Hemicucurbituril
Encyclopedia
A hemicucurbituril is a macrocycle
composed of alternating units of methylene
and N-substituted ethylene urea units. Hemicucurbit[6]uril is a hexamer
. This compound closely resembles cucurbituril
cut in half along the equator and the chemistry is also similar. The ethylene urea units also alternate with the carbonyl
groups assuming alternating up and down positions. For this reason this compound contrary to cucurbituril is unable to form inclusion compound
s with metal ions.
The compound is formed by reaction of ethylene urea with a 37% solution of formalin and hydrochloric acid
in a sequence of Mannich reaction
s . The success of the reaction critically depends on the acid concentration, which is why the discovery of the compound took until 2004. A crystalline product settles out of the solution which is the inclusion compound
of Hemicucurbituril with water or HCl. These guests can be driven out by application of elevated temperature and a vacuum. With tweaking of the reaction conditions the hemicucurbit[12]uril (n = 6) is also obtained.
Macrocycle
A macrocycle is, as defined by IUPAC, "a cyclic macromolecule or a macromolecular cyclic portion of a molecule." In the chemical literature, organic chemists may consider any molecule containing a ring of nine or more atoms to be a macrocycle...
composed of alternating units of methylene
Methylene
Methylene is a chemical species in which a carbon atom is bonded to two hydrogen atoms. Three different possibilities present themselves:* the -CH2- substituent group: e.g., dichloromethane ....
and N-substituted ethylene urea units. Hemicucurbit[6]uril is a hexamer
Hexamer
A hexamer is a thing composed out of six sub-units.In microbiology, a hexamer is one of the proteins composing the polyhedral protein shell that encloses the bacterial micro-compartments known as carboxysomes....
. This compound closely resembles cucurbituril
Cucurbituril
Cucurbiturils are methylene-linked macrocyclic molecules made of glycoluril [=C4H2N4O2=] monomers. The oxygen atoms are located along the edges of the band and are tilted inwards, forming a partly enclosed cavity...
cut in half along the equator and the chemistry is also similar. The ethylene urea units also alternate with the carbonyl
Carbonyl
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups....
groups assuming alternating up and down positions. For this reason this compound contrary to cucurbituril is unable to form inclusion compound
Inclusion compound
In host-guest chemistry an inclusion compound is a complex in which one chemical compound forms a cavity in which molecules of a second "guest" compound are located. The definition of inclusion compounds is very broad, extending to channels formed between molecules in a crystal lattice in which...
s with metal ions.
The compound is formed by reaction of ethylene urea with a 37% solution of formalin and hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
in a sequence of Mannich reaction
Mannich reaction
The Mannich reaction is an organic reaction which consists of an amino alkylation of an acidic proton placed next to a carbonyl functional group with formaldehyde and ammonia or any primary or secondary amine. The final product is a β-amino-carbonyl compound also known as a Mannich base...
s . The success of the reaction critically depends on the acid concentration, which is why the discovery of the compound took until 2004. A crystalline product settles out of the solution which is the inclusion compound
Inclusion compound
In host-guest chemistry an inclusion compound is a complex in which one chemical compound forms a cavity in which molecules of a second "guest" compound are located. The definition of inclusion compounds is very broad, extending to channels formed between molecules in a crystal lattice in which...
of Hemicucurbituril with water or HCl. These guests can be driven out by application of elevated temperature and a vacuum. With tweaking of the reaction conditions the hemicucurbit[12]uril (n = 6) is also obtained.