4-Cyano-4'-pentylbiphenyl
Encyclopedia
4-Cyano-4'-pentylbiphenyl is a commonly used nematic liquid crystal
with the chemical formula C18H19N. It frequently goes by the common name 5CB. 5CB was first synthesized by George William Gray
, Ken Harrison, and J.A. Nash at the University of Hull
in 1972 and at the time it was the first member of the cyanobiphenyls. The liquid crystal was discovered after Gray's group received a grant from the UK Ministry of Defence
to find a liquid crystal that had liquid crystal phases near room temperature with the specific intention of using them in liquid crystal displays. The molecule is about 20 Å long. The liquid crystal 5CB undergoes a phase transition from a crystalline state to a nematic state at 18 °C and it goes from a nematic to an isotropic state at 35 °C.
is added to the biphenyl to introduce a Bromine atom to the end of the moiety. Next aluminium chloride
and
is added to the sample, followed by the addition of potassium hydroxide
and
. By this point the molecule will have a bromine atom on one end of the rigid core and 
on the other end. The introduction of copper(I) cyanide
and DMF results in the removal of the bromine and its replacement with CN. This is the final step in the production of 5CB.
Liquid crystal
Liquid crystals are a state of matter that have properties between those of a conventional liquid and those of a solid crystal. For instance, an LC may flow like a liquid, but its molecules may be oriented in a crystal-like way. There are many different types of LC phases, which can be...
with the chemical formula C18H19N. It frequently goes by the common name 5CB. 5CB was first synthesized by George William Gray
George William Gray
George William Gray CBE, FRS is a Professor of Organic Chemistry at the University of Hull who was instrumental in developing the long-lasting materials which made liquid crystal displays possible...
, Ken Harrison, and J.A. Nash at the University of Hull
University of Hull
The University of Hull, known informally as Hull University, is an English university, founded in 1927, located in Hull, a city in the East Riding of Yorkshire...
in 1972 and at the time it was the first member of the cyanobiphenyls. The liquid crystal was discovered after Gray's group received a grant from the UK Ministry of Defence
Ministry of Defence (United Kingdom)
The Ministry of Defence is the United Kingdom government department responsible for implementation of government defence policy and is the headquarters of the British Armed Forces....
to find a liquid crystal that had liquid crystal phases near room temperature with the specific intention of using them in liquid crystal displays. The molecule is about 20 Å long. The liquid crystal 5CB undergoes a phase transition from a crystalline state to a nematic state at 18 °C and it goes from a nematic to an isotropic state at 35 °C.
Production
5CB is produced by modifying biphenyl in a linear manner. First is added to the biphenyl to introduce a Bromine atom to the end of the moiety. Next aluminium chlorideAluminium chloride
Aluminium chloride is the main compound of aluminium and chlorine. It is white, but samples are often contaminated with iron trichloride, giving it a yellow colour. The solid has a low melting and boiling point. It is mainly produced and consumed in the production of aluminium metal, but large...
and
is added to the sample, followed by the addition of potassium hydroxidePotassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
and
. By this point the molecule will have a bromine atom on one end of the rigid core and on the other end. The introduction of copper(I) cyanideCopper(I) cyanide
Copper cyanide in an inorganic compound with the formula CuCN. This off-white solid occurs in two polymorphs; impure samples can be green due to the presence of Cu impurities. The compound is useful as a catalyst, in electroplating copper, and as a reagent in the preparation of...
and DMF results in the removal of the bromine and its replacement with CN. This is the final step in the production of 5CB.