Josh-Daniel S. Davis (joshdavis) wrote,
Josh-Daniel S. Davis

Ethylene (with Acetic acid to reduce unwanted isomerization)

Excerpt from RCM
An interesting application of Grubbs' Catalyst is in the aerospace industry. A spaceship's hull is a necessarily very strong material, but over time small microcracks in the structure can form. A new material used in the construction of spaceship hulls contains Grubbs' Catalyst, as well as capsules of dicyclopentadiene, which can undergo ROMP. When a crack in the hull forms, the capsules are ruptured and come into contact with Grubbs' Catalyst, which polymerizes dicyclopentadiene and seals the crack.

Excerpts from the Ethene page

The suffix -ene (a Greek root added to the end of female names meaning "daughter of") was widely used to refer to a molecule or part thereof that contained one fewer hydrogen atoms than the word being modified. Thus, ethylene (C2H4) was the "daughter of ethyl" (C2H5).

Chemist Augustus von Hofmann proposed a system of hydrocarbon nomenclature in which the suffixes -ane, -ene, -ine, -one, and -une were used to denote the hydrocarbons with 0, 2, 4, 6, and 8 fewer hydrogens than their parent alkane[1]. In this system, ethylene became ethene.

The double bond is a region of slightly higher electron density, and most of ethylene's chemistry involves other molecules reacting with and adding across its double bond. Ethylene can react with bromine, chlorine, and other halogens, to produce halogenated hydrocarbons. It can also react with water to produce ethanol, but the rate at which this happens is very slow unless a suitable catalyst, such as phosphoric or sulfuric acid, is used. Under high pressure, and, in the presence of a catalytic metal (platinum, rhodium, nickel), hydrogen will react with ethylene.

Ethylene is produced in the petrochemical industry via steam cracking. In this process, gaseous or light liquid hydrocarbons are briefly heated to 750–950 °C, causing numerous free radical reactions to take place. Generally, in the course of these reactions, large hydrocarbons break down in to smaller ones and saturated hydrocarbons become unsaturated.

The result of this process is a complex mixture of hydrocarbons in which ethylene is one of the principal components. The mixture is separated by repeated compression and distillation.

Another process is catalytic cracking where it is used in oil refineries to crack large hydrocarbon molecules into smaller ones. Use of zeolite as a catalyst allows the cracking to be achieved at a lower temperature. It is an important way of separating alkenes from alkanes using a fractionating column.

Ethylene is used primarily as an intermediate in the manufacture of other chemicals, especially plastics. Ethylene may be polymerized directly to produce polyethylene (also called polyethene or polythene), the world's most widely-used plastic. Ethylene can be chlorinated to produce ethylene dichloride (1,2-Dichloroethane), a precursor to the plastic polyvinyl chloride, or combined with benzene to produce ethylbenzene, which is used in the manufacture of polystyrene, another important plastic.

Smaller amounts of ethylene are oxidized to produce chemicals including ethylene oxide, ethanol, and polyvinyl acetate.

Ethylene was once used as an inhaled anesthetic, but it has long since been replaced in this role by nonflammable gases.

It has also been hypothesized that ethylene was the catalyst for utterances of the oracle at Delphi in ancient Greece.

Ethylene functions as a hormone in plants. It stimulates the ripening of fruit, the opening of flowers, and the abscission (or shedding) of leaves. Its biosynthesis starts from methionine with 1-aminocyclopropane-1-carboxylic acid (ACC) as a key intermediate.

"Ethylene has been used in practice since the ancient Egyptians, who would gas figs in order to stimulate ripening. The ancient Chinese would burn incense in closed rooms to enhance the ripening of pears. It was in 1864, that leaks of gas from street lights showed stunting of growth, twisting of plants, and abnormal thickening of stems (the triple response)[see plant senescence](Arteca, 1996; Salisbury and Ross, 1992). In 1901, a russian scientist named Dimitry Neljubow showed that the active component was ethylene (Neljubow, 1901). Doubt discovered that ethylene stimulated abscission in 1917 (Doubt, 1917). It wasn't until 1934 that Gane reported that plants synthesize ethylene (Gane, 1934). In 1935, Crocker proposed that ethylene was the plant hormone responsible for fruit ripening as well as inhibition of vegetative tissues (Crocker, 1935). Ethylene is now known to have many other functions as well."

Inhibiting effects of ethylene on shoot growth (more specifically on stem elongation) reduced in the presence of light. Also ethylene levels are decreased by light

The above may be because light induces auxin synthesis and moderate auxin levels inhibit ethylene.
Tags: chemistry
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