ABSTRACT
Classical Methods The determ ination of the structure of a naturally occurring organic com pound is an im portant milestone in its chemical history. Over the years, various m ethods and techniques, w ith procedural variations, have been developed for this purpose. Some of these are of a general nature and some others are specifically designed for a particu lar type of com pound. In the early days of classical organic chemistry, a well-defined sequence of steps was used in structural studies. After determ ining the m olecular form ula of a pure com pound, it was custom ary to subject it to various analytical and degradation procedures. Detection of functional groups is the prim ary step. The presence of basic or acidic functionalities is readily revealed by solubility tests. For example, the presence of a carboxylic acid group is shown by the com pounds solubility in aqueous sodium bicarbonate. This could be confirm ed by esterification; ethereal diazom ethane is a convenient reagent for the preparation of m ethyl esters. O n the other hand, a basic com pound, such as an amine, dissolves in aqueous hydrochloric acid. For the detection of other functional groups like the hydroxyl and carbonyl (aldehydic or ketonic), derivatisation is used (acetylation for the hydroxyl and form ation of an oxime or 2 , 4-dinitrophenyl hydrazone derivative for the carbonyl group).
