chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...

, a Verkade base (or Verkade superbase) is a

superbase A superbase is a compound that has a particularly high affinity for protons. Superbases are of theoretical interest and potentially valuable in organic synthesis. Superbases have been described and used since the 1850s.''Superbases for Organic ...

with the formula P(MeNCH₂CH₂)₃N. A colorless oil, it is an

aminophosphine In organophosphorus chemistry, an aminophosphine is a compound with the formula R3−nP(NR2)n where R = H or an organic substituent, and n = 0, 1, 2. At one extreme, the parent H2PNH2 is lightly studied and fragile, but at the other extreme tris(di ...

although its inventor John Verkade called it proazaphosphatrane. The trimethyl derivative or 2,5,8,9-tetraza-1-phosphabicyclo .3.3ndecane is the simplest. Diverse analogues of the Verkade base are known, e.g. with

isopropyl group In organic chemistry, propyl is a three-carbon alkyl substituent with chemical formula for the linear form. This substituent form is obtained by removing one hydrogen atom attached to the terminal carbon of propane. A propyl substituent is ofte ...

s in place of methyl.

Synthesis and reactions

The Verkade base is generated by the reaction of N,N,N-trimethyl

tren Tren may mean: *Tris(2-aminoethyl)amine, a coordination chemistry compound *Trenbolone, a veterinary steroid * ''Tren'', a 1978 Yugoslav film See also *train In rail transport, a train (from Old French , from Latin , "to pull, to draw") is ...

with

tris(dimethylamino)phosphine Tris(dimethylamino)phosphine is an organophosphorus compound with the formula P(NMe2)3 (Me = methyl). It is a colorless oil at room temperature, and is one of the most common aminophosphines. Its structure has been determined by X-ray crystallog ...

: :P(NMe₂)₃ + (MeNHCH₂CH₂)₃N → P(MeNCH₂CH₂)₃N + 3 Me₂NH The principal reaction of the Verkade base is

protonation In chemistry, protonation (or hydronation) is the adding of a proton (or hydron, or hydrogen cation), (H+) to an atom, molecule, or ion, forming a conjugate acid. (The complementary process, when a proton is removed from a Brønsted–Lowry acid, ...

. The proton is attacked by the Verkade base at phosphorus, which induces the formation of a

transannular In organic chemistry annulation (from the Latin ''anellus'' for "little ring"; occasionally annelation) is a chemical reaction in which a new ring is constructed on a molecule. : Examples are the Robinson annulation, Danheiser annulation and cert ...

P-N bond. The product exemplifies the structure of an

atrane Atranes are a class of tricyclic molecules with three five-membered rings. It is a heterocyclic structure similar to the propellanes. It has a transannular dative bond from a nitrogen at one bridgehead to a Lewis acidic atom such as silicon or bor ...

. 290 px, left, Protonation of Verkade base. The

conjugate acid A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a ...

P(MeNCH₂CH₂)₃Nsup>+ has a pK_a of 32.9 in

acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not clas ...

. For comparison, the conjugate acid of

triethylamine Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. It is also abbreviated TEA, yet this abbreviation must be used carefully to avoid confusion with triethanolamine or tetraethylammonium, for which TEA ...

has a pK_a near 17 in acetonitrile. Owing to its ability to

deprotonate Deprotonation (or dehydronation) is the removal (transfer) of a proton (or hydron, or hydrogen cation), (H+) from a Brønsted–Lowry acid in an acid–base reaction.Henry Jakubowski, Biochemistry Online Chapter 2A3, https://employees.csbsju.edu ...

weak carbon acids, the Verkade base catalyzes a variety of

condensation reaction In organic chemistry, a condensation reaction is a type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a ...

Related compounds

Phosphazenes Phosphazenes refer to classes of organophosphorus compounds featuring phosphorus(V) with a double bond between P and N. One class of phosphazenes have the formula . These phosphazenes are also known as iminophosphoranes and phosphine imides. They ar ...

are phosphorus(V) derivatives with the formula RN=P(NR₂)₃.

References

{{Organophosphorus Amides Organophosphanes Quaternary ammonium compounds Superbases Atranes