DECOMPOSITION OF ORGANIC COMPOUNDS. 453 



a. The atoms may arrange themselves differently within the mole- 

 cule. Ammonium cyanate, NH 4 CNO, is easily converted into urea, 

 CO(NH 2 ) 2 . This is called molecular rearrangement. 



b. A molecule may split up into two or more molecules. For 

 instance : 



C 6 H 12 6 : : 2C 2 H 6 O + 2CO 2 . 

 Grape-sugar. Alcohol. Carbon dioxide. 



This decomposition is spoken of as cleavage. When cleavage is 

 accompanied by the taking up of the constituents of water the change 

 is called hydrolytic cleavage or hydrolysis. The following reaction 

 belongs to this class : 



C 9 H 9 NO 3 + H 2 O = C 7 H60 2 + C 2 H 3 NH 2 O 2 . 



Hippur'ic acid. Benzoic acid. Glycocoll. 



c. Two molecules, either of the same kind, or of different sub- 

 stances, may unite directly : 



C 2 H 4 -f 2Br = C 2 H 4 Br 2 . 

 Ethylene. Bromine. Ethylene bromide. 



d. Atoms may be removed from a compound without replacing 

 them by other atoms : 



C 2 H 6 + O = C 2 H 4 O + H 2 O. 

 Alcohol. Oxygen. Aldehyde. Water. 



e. Atoms may be removed and replaced by others at the same 

 time (substitution) : 



C 2 H 4 O 2 + 2C1 = C 2 H 3 C1O 2 + HC1. 



Acetic acid. Chlorine. Monochloracetic Hydrochloric 

 acid. acid. 



Action of heat upon organic substances. As a general rule, 

 organic bodies are distinguished by the facility with which they 

 decompose under the influence of heat or chemical agents ; the more 

 complex the body is, the more easily does it undergo decomposition 

 or transformation. 



Heat acts differently upon organic substances, some of which may 

 be volatilized without decomposition, while others are decomposed 

 by heat with generation of volatile products. This process of heating 

 non-volatile organic substances in such a manner that the oxygen of 

 the atmospheric air has no access, and to such an extent that decom- 

 position takes place, is called dry or destructive distillation. 



The nature of the products formed during this process varies not 

 only with the nature of the substance heated, but also with the tem- 

 perature applied during the operation. The products formed by 

 destructive distillation are invariably less complex in composition, 



