ORGANIC CHEMISTRY 373 



formaldehyde. Chlorophyll is apparently such a substance ; but 

 they have not, as yet, reported any experiments with this 

 compound, as they wished in the first instance to investigate 

 the simplest case. They point out that the use of chlorophyll 

 as a photo-catalyst introduces the possibility of synthesis of 

 optically active sugars, and the results of their investigations 

 of the action of this compound should be of the greatest interest. 



The mechanism of the action of the photo-catalyst is ex- 

 plained on the theory recently propounded by Baly and 

 Barker {Trans. Chem. Soc, 1921, 119, 653), which is dealt with 

 in Recent Advances in Physical Chemistry in the October 

 number of this Review. This explanation seems to be sup- 

 ported by the work of Ursprung {Ber. Dent. Bot. Ges., 191 8, 36, 

 6) on the relation between absorption in the infra-red and 

 visible spectrum and starch formation in the green leaf. 



A Cyclic Iodine Compound. — ^A paper by Collie and Reilly 

 {Trans. Chem. Soc, 1921, 119, 1550) describes a new type of 

 organic compound containing iodine, obtained from the barium 

 salt of diacetylacetone. When this compound is treated in 

 alcoholic suspension with iodine a new barium salt is obtained 

 which, when treated with dilute acids, gives a compound of the 

 formula C^H^OjI, which possesses rather unusual properties. 

 Two atoms of iodine react for each atom of barium, only one 

 half, however, appearing as barium iodide. The differential 

 action of the iodine on the barium suggests that the barium 

 salt of diacetylacetone must contain at least two barium atoms 

 in the molecule, and that these must be attached in a different 

 manner. The ordinary formula for diacetylacetone, CH, • 

 CO • CH2 • CO • CH2 • CO • CH„ does not provide for the formation 

 of such a barium salt, and it is suggested that this compound 

 has a cyclic structure. 



^C(CH,) • CH^ 

 HO -Of ^ '^ >C-OH 



X(CH3) : CH^ 



The barium salt of such a compound would contain the metal 

 attached in two ways, namely, replacing the hydrogen atom 

 of a hydroxyl group attached in one case to oxygen, and in the 

 other to carbon. 



Even on such an assumption it is difficult to explain the 

 formation of the compound C,H,03l from the barium salt of 

 diacetylacetone. The action of iodine is not analogous to the 

 case of the sodium salt of acetyl acetone which gives tetra- 



acetylethane, 



CHa-CO-CH-CO-CHs 



2CH8-CO-CHNa-CO-CH3 -> | 



CH3 • CO • CH • CO • CH3, 



