An Introduction to Functional Groups in Organic Chemistry：在有机化学官能团的引入.doc

An Introduction to Functional Groups in Organic Molecules Portions of this experiment were adapted from Lehman, J. W., Operational Organic Chemistry, Upper Saddle River, New Jersey: Prentice-Hall, 1999. Introduction Qualitative organic analysis, the identification of organic compounds based on their physical and chemical properties, is analogous in some ways to the identification of plants and animals according to their taxonomy—their structural features and presumed natural relationships. To classify an organic compound into a given family requires first detecting a specific functional group (characteristic set of atoms) in the molecules of organic compounds. Because functional groups influence the physical, chemical, and spectral properties of an organic compound, a chemist can identify a compounds functional groups by measuring certain physical properties, observing its chemical behavior with different classification reagents, and studying other spectral data. In this experiment we will subject a series of organic compounds to specific chemical reactions in order to identify which class of functional group the substance belongs to. Some common organic functional groups Functional group name General formula* Alkene Alkyl halide Alcohol Aldehyde (R–CHO) Amide Amine Carboxylic acid Ester Ether Ketone Functional group identification tests Chemists have developed a number of simple chemical tests that are positive only for compounds having certain kinds of functional groups. These are the four tests we will be performing today: Compounds that are easily oxidized react with a solution of chromium(VI) oxide in sulfuric acid, commonly referred to as chromic acid. Primary and secondary alcohols react within 2-3 seconds to form an opaque blue-green suspension. Aldehydes give the same result but usually take 10 seconds or more to react. Aldehydes and ketones both react with 2,4-dinitrophenylhydrazine (DNPH) reagent to yield yellow or orange precipi