CHAPTER VI 



THE PHENYL METHANE DYES 



ONE of the most important groups of dyes, both from the stand- 

 point of the dyer and from that of the biologist, is a group of 

 substituted methanes, or in other words compounds with a 

 central carbon atom. In methane, CH4, it is possible to replace 

 any of the hydrogen atoms with methyl, ethyl, or phenyl groups. 

 If one H is replaced with CH3, it becomes ethane, CHs-CHs- 

 If two are replaced with CH3 groups it becomes propane, 

 'CH3CH2CH3; while if there are three substituent CH3 groups 

 it becomes iso-butane: 



CH, CH, 



\ / 

 C 



/ \ 

 CH3 H 



Similarly if one H is replaced with a phenyl group it becomes 

 phenyl methane or toluene: 



_CH3 



if with two it becomes di-phenyl methane 



if with three it becomes tri-phenyl methane; 



Certain substitution products of the di- and tri-phenyl methanes 

 are among the most powerful dyes known. 



Di- and tri-phenyl methane, themselves, are not dyes, nor are 

 they chromogens. They lack both the chromophore and the auxo- 

 chrome groups. The first step (theoretically) in converting them 

 into dyes is to introduce an -OH group in the place of one of the 

 unsubstituted H atoms of the methane nucleus. The compound 

 thus formed, which bears the same relation to the phenyl methane 



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