Ester An organic compound that contains

Lactone An organic compound that contains an ester group incorporated into a carbon ring structure. Lactones include the coumarins, e.g. umbelliferone or 7-hydroxycoumarin. Lactones and furocoumarins, e.g. bergaptene, exist in small quantities in essential oils and should be used with care. Lactones can be neurotoxic (poisonous to the nervous system) and cause skin allergies. Bergaptene is well known for its phototoxicity on the skin. 

Infrared (IR) spectroscopy is probably the quickest and cheapest of the spectroscopic techniques in determining the functional groups of the sample. The samples can be soUds, liquids, or gases and can be measured in solution or as neat liquids mulled with KBr or mineral oil. Comparison of IR spectra of substances of known structure has led to many correlations between wavelength (or frequency) of IR absorption and features of molecular structure. Certain structural features can easily be established. For example, in an organic compound that contains only C, H and O, the oxygen can only be present as C=0,0—H, or C—O—C or a combination of these, such as the ester or carboxylic acid group. 

A carbonyl group has a carbon atom and an oxygen atom connected with a double bond (i.e., C=0). Four kinds of organic compounds that contain only C, H, and O have a carbonyl group aldehydes, ketones, carboxylic acids, esters. 

A second reason for the vast number of organic compounds is that carbon atoms can form stable bonds with other elements. Several families of organic compounds (alcohols, aldehydes, ketones, esters, and ethers) contain oxygen atoms bonded to carbon. Others contain nitrogen, sulfur, or halogens. The presence of these elements confers a wide variety of new chemical and physical properties on an organic compound. 

Although the two isomers contain exactly the same atoms, their different arrangements of atoms result in two very different compounds. The first is an aldehyde called propanal. The second is a ketone called acetone. Aldehydes and ketones are two classes of organic compounds. The classes of organic compounds that we will discuss in this chapter are alcohols, carboxylic acids, aldehydes, ketones, esters, amines, and amides. 

Dibasic Acid Esters. Dibasic acid esters (diesters) are prepared by the reaction of a dibasic acid with an alcohol that contains one reactive hydroxyl group (see Esters, organic). The backbone of the stmcture is formed by the acid. The alcohol radicals are joined to the ends of the acid. The physical properties of the final product can be varied by using different alcohols or acids. Compounds that are typically used are adipic, azelaic, and sebacic acids and 2-ethyIhexyl, 3,5,5-trimethyIhexyl, isodecyl, and tridecyl alcohols. 

The only accident that involves a saturated ester is the result of an attempt to extract an organic residue containing hydrogen peroxide with ethyl acetate. The latter was mixed with methanol and refluxed with the residue and hydrogen peroxide in an aqueous solution. A second extraction was carried out with acetate and the liquid was then evaporated. The small quantity of the compound that remained after the evaporation detonated violently. It was thought that this detonation was the result of the violent decomposition of methyl hydroperoxide, peracetic acid and/or ethyl peracetate. 

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