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Alcohol

Reactions

The plastics industry is a major consumer of all types of alcohols, because they are intermediates in a large variety of polymer syntheses. The hydroxyl group is the part of an alcohol that makes the molecule relatively reactive and thus very useful in synthesis. Dozens of reactions are possible. Important esters made from ethanol include the insecticide malathion, the fragrance compound ethyl cinnamate, and the polymer building blocks ethyl acrylate and ethyl methacrylate. Examples of esters made from methanol include methyl salicylate (oil of wintergreen), the perfume ingredients methyl paraben and methyl benzoate, and the polymer starting material methyl acrylate. High-molecule-weight alcohols converted into esters are widely used as plasticizers in the polymer industry, and very high-molecule-weight alcohols with 12-18 carbon atoms are used to make biodegradable surfactants (detergents).

Alcohols can also be oxidized. If the alcohol's hydroxyl group is at the end of a carbon atom chain, an oxidation reaction produces either a carboxylic acid or an aldehyde. If the hydroxyl group is attached in the middle of a straight carbon atom chain, an oxidation reaction produces a ketone. An alcohol whose hydroxyl group is attached to a carbon atom that also has three other carbon branches attached to it cannot be oxidized.

The formation of double bonds in hydrocarbons can be accomplished by the dehydration of alcohols. Acid added to the alcohol removes not only the hydroxyl group, but also a hydrogen atom from an adjacent carbon atom. The reaction is called a dehydration, because H-OH (water) is removed from the molecule and a double bond forms between the two carbon atoms.


Resources

Books

Bailey, James E. Ullmann's Encyclopedia of Industrial Chemistry. New York: VCH, 2003.

Bruice. Paula. Organic Chemistry. 3rd ed. Englewood Cliffs, NJ: Prentice-Hall, 2001.

Meyers, Robert A. Encyclopedia of Analytical Chemistry: Applications, Theory and Instrumentation. New York: John Wiley & Sons, 2000.

Szmant, H. H. Organic Building Blocks of the Chemical Industry. New York: Wiley, 1989.


Gail B. C. Marsella

KEY TERMS


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Alcohol

—Any of the large number of molecules containing a hydroxyl (OH) group bonded to a carbon atom to which only other carbon atoms or hydrogen atoms are bonded.

Azeotrope

—A mixture of certain substances that distill together at the same boiling temperature, instead of separately.

Destructive distillation

—An antiquated process for obtaining small amounts of alcohols, particularly methanol, from wood. The wood is heated to a high temperature in the absence of air, and gradually decomposes into a large number of chemicals.

Distillation

—Collecting and condensing the vapor from a boiling solution. Each distinct, volatile chemical compound boils off individually at a specific temperature, so distillation is a way of purifying the volatile compounds in a mixture.

Ester

—A molecule with a carbon both bonded to an ether linkage (carbon-oxygen-carbon), and double bonded to an oxygen.

Fermentation

—The action of yeast metabolism on sugar solutions, resulting in the production of ethanol and carbon dioxide.

Glycol

—An alcohol with two hydroxyl groups bonded to adjacent carbons in the molecule. Also called a diol.

Grignard synthesis

—A classic laboratory method of preparing alcohols. An alkyl halide is first reacted with magnesium, and then the addition of an aldehyde or ketone results in the formation of the alcohol.

Hydroxyl group

—The -OH group attached to a carbon atom in a molecule. If the carbon atom itself is attached to only other carbon atoms or hydrogen atoms, the molecule is an alcohol.

Intermediate

—In a chemical synthesis, any compound that is generated only to be used in the next step of the process.

Polyol

—An alcohol with many hydroxyl groups bonded to the carbon atom backbone of the molecule.

Primary alcohol

—An alcohol with the hydroxyl group at one end of the chain of carbon atoms.

Secondary alcohol

—An alcohol with the hydroxyl group in the middle of a straight chain of carbon atoms.

Synthesis gas

—A mixture of carbon monoxide and hydrogen gases, obtainable both from coal and natural gas, and used widely for the synthesis of alcohols and other organic compounds in the chemical industry.

Tertiary alcohol

—An alcohol with the hydroxyl group in the middle of a branched chain of carbon atoms.

Additional topics

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