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Ethyl Group

atoms carbon ethane atom

Ethyl group is the name given to the portion of an organic molecule that is derived from ethane by removal of a hydrogen atom (-CH2CH3). An ethyl group can be abbreviated in chemical structures as -Et. The ethyl group is one of the alkyl groups defined by dropping the -ane ending from the parent compound and replacing it with -yl. By this terminology, the ethyl group is derived from the parent alkane, ethane. Ethane has the molecular formula of CH3CH3. It is composed of two carbon atoms connected by a single bond, (C-C) and in turn, each carbon atom has three single bonds to hydrogen atoms (C-H). The ethyl group is the two carbon atom unit that is connected to a longer chain of carbon atoms or possibly a benzene ring.

Ethane is a gas at room temperature and burns very easily. The word ethane is derived from aithein, the Greek word for to blaze or to kindle. Ethane makes up about 15% of natural gas and can also be isolated from crude oil. It is used by industries for the production of ethylene and ethyl chloride.

Ethylene has the chemical formula of H2C=CH2 and is composed of two carbon atoms connected by a double bond (C=C), each carbon atom is also bonded to two hydrogen atoms (C-H). Ethylene is made by heating a mixture of steam and ethane to very high temperature. Ethylene is used in the manufacture of the polymer, polyethylene, which as the name implies, consists of many two carbon atom units linked into a long chain. Polyethylene is the clear wrap that is used in grocery stores and homes for wrapping and preserving food. Polyethylene can also be colored and coated onto wires for insulation. Ethylene is converted into ethylene oxide by the addition of an oxygen atom with oxygen gas. Ethylene oxide is mixed with gaseous chlorofluorocarbons to make a gas blend used to sterilize medical equipment and materials that are sent into outer space.

When ethane and chlorine are heated to high temperatures, they undergo a chemical reaction that results in the product, ethyl chloride (CH3CH2Cl). Ethyl chloride is an alkyl halide that has of one of the hydrogen atoms of ethane replaced by a chlorine atom. Ethyl chloride is commonly used as a substrate for the addition of an ethyl group on to a benzene ring or another organic chemical. For example, two ethyl chloride molecules are used to make an important ingredient in sleeping pills called barbital or 5,5-diethylbarbituric acid. When ethyl chloride is rubbed onto the skin, it causes the skin to become numb or to loose all feeling. This local anesthetic property of ethyl chloride is used by members of the medical community to stop pain when lancing of boils and giving injections.

The incorporation of an ethyl group or chain of two carbon atoms into a molecule's structure can change the properties of the compound drastically. Butanoic acid is an acid composed of four carbon atoms. It is easily identified by its odor of rancid butter. When butanoic acid is converted into its ethyl ester, ethyl butyrate, it loses its disgusting smell. Ethyl butyrate has a broad spectrum of commercial applications from the perfume industry where it is routinely used for its rose fragrance to the food industry where its addition results in a natural pineapple flavor. Benzoic acid, another organic acid, is used as a food preservative because it does not interfere with the other flavors present. The corresponding ethyl ester of benzoic acid is ethyl benzoate. It is used as one of the primary ingredients of many kinds of fruit and berry flavored chewing gum. In the pharmaceutical industry, the addition of an ethyl group to a drug can have a profound effect on its properties. Barbital, or 5,5-diethylbarbituric acid, is used as a sedative and is a common component of many sleeping pills, whereas barbituric acid, the compound without the ethyl groups, has no calming or sleep inducing properties at all.

Resources

Books

Arctander, S. Perfume and Flavor Materials of Natural Origin. Elizabeth, NJ: S. Arctander, 1960.

Carey, Francis A. Organic Chemistry. New York: McGraw-Hill, 2002.

Kirk-Othmer. Encyclopedia of Chemical Technology. New York: Wiley, 1991.

KEY TERMS

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Ethane

—The molecule whose formula is CH3CH3 and is composed of two carbon atoms connected by a single bond, (C-C) and each carbon atom has three single bonds to hydrogen atoms (C-H).

Ethyl chloride

—The molecule whose chemical formula is CH3CH2Cl and is an alkyl halide that has of one of the hydrogen atoms of ethane replaced by a chlorine atom.

Ethyl group

—The portion of an organic molecule that is derived from ethane by removal of a hydrogen atom (-CH2CH3).

Ethylene

—The molecule whose chemical formula is H2C=CH2 and is composed of two carbon atoms connected by a double bond (C=C), each carbon atom is also bonded to two hydrogen atoms (C-H).

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