In
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 ...
, vinylidenes are compounds with the
functional group
In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest ...
C=CH
2. An example is
1,1-dichloroethene
1,1-Dichloroethene, commonly called 1,1-dichloroethylene or vinylidene chloride or 1,1-DCE, is an organochloride with the molecular formula CHCl. It is a colorless liquid with a sharp odor. Like most chlorocarbons, it is poorly soluble in water, ...
(CCl
2=CH
2) commonly called ''vinylidene chloride''. It and
vinylidene fluoride
1,1-Difluoroethylene, also known as vinylidene fluoride, is a hydrofluoroolefin. It is a flammable gas. Global production in 1999 was approximately 33,000 metric tons. It is primarily used in the production of fluoropolymers such as polyvinyliden ...
are precursors to commercially useful polymers.
Monomers and polymers
Vinylidene chloride and fluoride can be converted to linear polymers
polyvinylidene chloride
Polyvinylidene chloride, or polyvinylidene dichloride (PVDC), is a homopolymer of vinylidene chloride.
History
Ralph Wiley accidentally discovered polyvinylidene chloride polymer in 1933. He, then, was a college student who worked part-time at D ...
(PVDC) and
polyvinylidene fluoride
Polyvinylidene fluoride or polyvinylidene difluoride (PVDF) is a highly non-reactive thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride.
PVDF is a specialty plastic used in applications requiring the highest pur ...
(PVDF). The polymerization reaction is:
: ''n'' CH
2=CX
2 → (CH
2−CX
2)
''n''
These vinylidene polymers are
isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers.
Iso ...
ic with those produced from
vinylene monomers. Thus polyvinylene fluoride from vinylene fluoride (HFC=CHF).
Vinylidene complexes
Although vinylidenes are only transient species, they are found as
ligand
In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electr ...
s in
organometallic chemistry
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
. They typically arise by the protonation of metal
acetylide
In organometallic chemistry, acetylide refers to chemical compounds with the chemical formulas and , where M is a metal. The term is used loosely and can refer to substituted acetylides having the general structure (where R is an organic side c ...
s or by the reaction of metal electrophiles with terminal alkynes. The complex
chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium
Chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium is the organoruthenium half-sandwich compound with formula RuCl(PPh3)2(C5H5). It as an air-stable orange crystalline solid that is used in a variety of organometallic synthetic and cataly ...
readily forms such complexes:
:CpRu(PPh
3)
2Cl + RC
2H + KPF
6 →
pRu(PPh3)2(=C=C(H)PhF
6 + KCl
Gas-phase existence of vinylidenes
Featuring
divalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules.
Description
The combining capacity, or affinity of an ...
carbon, vinylidenes are unusual species in organic chemistry. They are unstable as solids or liquids but can be generated as stable dilute gases. The parent member of this series is
methylidenecarbene. With the formula :C=CH
2), it is a
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 ...
.
IUPAC nomenclature
In IUPAC nomenclature, 1,1-ethenediyl describes the connectivity >C=CH
2. The related species ethenylidenes have the connectivity =C=CH
2.
See also
*
Vinylene group, −CH=CH−
*
Methylene group
In organic chemistry, a methylene group is any part of a molecule that consists of two hydrogen atoms bound to a carbon atom, which is connected to the remainder of the molecule by two single bonds. The group may be represented as , where the '< ...
, −CH
2−
*
Vinyl group
In organic chemistry, a vinyl group (abbr. Vi; IUPAC name: ethenyl group) is a functional group with the formula . It is the ethylene (IUPAC name: ethene) molecule () with one fewer hydrogen atom. The name is also used for any compound contain ...
, −CH=CH
2
References
{{reflist
Functional groups