[Chemistry Class Notes] Epoxide Pdf for Exam

A cyclic ether with a three-atom ring is known as an epoxide. This ring forms an equilateral triangle- a structure that makes it strained.

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An Overview of Epoxide

The three-atom ring of the epoxide is highly reactive. It is even stronger than the other ethers. Epoxide rings are produced on a large scale for many applications. With low molecular weight, these compounds exist as colorless, non-polar and volatile entities most of the time. The epoxides which find wide applications in the industry are ethylene oxide and propylene oxide. These are produced on a scale of 15 and 3 million tonnes per year, respectively.

What is The Basic Structure of Epoxide?

The basic structure of an epoxide consists of an oxygen atom which is attached to two adjacent carbon atoms that belong to a hydrocarbon. Further, a more complex form of epoxide is made up of epoxidation of alkenes. In this process, peroxy acid (RCO3H) is used in order to transfer an atom of oxygen. However, the general ethers can be regarded as the class of chemical compounds which contain an ether group. This group is the combination of oxygen, an atom that is connected to two alkyl or aryl groups. The formula for this is ROR in general terms which state that R and R represent the aryl or the alkyl groups. So, it can be concluded that the fundamental structure of it contains two carbons atoms of a hydrocarbon that is attached to an oxygen atom. 

An epoxide is regarded as the cyclic ether with a three-atom ring. Now, this ring which estimates an equilateral triangle makes it strained and therefore becomes highly reactive in comparison to the other form of ethers.  It is made up of the oxidation of ethylene over a silver catalyst. 

Applications of Epoxide

It is used as a fumigant and in order to make antifreeze, ethylene glycol and various other useful compounds. As we know, more complicated epoxides are generally made up by the epoxidation of alkenes. This takes place by the common usage of peroxy acid in order to transfer an atom of oxygen. 

Further, another common industrial method of getting epoxide involves a two-step process. In the first step, the alkene is converted into a chlorohydrin. In the second step, the chlorohydrin is treated with a base to eliminate hydrochloric acid which gives birth to the epoxide. This is the process to make propylene oxide. Further, it can be used for assembling polymers which are known as epoxies. These are an excellent form of adhesives and are also greatly helpful in surface coatings. One of the most common forms of epoxy resin is formed from the reaction of epichlorohydrin with a bisphenol-A.

How is Epoxide Synthesis?

Epoxide can be synthesized in numerous ways. Propylene oxide and ethylene oxide are the two different forms of epoxides that are made in a large amount with 15 to 3 tonnes each year. However, there are certain things to consider when talking about the oxidation of alkenes. So, when the alkenes are oxidized it is heterogeneously catalyzed. In this case, when ethylene reacts with oxygen under a silver catalyst, it leads to the formation of an epoxide. Now as per the stoichiometry, it can be expressed chemically as 

7H2C= CH2+6O2– 6C2H4O+ 2CO2+2H2O

What Happens When Epoxide is Homogeneously Catalysed for Asymmetric Epoxidation?

The chiral epoxides are produced from prochiral alkenes. Numerous metal complexes act as active catalysts. The most essential among them are vanadium, molybdenum and titanium. 

What is Nucleophilic Epoxidation?

By the usage of compounds such as peroxides, electron-deficient olefins can be epoxidized. Now, this form of reaction has two steps. In the first step, the nucleophilic conjugate is added to the oxygen atom in order to give a stabilized carbanion. However, in the case of biosynthesis, epoxides are not common in nature. They are made by oxygenation of alkenes. 

What Are The Uses of Epoxide?

The uses of epoxide are as follows:

• There are numerous uses of ethylene epoxide. This includes generation of surfactants and detergents.

• It is also used as a stabilizer in various forms of materials like PVC. Moreover, they are also used in the production of Epoxy resist that have low viscosity and which does not comprise strength and physical properties.

• Epoxides reaction with amines results in epoxy glues and structural materials. They are also useful in a few things for instance in aerosols, resins and also in chemical intermediates.

Why Are Certain Epoxides Toxic?

Majority of the epoxides are regarded as toxic. The reason for their toxicity is high reactivity that makes them mutagenic. The three-member epoxide rings are extremely strained. Thus, it is vulnerable towards ring-opening by nucleophiles. Some of the common nucleophiles are NH2, OH and S. Further there are many of such groups in biological systems. The reactions with OH and S are two of the mechanisms which the body uses in order to eradicate epoxides. However, there is negligible proof that epoxides can give birth to cancer but also again, unavoidable is the fact that the majority of the epoxides are mutagenic. They also form covalent bonds to guanine. Further, the adduct prevents the proper G-C base pairing. 

Brief Information on The Formation and Utilization of Epoxides

Epoxides are greatly helpful in functional groups with regards to organic chemistry in order to generate reactive centers. Majority of the drugs are harmful as well as beneficial. They rely on the process of epoxidation in order to become biologically active. There are two processes of epoxidation which are ring-closing and ring opening-reactions. Epoxides contain an oxirane that is a three-membered ring which contains an oxygen atom. To prepare epoxides a double bond is needed across which the oxygen is to be added across the C-C bond in order to form the oxirane ring. 

The ring-closing reactions can be accomplished in three different ways that start with an alkene reactant. MCPBA and Peroxy acids are commonly used peroxides that help in the preparation of an epoxide. Now, the third process needs hydroamination across the double bond in order to form a halohydrin. The intramolecular SN2 reaction gives birth to epoxide that forms due to the reaction with a strong base. Ring-opening and formation of alcohol via intermolecular SN2 reaction take place due to the reaction of epoxides with any strong nucleophile. Medical equipment sterilization by using ethylene oxide is one of the practical examples of ring-opening reactions where microbes present on the surface of the equipment are exposed to ethylene oxide.