644- 



APPENDICES 



Ethers- — These are formed by the union of two alcohol molecules, 

 with dehydration. 



CHg . CHo 



CH., . CH., 



H 

 OH 



CHg . CHo 

 CHg . CHo 







Esters. — These are formed by linking an alcohol and an acid mole- 

 cule with dehydration. 



CHg . CHo OH 



CH., .CO OH 



CHa . CH. 

 CH., . Co" 



Anhydrides. — These are formed by the union of two acid molecules 

 with dehydration. 



CHo. . CO 



OH 



CH.. . CO . OiH 



CH, . CO 



CH., . CO 



^0 



Cyclic Compounds. 

 (1) An important series of carbon compounds contains a ring of six 

 carbons, each with an unsatisfied affinity, thus : — 



I 

 C 



^\ 



-C c- 

 — c c— 



\/ 

 c 



When each hand holds a hydrogen, Benzene is formed. 



These hydrogens may be replaced by various molecules giving rise to 

 a large series of different compounds. 



(2) If a ring contains atoms of other elements besides carbon, it is called 

 heterocyclic. One of the most important of these is Pyrrol — 



H— C— C— H 



II II 

 H— C C— H 



N 



I 

 H 



which occurs, linked to a benzene ring, in certain important constituents 

 of the protein molecule. 



