Reactions and characterisation of aliphatic amides

The student should carry out the following simple experiments with acetamide or with any other ahphatic amide, e.g., n-caproamide they illustrate some of the general reactions of primary ahphatic amides. 

Aliphatic amides may be hydrolysed by boiling with 10 per cent, sodium hydroxide solution to the corresponding acid (as the sodium salt) the alkahne solution should be acidified with dilute sulphuric acid any water-soluble acid may then be distilled from the solution. Alternatively, hydrolysis may be eflfected with 10-20 per cent, sulphuric acid. The resulting ahphatic acid (usually a liquid) may be characterised as detailed in Section 111,85. 

Crystalline derivatives may be prepared with xanthhydrol (9-hydroxy-xanthen), but the reagent is comparatively, expensive. Xanthhydrol reacts with primary amide,s with the formation of crystalline xanthyl-amides or 9-acylamidoxanthens  

Commercial xanthhydrol may be used, but the pure white product, m.p. 120-121°, obtained by the reduction of xanthone with sodium amalgam (Section VII,16) gives better results. 

Xanthylamides. Dissolve 0 25 g. of xanthhydrol in 3-5 ml. of glacial acetic acid if an oil separates (as is sometimes the case with commercial material), allow to settle for a short time and decant the supernatant solution. Add 0-25 g. of the amide, shake and allow to stand. If a crystalline derivative does not separate in about 10 minutes, warm on a water bath for a period not exceeding 30 minutes, and allow to cool. Filter oflF the solid xanthylamide (9-acylamidoxanthen) and recrystallise it from dioxan - water or from acetic acid - water, dry at 80° for 15 minutes and determine the m.p. 

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