Amine oxide

As the amine, more amine N- oxide, a group is called chemical compounds containing the functional group R3N - O - sometimes referred to as R3N → O (formerly also, however, wrong, R3N = O) written - contains. Amine oxides exist as derivatives of tertiary aliphatic amines and aromatic nitrogen compounds, such as pyridine.

Properties

Amine oxides are highly polar and therefore often solids. Amine oxides with smaller molar mass are very good in water and sparingly soluble in nonpolar organic solvents.

Amine oxides are weak bases having a pKa value of about 4.5. The corresponding acid is R3N -OH.

Amine oxides, with three different alkyl groups are optically active, as opposed to the underlying amines, no inversion ( inversion of the configuration) is also possible.

Occurrence

Amine oxides may be found as an osmolyte and as products of oxidation of tertiary amines in nature. Thus, for example, containing per kg meat of sea fish 40 to 120 mg of trimethylamine N- oxide ( TMAO ). After the death of the animals is is broken down by bacteria to trimethylamine, which causes the typical unpleasant fishy odor.

Production

Amine oxides are prepared by oxidation of the corresponding amines with hydrogen peroxide or peracids ( such as meta -chloroperbenzoic acid, peracetic acid, peroxymonosulphuric acid ).

Use

Amine N-oxides are used as protective group of amines, as a synthetic intermediate, as an oxidizing agent (e.g., N -methylmorpholine- N-oxide), or the modulation of the electron distribution in the aromatic nitrogen-containing compounds in electrophilic substitution application. Amine oxides with a long-and two short-chain alkyl groups such as N-dodecyl- N, N -dimethylamine C12H25 (CH3) 2NO be used as surfactants.

Amine oxides can be used for titration of the carbon -boron bonds, and for the regeneration of L- selectride hydroborations and reductions.

Reactions

  • Pyrolytic elimination of amine oxides when heated to 150 to 200 ° C - called the Cope elimination.
  • Reduction to the amine with lithium aluminum hydride, sodium borohydride, catalytic hydrogenation, zinc or iron and acetic acid and phosphorus trichloride.
  • Pyridine- N-oxides can be alkylated with electrophiles to the ring.
  • The Meisenheimer rearrangement for the production of O- alkylhydroxylamines.
  • Cleavage of amine oxides with acetic anhydride to give the acetamides and formaldehyde ( Polonovski reaction)
Enantiomer Protecting group N-Methylmorpholine N-oxide L-selectride Cope reaction
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