A
foiled carbene in
organic chemistryOrganic chemistry is a discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation of chemical compounds that contain carbon...
is a special type of stabilized
carbeneIn chemistry, a carbene is a organic molecule containing a carbon atom with six valence electrons and having the general formula RR'C:. Carbenes are classified into two varieties, singlets and triplets. Most carbenes are very short lived, although persistent carbenes are known.The prototypical...
due to the proximity of a
double bondA double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons instead of the usual two. The most common double bond, that between two carbon atoms, can be found in alkenes. Many types of double bonds between two different elements exist, for example in...
. This type of reactive intermediate is implicated in certain
organic reactionOrganic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions and redox reactions. In organic synthesis, organic reactions are used...
s. The positive interaction between carbene and double bond is only present in the singlet type and based on through-space electron transfer between the empty carbene p-orbital (
LUMOLumo is a 2007 documentary film about twenty-year-old Lumo Sinai, a woman who fell victim to "Africa's First World War." While returning home one day, Lumo and another woman were gang-raped by a group of soldiers fighting for control of the Democratic Republic of the Congo during the 1994 Rwandan...
) and filled alkene double bond p-orbitals (
HOMO-Science:*Homo , the genus including modern humans and closely related species such as Neanderthals*Highest Occupied Molecular Orbital, in chemistry: see HOMO/LUMO-Organisations:...
).
A
foiled carbene in
organic chemistryOrganic chemistry is a discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation of chemical compounds that contain carbon...
is a special type of stabilized
carbeneIn chemistry, a carbene is a organic molecule containing a carbon atom with six valence electrons and having the general formula RR'C:. Carbenes are classified into two varieties, singlets and triplets. Most carbenes are very short lived, although persistent carbenes are known.The prototypical...
due to the proximity of a
double bondA double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons instead of the usual two. The most common double bond, that between two carbon atoms, can be found in alkenes. Many types of double bonds between two different elements exist, for example in...
. This type of reactive intermediate is implicated in certain
organic reactionOrganic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions and redox reactions. In organic synthesis, organic reactions are used...
s. The positive interaction between carbene and double bond is only present in the singlet type and based on through-space electron transfer between the empty carbene p-orbital (
LUMOLumo is a 2007 documentary film about twenty-year-old Lumo Sinai, a woman who fell victim to "Africa's First World War." While returning home one day, Lumo and another woman were gang-raped by a group of soldiers fighting for control of the Democratic Republic of the Congo during the 1994 Rwandan...
) and filled alkene double bond p-orbitals (
HOMO-Science:*Homo , the genus including modern humans and closely related species such as Neanderthals*Highest Occupied Molecular Orbital, in chemistry: see HOMO/LUMO-Organisations:...
). The result is a
three-center two-electron bondA three-center two-electron bond is an electron deficient chemical bond where three atoms share two electrons. The combination of three atomic orbitals form three molecular orbitals: one bonding, one non-bonding, and one anti-bonding. The two electrons go into the bonding orbital, resulting in a...
akin certain
non-classical ionNon-classical ions in organic chemistry are a special type of carbonium ions displaying delocalization of sigma bonds in 3-center-2-electron bonds of bridged systems. The term non-classical ion was first used by J.D...
s.
The increased stabilization blocks certain otherwise ordinary reaction modes for the carbene hence the term
foiled. An example is
norbornen-7-ylidene which is
norborneneNorbornene or norbornylene or norcamphene is a bridged cyclic hydrocarbon. It is a white solid with a pungent sour odor. The molecule consists of a cyclohexene ring bridged with a methylene group in the para position...
with a carbenic carbon atom at the bridge position.
In silicoIn silico is an expression used to mean "performed on computer or via computer simulation." The phrase is coined in analogy to the Latin phrases in vivo and in vitro which are commonly used in biology and refer to experiments done in living organisms and outside of living organisms, respectively...
experiments reveal that the bridge in this molecule is actually bending towards the double bond with an optimum angle of around 90° vs 130° for norbornene .