation constant (acid) Acid strength Acidity function Buffer solutions Proton affinity Self-ionization of water Amphoterism
Acid types
Brønsted Lewis Mineral Organic Strong Superacids Weak
Base types
Brønsted Lewis Organic Strong Superbases Non-nucleophilic Weak
v t e

匿名

検索

案内

amphoteric

WordNet

Wikipedia preview

wiki en

Contents

Amphoteric oxides and hydroxides[2]

Amphiprotic molecules

Examples

Not all amphoteric substances are amphiprotic

See also

References

English Journal

Japanese Journal

Related Links

Related Pictures

★リンクテーブル★

「両性」

「both sexes」

「amphotericin」

「lipsomal amphotericin B」

Amphoteric oxides and hydroxides^[2]