52 Biological Chemistry. 



" branched-chain " formula) represents isobutane. There is a 

 simpler way of representing the formula which still indicates 

 the differences of structure in these compounds. Butane 

 may be represented by the formula CH 3 CH 2 CH 2 CH 3 , 

 or more simply still by the formula CH 3 (CH 2 ) 2 CH 3 , and 

 the " m> "-compound by the formula CH(CH 3 ) 3 . This 

 latter formula is taken to represent the fact that one 

 carbon atom is " united directly " to three other carbon, 

 atoms. It will be seen later that it is possible to deter- 

 mine experimentally the correct structural formula for 

 each of these compounds. 



The structural formulae representing paraffin hydro- 

 carbons with five carbon atoms of the empirical formula 

 C 5 H 12 (pentanes) are the following : 



(I.) (II.) (HI.) 



H H H H H 



| III H-C-H 



H C H H C C C-H H I H 



H-C H H H H-C - C - C-H 



I H-C-H | I | 



H-C H ) H H 



| H C-H H-C-H 



H-C-H | | 



| H H 



H C-H 



or or or 



CH 3 -CH 2 'CH 2 -CH 2 -CH 3 ^ 3 >CH CH 2 CH 3 C(CH 3 ) 4 



I. is called pentane, II. is called isopentane, and III. 

 tetramethyl methane, which may be considered as a 

 methane in which each hydrogen atom is replaced by 

 four CH 3 's (or what are called, as will be explained later, 

 methyl groups). 



It is quite easy to see from the above examples, that 

 the more complex it is, and the greater the number of 

 carbon atoms a substance contains, the greater is the pos- 



