A push-pull olefin is a type of olefin characterized by an

electron-withdrawing In chemistry, an electron-withdrawing group (EWG) is a substituent that has some of the following kinetic and thermodynamic implications: *with regards to electron transfer, electron-withdrawing groups enhance the oxidizing power tendency of th ...

substituent on one side of the

double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betwee ...

and an electron-donating substituent on the other side. This makes the

pi bond In chemistry, pi bonds (π bonds) are covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally. Each of these atomic orbitals ...

very polarized. The

rotational barrier In chemistry, conformational isomerism is a form of stereoisomerism in which the isomers can be interconverted just by rotations about formally single bonds (refer to figure on single bond rotation). While any two arrangements of atoms in a mo ...

for a push-pull olefin is lower than that of an ordinary olefin and this makes it an interesting candidate for a

molecular switch A molecular switch is a molecule that can be reversibly shifted between two or more stable states. The molecules may be shifted between the states in response to environmental stimuli, such as changes in pH, light, temperature, an electric curren ...

, for instance

azobenzene Azobenzene is a photoswitchable chemical compound composed of two phenyl rings linked by a N=N double bond. It is the simplest example of an aryl azo compound. The term 'azobenzene' or simply 'azo' is often used to refer to a wide class of simi ...

s. A push-pull configuration also helps to stabilize the double bond because the carbon-carbon bond has considerably less double bond character. For instance,

cyclobutadiene Cyclobutadiene is an organic compound with the formula . It is very reactive owing to its tendency to dimerize. Although the parent compound has not been isolated, some substituted derivatives are robust and a single molecule of cyclobutadiene is ...

is a very unstable molecule but with both olefinic bonds in push-pull configuration (two

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides a ...

substituents and two

tertiary amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such ...

substituents) the molecule is stable indeed.

References

* ''Ethyl (2-cyano-3-ethoxyacryloyl)carbamate: irreversible thermal isomerization of a push-pull olefin'' Kuangsen Sung, Ming-Chi Lin, Pin-Mei Huang, Bo-Ren Zhuang, Robert Sung,Ru-Rong Wu

Arkivoc ''Arkivoc'' (''Archive for Organic Chemistry'') is a peer-reviewed open access scientific journal covering all aspects of organic chemistry. It is published by the non-profit organization Arkat USA, which was established in 2000 through a personal ...

2005 p. 13

open access (publishing), open access publication

References

See also