In
chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...
, vinylidenes are compounds with the
functional group
In organic chemistry, a functional group is any substituent or moiety (chemistry), moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions r ...
C=CH
2. An example is
1,1-dichloroethene
1,1-Dichloroethylene, commonly called vinylidene chloride or 1,1-DCE, is an organochloride with the molecular formula . It is a colorless liquid with a sharp odor. Like most chlorocarbons, it is poorly soluble in water but soluble in organic solv ...
(CCl
2=CH
2) commonly called ''vinylidene chloride''. It and
vinylidene fluoride 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. At the time he was a college student who worked part-t ...
(PVDC) and
polyvinylidene fluoride
Polyvinylidene fluoride or polyvinylidene difluoride (PVDF) is a highly non-reactive thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride. Its chemical formula is (C2H2F2)''n''.
PVDF is a specialty plastic use ...
(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 formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...
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 with a 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 el ...
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 chemistry, an acetylide is a compound that can be viewed as the result of replacing one or both hydrogen atoms of acetylene (ethyne) by metallic or other cations. Calcium carbide is an important industrial compound, which has long been used ...
s or by the reaction of metal electrophiles with terminal alkynes. The complex
chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium 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 atom is a measure of its combining capacity with other atoms when it forms chemical compounds or molecules. Valence is generally understood to be the number of chemica ...
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 (chemistry), valence of two and two unshared valence electrons. The general formula is or where the R represents substituents or hydrogen atoms.
Th ...
.
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
A methylene group is any part of a molecule that consists of two hydrogen atoms bound to a carbon
Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—m ...
, −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 contai ...
, −CH=CH
2
References
{{reflist
Functional groups