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Glossary Absolute configuration The arrangement of substituents about a stereoisomer, labeled R or S according to sequence rules. Abstraction The removal of an atom. Acene A linear arrangement of fused benzenes, such as the three-ring system anthracene. Acetal R₂C(OR')₂, the stable product of acid-catalyzed addition of excess alcohol to an aldehyde or ketone. Acetaldehyde CH₃CHO, the aldehyde corresponding to acetic acid. Acetal hydrolysis Conversion of an acetal into a carbonyl compound and an alcohol in the presence of catalytic acid and excess water. Acetic acid CH₃COOH, the carboxylic acid familiar as a dilute aqueous solution-vinegar. Acetoacetic acid synthesis Synthesis of a 3,3-disubstituted methyl ketone by alkylation of a ß-ketoester. Acetone The common name of 2-propanone (dimethyl ketone), Acetyl group The group Acetylene The common name of ethyne, HC=CH. Achiral molecule A molecule with reflection symmetry, and so superimposable on its mirror image. Acid dissociation constant A mathematical measure of acid strength, determined from the equilib- rium constant in reaction with water. Activating group Substituents speeding up a reaction, like electron-donating groups on benzene under electrophilic attack. Acyl anion equivalent A reagent bearing a negatively charged carbon atom that can be converted into a carbonyl group. Acyl group RCO-, as in the acyl halides, carboxylic acid derivatives. Acylium cation an intermediate in Friedel-Crafts alkanoylation. Adams's catalyst PtO₂, a catalyst that converts into colloidal platinum in the presence of hydrogen. Addition A reaction in which a bond is broken and new single bonds form. Nucleophilic substitution with a carboxylic acid or acid derivative by means of a tetrahedral intermediate. Adenine (A) One of the four bases in both DNA and a polyfunctional bicyclic nitrogen heterocycle. Alcohol An organic molecule whose functional group is the hydroxy group, -OH. Aldaric acid A dicarboxylic acid, also called saccharic acid, formed by vigorous oxidation of sugars with nitric acid. Aldehyde An organic molecule in which the carbonyl group, C=0, is bound to one hydrogen and one car- bon atom. Alditol A polyhydroxy compound produced by sugar reduction. Aldol condensation Conversion of aldehydes to α, aldehydes through an enolate by cat- alytic base and heating. Aldonic acids Carboxylic acid products of Fehling's and Tollen's tests or bromine oxidation on sugars. Aldose A sugar based on aldehydes-so that a three-carbon chain would be an aldotriose, for example. Aliphatic compound A nonaromatic compound. Alkaloid A physiologically active polycyclic compound containing nitrogen, often in a heterocycle-such as cocaine. Alkanal The systematic name for an aldehyde, such as methanal for formaldehyde. Alkanamine The Chemical Abstracts name for an aliphatic amine, such as methanamine (methylamine, aminomethane). Alkane A hydrocarbon containing only single and so an organic molecule lacking a functional group. 503