Quaternary ammonium cation

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Quaternary ammonium compound
)
aryl
groups. Also, the R groups may be connected.

In

oilfield parlance) are salts of quaternary ammonium cations. Polyquats are a variety of engineered polymer
forms which provide multiple quat molecules within a larger molecule.

Quats are used in consumer applications including as

antimicrobials (such as detergents and disinfectants), fabric softeners, and hair conditioners. As an antimicrobial, they are able to inactivate enveloped viruses (such as SARS-CoV-2). Quats tend to be gentler on surfaces than bleach-based disinfectants, and are generally fabric-safe.[2]

"Top" view of Bu4N+ as determined by X-ray crystallography.[3]
"Side" view of Bu4N+ as determined by X-ray crystallography.[3]

Synthesis

Quaternary ammonium compounds are prepared by the

methyl chloride.[4]

The quaternization of alkyl amines by alkyl halides is widely documented.[5] In older literature this is often called a Menshutkin reaction, however modern chemists usually refer to it simply as quaternization.[6] The reaction can be used to produce a compound with unequal alkyl chain lengths; for example when making cationic surfactants one of the alkyl groups on the amine is typically longer than the others.[7] A typical synthesis is for benzalkonium chloride from a long-chain alkyldimethylamine and benzyl chloride:

Reactions

Quaternary ammonium cations are unreactive toward even strong

oxidants, and acids. They also are stable toward most nucleophiles. The latter is indicated by the stability of the hydroxide salts such as tetramethylammonium hydroxide and tetrabutylammonium hydroxide even at elevated temperatures. The halflife of Me4NOH in 6M NaOH at 160 °C is >61 h.[8]

Because of their resilience, many unusual anions have been isolated as the quaternary ammonium salts. Examples include

Bu+
4 salt.[9][10]

With exceptionally strong bases, quat cations degrade. They undergo Sommelet–Hauser rearrangement[11] and Stevens rearrangement,[12] as well as dealkylation under harsh conditions or in presence of strong nucleophiles, like thiolates. Quaternary ammonium cations containing N−C−C−H units can also undergo the Hofmann elimination and Emde degradation.

phase transfer agent.[13] ADBACs are a mixture
of alkylbenzyldimethylammonium chlorides, in which the alkyl group has various even-numbered alkyl chain lengths.

Examples

Applications

Quaternary ammonium salts are used as

electrolytic capacitors and spermicidal jellies also contain quaternary ammonium salts. Quats are also used in contraception formulations, veterinary products, diagnostic testing, vaccine production, and nasal formulations. [14]

Concerns have been raised about the level of understanding of safety profile of quat disinfectants on people. As of August 2020, half of disinfectants the United States Environmental Protection Agency suggested as effective against COVID-19 contained one of the quats, and often a quat as the sole ingredient.[15] Salmonella and E. coli O157:H7 exposed to quats have developed cross resistance to antibiotics. A subject of concern is the potential effect of increased use of quats related to COVID-19 pandemic on antibiotic resistance in a larger microbial community in nature and engineered environment.[16]

Medicines

Buscopan is one of many spasmo­lytics (anti-spasm drugs) that feature the quaternary ammonium functional group.[17]

Quaternary ammonium compounds have antimicrobial activity.

viruses (such as SARS-CoV-2),[19][20] most quaternary ammonium compounds are believed to act by disrupting the cell membrane or viral envelope.[21] (Some QACs, such as dequalinium and similar bis-QACs, show evidence of a different mode of action.)[22]

Quaternary ammonium compounds are lethal to a wide variety of organisms except

mycobacteria, and bacteria in biofilms due to them having additional layers that need to be penetrated or disrupted. Some bacteria such as MRSA have acquired resistance genes, qacA/B and qacC/D, that pump the cation out of the cell.[22]

Phase transfer catalysts

In organic chemistry, quaternary ammonium salts are employed as

phase transfer catalysts (PTCs). Such catalysts accelerate reactions between reagents dissolved in immiscible solvents. The highly reactive reagent dichlorocarbene is generated via PTC by reaction of chloroform and aqueous sodium hydroxide.[citation needed
]

Anion exchange resins, in the form of beads, contain quaternary ammonium ions bound to a polymer.[25]

Fabric softeners and hair conditioners

In the 1950s,

alkoxy ammonium salts.[28]

  • Cationic surfactants used as fabric softeners
  • Distearyldimethylammonium chloride, an early generation fabric softener with low biodegradability that was phased out.
    biodegradability
    that was phased out.
  • Another diesterquat, a contemporary fabric softener.
    Another diesterquat, a contemporary fabric softener.
  • Diethyl ester dimethyl ammonium chloride used as a fabric softener.
    Diethyl ester dimethyl ammonium chloride used as a fabric softener.
  • Another diesterquat used as a fabric softener.
    Another diesterquat used as a fabric softener.

