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

Polar effect

The Polar effect or electronic effect in chemistry is the effect exerted by a substituent on modifying electrostatic forces operating on a nearby reaction center...

 substituent

Substituent

In organic chemistry and biochemistry, a substituent is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon...

 on one side of the double bond

Double bond

A 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...

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

Pi bond

In chemistry, pi bonds are covalent chemical bonds where two lobes of one involved atomic orbital overlap two lobes of the other involved atomic orbital...

 very polarized

Polarizability

Polarizability is the measure of the change in a molecule's electron distribution in response to an applied electric field, which can also be induced by electric interactions with solvents or ionic reagents. It is a property of matter...

. The rotational barrier for a push-pull olefin is lower than that of an ordinary olefin and this makes it an interesting candidate for a molecular switch

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 changes in e.g. pH, light, temperature, an electrical current, microenvironment, or the presence of a ligand. In some cases, a...

 for instance azobenzene

Azobenzene

Azobenzene is a chemical compound composed of two phenyl rings linked by a N=N double bond. It is the best known example of an azo compound. The term 'azobenzene' or simply 'azo' is often used to refer to a wide class of molecules that share the core azobenzene structure, with different chemical...

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

Cyclobutadiene is the smallest [n]-annulene , an extremely unstable hydrocarbon having a lifetime shorter than five seconds in the free state. It has chemical formula 44 and a rectangular structure verified by infrared studies. This is in contrast to the square geometry predicted by simple Hückel...

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

Ester

Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

 substituents and two tertiary amine substituents) the molecule is stable indeed.

See also

• Leimgruber–Batcho indole synthesis
• Application of push–pull olefins in molecular logic gate
  Molecular logic gate
  A molecular logic gate is a molecule that performs a logical operation on one or more logic inputs and produces a single logic output. Much academic research is dedicated to the development of these systems and several prototypes now exist...
  
  s