FURFURANE, OR FURANE, AND ITS DERIVATIVES 303 



FURFURANE, OR FURANE, AND ITS DERIVATIVES. 



Furfurane and its derivatives contain a five-membered ring made up of 

 4 carbon atoms and i oxygen atom. 



The origin, main interest and importance of these compounds is in the 

 fact that they are formed from carbohydrates by dry distillation, or by distillation 

 with acids. The following compounds are so obtained : 



HC(/8) ()CH HC CH HC CH HC CH 



II ' II II II II II II II 



HC() ( a )CH HC C.CH 2 OH HC C . CHO CH 3 .C C . CHO 



o o o 



Furfurane Furfur- Furfur- o', or w-methyl- 



or alcohol. aldehyde, furfural. 



furane. furfural 



(furfurol). 

 HC CH HC CH 



HC C.COOH CH 2 OH C C . CHO 



V xx 



o o 



Pyromucic o', or aj-hydroxymethyl 



acid. furfural. 



Furfurane, C 4 H 4 O, is obtained by the distillation of the barium salt of 

 pyromucic acid and is contained in the tar from pinewood. Furfurane is a 

 liquid with a peculiar smell. It boils at 32 and is insoluble in water. It is 

 reduced to tetrahydrofurfurane when passed over zinc dust, or nickel dust, 

 heated to 170. It reacts violently with concentrated hydrochloric acid form- 

 ing a brown amorphous substance, and gives a purplish colour reaction with 

 sulphuric acid and isatin or phenanthraquinone. 



Furfuralcohol, C 4 H 3 O . CH 2 OH, is formed from furfuraldehyde by re- 

 duction, or by the action of caustic soda. It is present in the oil from roasted 

 coffee. It is a colourless liquid which boils at 171 and is easily soluble in 

 water. In solution it rapidly resinifies. It gives a blue-green colour to a 

 pinewood shaving moistened with hydrochloric acid. 



Furfuraldehyde, C 4 H 3 O . CHO. 



Furfuraldehyde or furfural is the chief compound of the group and is 

 formed from bran and other carbohydrates by distillation with dilute sulphuric 

 acid. It is formed quantitatively by the distillation of pentoses with dilute 

 acid and therefore serves in their estimation (p. 234) : 



O 



CH 2 OH CHOH.CHO HC C . CHO 



I =3H 2 0+ || || 



CHOH CHOH HC CH 



It is a colourless liquid, which boils at 162 and has a peculiar aromatic 

 smell. It turns brown in the air, is easily soluble in alcohol, but only slightly 

 soluble in water. 



It has all the properties of an aromatic aldehyde forming an oxime, a 

 hydrazone, etc. By alkali it is converted into a mixture of alcohol and alde- 

 hyde. It condenses with numerous other compounds. It gives colour re- 

 actions with a-naphthol and other phenols which serve in testing for 

 carbohydrates (p. 193). 



a-Methyl-furfuraldehyde, C 4 H 2 O . CH 3 . CHO, is formed by the 

 distillation of methyl pentoses with hydrochloric acid and resembles furfural. 



Hydroxymethyl-furfuraldehyde, C 4 H 2 O . CH 2 OH . CHO, is formed 

 in small quantities from hexoses, especially ketoses, by the action of concen- 

 trated acids. It resembles furfural. Molisch's reaction for carbohydrates 

 (p. 193) is due to this substance. 



Pyromucic Acid, C 4 H 3 O . COOH, is obtained by the dry distillation of 

 mucic acid or by the oxidation of furfural. It is a liquid which boils at 1 34. 