The antistatic qualities that make quaternary ammonium salts useful as fabric softeners also make them useful in hair conditioners and shampoos.[29] The idea was pioneered by Henkel with a 1984 patent.[30] Examples include cetrimonium chloride and behentrimonium chloride.[31]

Plant growth retardants

Cycocel (chlormequat chloride) reduces plant height by inhibiting the production of gibberellins, the primary plant hormones responsible for cell elongation. Therefore, their effects are primarily on stem, petiole, and flower stalk tissues. Lesser effects are seen in reductions of leaf expansion, resulting in thicker leaves with darker green color.[32]

Natural occurrence

Several quaternary ammonium derivatives exist in nature.

glycine betaine, choline, carnitine. butyrobetaine, homarine, and trigonelline. Glycine betaine, an osmolyte, stabilizes osmotic pressure in cells.[34]

Glycine betaine is a naturally occurring quaternary ammonium cation. Its degradation product, trimethylamine
, is responsible for the odor of spoiled fish.
Choline is a quat compound.

Choline is a precursor for the neurotransmitter

phosphatidylcholines, a major component of biological membranes, are a member of the lecithin group of fatty substances in animal and plant tissues.[36]

beta-oxidation of fatty acids.[citation needed
]

1-Oleoyl-2-palmitoyl-phosphatidylcholine

Health effects

Quaternary ammonium compounds can display a range of health effects, amongst which are mild skin and respiratory irritation [37] up to severe caustic burns on skin and the gastrointestinal wall (depending on concentration), gastrointestinal symptoms (e.g., nausea and vomiting), coma, convulsions, hypotension and death.[38]

They are thought to be the chemical group responsible for

neuromuscular blocking drugs during general anaesthesia in surgery.[39] Quaternium-15 is the single most often found cause of allergic contact dermatitis of the hands (16.5% in 959 cases).[40]

Possible reproductive effects in laboratory animals

Quaternary ammonium-based disinfectants (Virex and Quatricide) were tentatively identified as the most probable cause of jumps in birth defects and fertility problems in caged lab mice. The quat ingredients in the disinfectants include alkyl dimethyl benzyl ammonium chloride (ADBAC) and didecyl dimethyl ammonium chloride (DDAC).[41][42] A similar link was tentatively identified in nurses.[43] The studies contradict earlier toxicology data reviewed by the U.S. Environmental Protection Agency (U.S. EPA) and the EU Commission.[44]

Quantification

The

ESI-MS and NMR spectroscopy.[4]

See also

References

  1. doi:10.1351/goldbook.Q05003
  2. ISSN 0362-4331
    . Retrieved 2022-02-17.
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    PMID 15285677
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  4. ^
    ISBN 0471238961
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  5. doi:10.15227/orgsyn.034.0058
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  6. ISBN 0-471-58589-0
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  7. ISBN 978-3527306732
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  8. PMID 25431246
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  9. doi:10.1021/ed054p229.1
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  10. doi:10.1021/ed057p308.1
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  11. ^ Brasen WR, Hauser CR (1963). "2-Methylbenzyldimethylamine". Organic Syntheses; Collected Volumes, vol. 4, p. 585.
  12. ISBN 978-0471264187
    .
  13. ISBN 9783527306732
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  14. ^ "Quats applications". 22 October 2021.
  15. ^ Lim XZ (August 2, 2020). "Do we know enough about the safety of quat disinfectants?". Chemical and Engineering News. Retrieved 2023-01-08.
  16. PMC 7341688
    .
  17. ISBN 978-3527306732
    .
  18. PMID 11423105
    .
  19. ^ Abedon ST. "Specific Antimicrobials". Ohio State University. Archived from the original on 2008-10-15. Retrieved 2020-02-14.
  20. PMID 32412231
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  21. PMID 26345999
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  22. ^
    S2CID 26326417
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  24. PMID 22287007
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  25. ISBN 978-3527306732
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  26. S2CID 195343430
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  27. ^ "Henkel Consumer Info". Henkelconsumerinfo.com. Archived from the original on 2019-10-18. Retrieved 2009-06-04.
  28. ISBN 978-3527306732
    .
  29. ^ Distearyldimonium chloride in the Consumer Product Information Database
  30. ^ "Quaternary ammonium compound hair conditioners US4744977". Google Patents. 14 November 1985.
  31. ^ "What is cetrimonium chloride?". naturallycurly.com. November 2007. Archived from the original on 2012-03-04.
  32. ^ "Growth Retardants". Archived from the original on September 25, 2011. Retrieved July 19, 2012. Wageningen Agricultural University, The Netherlands
  33. doi:10.1016/0305-0491(91)90002-U
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  34. PMID 25564467
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  35. PMID 19906248
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  36. ISBN 0-444-89321-0
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  37. PMID 19327131
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  38. ^ "Quaternary ammonium". Internationally Peer Reviewed Chemical Safety Information (INCHEM). World Health Organization. PIM G022.
  39. PMID 19143700
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  40. PMID 17553593
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  41. PMID 18563110
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  44. ^ Office of Prevention, Pesticides and Toxic Substances, US EPA (August 2006). "Reregistration Eligibility Decision for Aliphatic Alkyl Quaternaries (DDAC)". Epa739-R-06-008.

Further reading

  • Zhang C, Cui F, Zeng GM, Jiang M, Yang ZZ, Yu ZG, et al. (June 2015). "Quaternary ammonium compounds (QACs): a review on occurrence, fate and toxicity in the environment". The Science of the Total Environment. 518–519: 352–362.
    PMID 25770948
    .

External links
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