Imidazolidine is a
heterocyclic compound
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...
(CH
2)
2(NH)
2CH
2. The parent imidazolidine is lightly studied, but related compounds substituted on one or both nitrogen centers are more common. Generally, they are colorless, polar, basic compounds. Imidazolidines are cyclic 5-membered examples of the general class of
aminal
In organic chemistry, an aminal or aminoacetal is a functional group or type of organic compound that has two amine groups attached to the same carbon atom: . (As is customary in organic chemistry, R can represent hydrogen or an alkyl group). A ...
s.
Preparation
Imidazolidines are traditionally prepared by
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 ...
of 1,2-
diamine
A diamine is an amine with exactly two amino groups. Diamines are used as monomers to prepare polyamides, polyimides, and polyureas. The term ''diamine'' refers mostly to primary diamines, as those are the most reactive.
In terms of quantities p ...
s and
aldehyde
In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...
s. Most commonly, one or both nitrogen center is substituted with an alkyl or
benzyl
In organic chemistry, benzyl is the substituent or molecular fragment possessing the structure . Benzyl features a benzene ring () attached to a methylene group () group.
Nomenclature
In IUPAC nomenclature, the prefix benzyl refers to a substi ...
(Bn) group:
[Ferm, R. J.; Riebsomer, J. L. From "The chemistry of the 2-imidazolines and imidazolidines" Chemical Reviews, 1954, 54, 593-613. ]
:(CH
2NBn)
2 + PhCHO → (CH
2NBn)
2C(H)Ph + H
2O
The first unsubstituted imidazolidine synthesis was reported in 1952.
Reactions
Unsubstituted imidazolidines are often labile.
The rings are susceptible to hydrolysis back to the diamine and the aldehyde.
[
Formally, removal of the two hydrogens at carbon 2 (between the two nitrogens) would yield the ]carbene
In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is or where the R represents substituents or hydrogen atoms.
The term "carbene" ma ...
dihydroimidazol-2-ylidene
Dihydroimidazol-2-ylidene is a hypothetical organic compound with formula C3H6N2. It would be a heterocyclic compound, formally derived from imidazolidine with two hydrogen atoms removed from carbon number 2, leaving two vacant chemical bonds — ...
. Derivatives of the latter comprise an important class of persistent carbene
A persistent carbene (also known as stable carbene) is a type of carbene demonstrating particular stability. The best-known examples and by far largest subgroup are the ''N''-heterocyclic carbenes (NHC) (sometimes called Arduengo carbenes), for ex ...
s.
Related imidazole-derived heterocycles
Classified as a diamine
A diamine is an amine with exactly two amino groups. Diamines are used as monomers to prepare polyamides, polyimides, and polyureas. The term ''diamine'' refers mostly to primary diamines, as those are the most reactive.
In terms of quantities p ...
, it is formally derived by the addition of four hydrogen atoms to imidazole
Imidazole (ImH) is an organic compound with the formula C3N2H4. It is a white or colourless solid that is soluble in water, producing a mildly alkaline solution. In chemistry, it is an aromatic heterocycle, classified as a diazole Diazole refers ...
. The intermediate, resulting from the addition of only two hydrogen atoms is called imidazoline
Imidazoline is a class of heterocycles formally derived from imidazoles by the reduction of one of the two double bonds. Three isomers are known, 2-imidazolines, 3-imidazolines, and 4-imidazolines. The 2- and 3-imidazolines contain an imine
In ...
(dihydroimidazole). The connection of imidazolidine to related compounds is indicated in the Figure.
References
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