IV] CHLOROPHYLL 33 



then contains in solution phytochlorin e, the derivative of chlorophyll a. The phyto- 

 chlorin e gives to the ether an olive-green colour. 



The ether layer remaining in the funnel, after the separation of the green-blue acid 

 layer, is now extracted with 10 c.c. of 12 o/q hydrochloric acid (sp. gr. 1-06 i.e. 38"1 c,c, 

 strong acid: 61*9 c.c. water). The green acid solution so obtained is diluted with 

 water and shaken with ether which then becomes coloured red and contains phyto- 

 rhodin ^, the derivative of chlorophyll h. 



If the phyllins are acted upon by mineral acids, they lose their 

 magnesium in the same way as the chlorophyllins, and the series of sub- 

 stances obtained in this way are termed porphyrins. Thus aetiophyllin 

 will give aetioporphyrin C31H36N4 (see Scheme 1, p. 35). 



The derivatives of chlorophyll which are free from magnesium, such 

 a.s phaeophytin, phytochlorin phytorhodin, the various porphyrins, etc. 

 combine readily with the acetates of some metals such as copper, zinc 

 and iron, and they form intensely coloured, stable compounds. The change 

 of colour is so noticeable that the smallest traces of certain metals can 

 be detected in this way. Hence it is very difficult to prepare the 

 magnesium-free chlorophyll unless the reagents are perfectly pure and 

 all contact with certain metals is avoided. 



Ex'pt. 26. Substitution of copper for magnesium in chlorophyll. 2 c.c. of an ether 

 solution of chlorophyll are shaken with a little 20% hydrochloric acid (sp. gr. 1-10 

 i.e. 62*4 c.c. strong acid : 37*6 c.c. water), and then washed with water in a separating 

 funnel. If the ether tends to evaporate and deposit phaeophytin in the funnel^ 

 a little more ether should be added. In this way is produced in ether solution the 

 magnesium-free chlorophyll derivative, phaeophytin. The solution is evaporated 

 down on a water-bath, and the residue dissolved in 5 c.c. of alcohol. The solution is. 

 olive-green in colour. This is heated and a grain of copper acetate or zinc acetate is- 

 added. The colour changes back to a brilliant green, but without fluorescence (if all 

 the chlorophyll has been converted into phaeophytin). 



From the results of these recent investigations, it is now possible to 

 write formulae for the two chlorophylls as follows: 



chlorophyll a (C32H30O N4Mg) (COOCH3) (COOC20H39) 

 chlorophyll h (C32H2802N4Mg) (COOCH3) (COOC20H39) 



from which it will be seen that the phytol component amounts to one- 

 third of the weight of the chlorophyll. The structural formula for 

 chlorophyll is not completely known, but there is evidence that it contains 

 four pyrrole rings (cp. the pyrrolidine alkaloids, p. 175). 



From the analyses of chlorophylls from different plants, it was found 

 that the phytol content varied, and plants which yielded little phytol 

 most readily produced "crystalline chlorophyll," a form of the pigment 

 which has been known for some considerable time to previous worker's^ 

 The Cow Parsnip (Heracleum Sphondylium), Hedge Woundwort {Stachys 



