54 Suggestions fo Teachers of Biochemisfry [Sept. 



terol have shown its resemblance to fats and lecithins in the matter of 

 solubilities, but have indicated its difference from both fats and lecithins 

 in the matter of saponification. Like fats, but unhke lecithins, choles- 

 terols consist solely of carbon, hydrogen and oxygen. The available 

 data for the percentage elementary composition of most cholesterols 

 indicate that the general molecular nature of the crystalline form of the 

 most common member of the cholesterol group is correctly represented 

 by the following empirical formula for that substance (with water of 

 crystallization) : CotH^^OjHsO. The essential facts in our knowledge 

 of the chemical Constitution of cholesterols are that these substances 

 (a) are mono-hydroxy alcohols, that (ö) each of their molecules con- 

 tains at least one double bond (unsaturated), and that (c) the mole- 

 cules are largely terpene-like in structure. The appended constitutional 

 iormulas have been proposed: 



L^ 



HO— CH. /CH HO— CH. y;CH 



I XbHssCII I X3H3/ 



CH/ \CH CH/ \CHj 



proposed constitutional formulas for typical cholesterol, C27H44O. 



"471. Terpenes occur in many plants, where they appear to be 

 waste products. Terpenes are hydrocarbons with compositions indi- 

 cated by the following general formula: (CgHs)«. Each of the mole- 

 cules of nearly all the terpenes contains at least one ' carbon ring.' One 

 of the familiär oxy-derivatives of terpenes is camphor, CioH^gO. 

 Terpenes may be regarded as complex benzene derivatives, since cam- 

 phors and also various terpenes of the type represented by the formula 

 (C5H8)2 can readily be converted into cymene, {C^Yi-j)^, which is 

 /»-isopropyl-methyl benzene, CH3 — CgH^ — C3H7. 



" Each of the above constitutional formulas may be written in more 

 Condensed form, to show strikingly the terpene relationships of choles- 

 terols, as f ollows : 



HO— CH . 



CH/ 



"472. When an alcoholic Solution of cholesterol is treated with 

 J-methyl furol and concentrated sulfuric acid Solution, a pink color 

 is produced and the resultant liquid exhibits characteristic spectral 

 absorption bands. This reaction is very significant in its bearing on 

 the chemical relationships of cholesterols, for it is given also (a) by 

 various derivatives of camphor; {b) hy abietic acid, CigHgjCOOH, one 



