2.6.5.3.4 s relatively quite rare as compared to other class of compounds discussed in this context. Example: Furfural.
A. Furfural
Chemical Structure 2-Furfuraldehyde (C5H4O2).
Occurrence It occurs in the first fraction of a number of essential oils, belonging to the natural order Pinaceae. It is also found in colophony (Pinus paulusteric); oil of orris rhizome (Iris florentina Linn., Family: Iridaceae); oil of lavender (Lavandula officinalis; family: Labiatae); oil of cinnamon
(Cinnamonium cassia Blums; Family: Lauraceae); and clove oil (Eugenia Caryophylus; Family: Myrtaceae).
Isolation It may be accomplished in two manners, namely:
(i) Extraction i.e., by washing the first fraction of the oil with water, extracting the aqueous layer with ether, and finally evaporating the ether under reduced pressure.
(ii) Addition Compound i.e., furfural forms an addition compound on being treated with a saturated aqueous solution of sodium bisulphite.
Characteristic Features It is a colourless oily liquid having a peculiar odour, somewhat resembling the odour of benzaldehyde. The physical characteristic features are: d204 1.1563; bp760 161.8°C; mp:– 36.5°C; volatile in steam; n20D 1.5261. It is soluble in ethanol and ether; soluble in 11 parts of water.
Identification
1. It gives an intense red colour with aniline acetate.
2. It is also identified by forming its corresponding oxime and phenyl hydrazone derivatives.
3. It reduces Fehling's solution to give red precipitate of cupric oxide.
4. It also reduces Tollen’s Reagent (i.e., ammoniacal silver nitrate solution) to give silver mirror.
Uses
1. It is used extensively in the manufacture of furfural-phenol plastics, for instance: Durite.
2. It is employed in solvent-refining of petroleum oils.
3. It makes its use as a solvent for nitrated cotton, gums and cellulose acetate.
4. It finds its application for accelerating vulcanization.
5. It is used as insecticide, germicide and fungicide.
6. It is employed in the manufacture of varnishes.
7. It is commonly used as a reagent in analytical chemistry.
