Lewis Acid/Base Interaction Matrix Database

Onium Ion Lewis Acids

Hypervalent Molecular Cations

Search for onium ion Lewis acid species in The Chemical Thesaurus

FMO Topology:

The onium ion Lewis acids have a central electronegative atom saturated with Lewis acid "ligands", usually H+ or alkyl+.

Onium ion Lewis acids are all proton/X Lobe-HOMO or carbenium ion/X Lobe-HOMO complexes where:

X = N, O, F, Ne, P, S, Cl, Ar, As, Se, Br, Kr, Sb, Te, I, Xe

Charge: Positive
HSAB: Intrinsically hard, but species behave as a source of hard H+ or the relatively soft Lobe-LUMO Lewis acid carbenium ion, H3C+.
Chemistry:

Onium ions either form charge-controlled (ionic) complexes or they react by transferring a ligand to a nucleophilic /basic Lewis base.

If the transferred ligand is H+, the onium ion acts as a Brønsted Acid.

If the transferred ligand is a carbenium ion Lewis acid, the onium ion is said to be an alkylating agent.

High symmetry tetraalkyl ammonium ions, such as [(CH3)4N]+, can act as spectator cations.

Methane can be protonated to the five valent carbonium ion: [CH5]+

Second order nucleophilic substitution reactions at carbon pass through a five valent carbonium ion transition state:

Congeneric Series:

There is one onium ion Lewis acid planar:

Ammonium, phosphonium, oxonium and sulfonium ions give rise to many ligand replacement congeneric series, for example:

[R4N]+   [R3NR']+   [R2NR2]+   [RNR'3]+   [NR'4]+

where R and/or R' = H, CH3, alkyl, C6H5 etc.

Onium ion Lewis acid (generic)
Aldehyde, protonated (generic)

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Alkyl alkoxy hydroxy carbenium ion (generic)

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Alkyl oxonium ion (generic)

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1° Alkyl oxonium ion (generic)

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Alkyl telluronium ion (generic)

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Amide, protonated (generic)

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Ammonium ion

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1° Ammonium ion (generic)

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2° Ammonium ion (generic)

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3° Ammonium ion (generic)

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4° Ammonium ion (generic)

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Aqueous mineral acid, 0.05 to 1.0 molar (generic)

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Argonium ion

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Aronium ion (generic)

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Arsonium ion

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Arsonium ion (generic)

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Benzene diazonium ion

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Benzonium ion

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Brønsted acid, oxonium (generic)

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Bromonium ion

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tertiary Butyl oxonium ion

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Carbenium ion, beta-amino (generic)

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Carbenium ion, beta-ether (generic)

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Carbenium ion, beta-thioether (generic)

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Carbonium ion

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Carboxylic acid, protonated (generic)

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Chloronium ion

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Chloronium ion, alkyl (generic)

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Dialkyl oxonium ion (generic)

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Dialkyl telluronium ion (generic)

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Dialkylhydroxy carbenium ion (generic)

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Diazonium ion (generic)

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Difluorochloronium ion

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Dihydroxymethyl carbenium ion

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Dimethyl sulfonium ion

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Dimethylammonium ion

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Dimethylformamide, protonated

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Dimethylhydroxy carbenium ion

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Dimethyloxonium ion

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Dimethylsulfoxide, protonated

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Diphenylammonium ion

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Duteronium ion

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Eigen Cation

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Ethenyl bromonium ion

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Ethylacetate, protonated

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Ethylbenzene SeAr intermediate

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Fluoronium ion

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Fluoronium ion, alkyl (generic)

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Guanidine, protonated

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Hydrazinium ion

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Hydronium ion, [H3]+

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Hydroxy acid, protonated (generic)

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Hydroxy carbenium ion

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Hydroxyammonium ion

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Hydroxydialkoxy carbenium ion (generic)

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Hydroxymethyl carbenium ion

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Imidazonium ion

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Iodonium ion

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Iodonium ion, alkyl (generic)

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Isopropyl oxonium ion

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Kryptonium ion

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Methylammonium ion

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Methyloxonium ion

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Methylsulfonium ion

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Methyltriethylammonium ion

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Neonium ion

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Nitric acid, protonated

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Nitrilium ion (generic)

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Nitrobenzene SeAr intermediate

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Nitrobenzene, protonated

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Nitromethane, protonated

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Oxonium ion

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Phenyl ammonium ion (generic)

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Phenylammonium ion

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Phenylethanone SeAr intermediate

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Phenyloxonium ion

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Phosphonium ion

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Phosphonium ion (generic)

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Phosphonium ion, alkyl triphenyl (generic)

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Protonated base, [H-B]+ (generic)

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Pyridinium ion

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Pyrylium ion

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Selenonium ion

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Stibonium ion

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Sulfonium ion

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Sulfonium ion, alkyl (generic)

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Sulfonium ion, dialkyl (generic)

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Telluronium ion

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Tetrahydrofuran, protonated

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Tetramethylammonium ion

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Thiocarbenium ion (generic)

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Thiopyrylium ion

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Trialkyloxonium ion (generic)

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Trialkylsulfonium ion (generic)

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Triethylarsonium ion

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Trimethylammonium ion

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Trimethyloxonium ion

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Trimethylphosphonium ion

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Trimethylsulfonium ion

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Trimethylsulfoxonium iodide

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Trimethylsulfoxonium ion

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Triphenyloxonium ion

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Urea, protonated

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Xenon fluoride cation

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Xenon, protonated

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Ylid (generic)

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Zundel cation

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Poster
Nucleophiles & Bases

© Mark R. Leach 1999-


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