ORGANIC MEDICINAL CHEMICALS 35 



CONDENSED RING COMPOUNDS 



15. Naphthalene and its Derivatives. 



1 6. Anthracene and its Derivatives. 



17. Phenanthrene and its Derivatives. 



1 8. Pyridine Group. 



19. Chinoline Group. 



20. Alkaloids of Complicated Composition. 



21. Hydrated Benzenes (Terpenes and Camphors). 



22. Tars and Glucosides. 



23. Albumins and Albuminoids. 



The organic compounds of the various classes may be briefly defined 

 as follows: 



CLASS I. METHANE OR FATTY ACID SERIES 



1. HYDROCARBONS of this series are the compounds of carbon and hydro- 



gen, having the carbon atoms connected in a chain thus, 

 methane, CH 4 ; ethane, CH 3 -CH 3 ; propane, CH 3 -CH 3 -CH 2 . 



These compounds are the first of a series of compounds 

 varying by the increment CHa. They may be taken as illus- 

 trative of many such series of organic compounds, called 

 homologous series. 



When there are four or more atoms of carbon in the mole- 

 cule, the carbon atoms may form branching chains, as in 

 isobutane. 



This compound has the same percentage composition, but 

 has different properties from butane, CHg-CHz-CHz-CHs. 

 This is called isomerism. 



Unsaturated hydrocarbons or derivatives have atoms of 

 carbon united to one another by two or three bonds of affinity 

 thus, ethylene, CH 2 = CH 2 ; acetylene, CH = CH. These 

 compounds will unite with halogens or halogen acids without 

 an equivalent loss of hydrogen. 



2. HALOGEN SUBSTITUTION PRODUCTS are hydrocarbons in which one or 



more atoms of hydrogen are replaced by a corresponding number 

 of atoms of a halogen thus, chloroform, CHC1 3 ; iodoform, CEQ 3 . 



3. ALCOHOLS are formed by the replacement of one or more hydrogen 



atoms of a hydrocarbon by a corresponding number of hydroxyl 

 (OH) groups. They are of neutral reaction, but analogous to 

 metallic hydroxides. They combine with acids, losing water, 

 forming compounds analogous to salts, termed esters. They 

 may also be defined as hydroxyl combined with an alkyl radical* 

 thus, alcohol (ethyl hydroxide), C 2 H 5 OH. 



* Radicals. It is usual to designate as radicals those groups of atoms which are found repeating 

 themselves in a comparatively large number of compounds derived from one another, and in which 

 these combinations play the part of simple elements: e.g., CHa is called the methyl radical, CHs-Cl 

 is methyl chloride, CHsOH is methyl alcohol, etc. CHj-CO- is termed the acetyl radical and 

 CiHO-Cl is acetyl chloride, etc. ; 



