266 BOGERT— CARBON COMPOUNDS. [April 20. 



extended until the former covered all acyclic compounds and the 

 latter nearly all cyclic. This subdivision of organic chemistry has 

 -been generally adopted (with few exceptions) ever since. More 

 recently, it has been found advisable, particularly in the larger text- 

 books, to split up aromatic chemistry into carbocyclic and hetero- 

 cyclic. So that we now have the three classes, fatty (or aliphatic), 

 carbocyclic (or isocarbocyclic), and heterocyclic. And yet this clas- 

 sification is no longer satisfactory, for there is no sharp dividing 

 line between straight-chain and cyclic compounds, the one merging 

 gradually into the other. Certain cyclic structures (as the ethylene 

 oxides, lactones, lactames, imides, etc.) are invariably discussed 

 under fatty chemistry, and certain straight-chain compounds (like 

 the olefin terpenes and their derivatives) are generally taken up 

 under aromatic chemistry, while the alicyclic compounds, as their 

 name indicates, form the natural transition from aliphatic to cyclic 

 structures. 



With the filling in of the gaps heretofore existing between ali- 

 phatic and aromatic chemistry, the time seems appropriate for a 

 change in our classification of carbon compounds which shall recog- 

 nize the essential unity of the subject, and no longer give the im- 

 pression that organic chemistry is composed of three varieties of 

 chemistry — fatty, carbocyclic and heterocyclic. 



The method which appeals particularly to the writer, and which 

 he has followed with his classes at Columbia University for the 

 past ten years, is to begin with the hydrocarbons, as the simplest 

 carbon compounds, and discuss in succession the various series of 

 hydrocarbons, saturated and unsaturated, acyclic and cyclic, before 

 passing on to the next group. After a careful consideration of 

 these fundamentally important compounds, other classes of carbon 

 compounds are taken up in similar manner ; all of the simple halogen 

 derivatives being considered together, all the nitro bodies, all the 

 alcohols, and so on. All other classes are very conveniently regarded 

 as derivatives of the hydrocarbons. With a knowledge of the prop- 

 erties of the various series of hydrocarbons, the study of their 

 derivatives then resolves itself chiefly into the following questions: 

 (i) What are the characteristic properties of the group under con- 



