_ INSECT POWDER 75 
This acid was converted into the chlorid and combined with 
pyrethrolon to form pyrethrin II, which is represented by the formula 
CH3 
| 
CH 
PE EGAN 
H.C CHCH,CH=C=CH(CHs)s 
H CoO CH3 
CHCH=C”% 
OC 0 CH” \coocH: 
N(CH): 
Thus the pyrethrins are esters of pyrethrolon with chrysanthemum 
monocarboxylic acid and ch yadnthiontiha dicarboxylic acid methyl 
ester. The toxic principles of pyrethrum consist of about 40 per 
cent of pyrethrin I and 60 per cent of pyrethrin IT. 
The foregoing formulas contain five asymmetric carbon atoms and 
are highly unsaturated. Owing to their extremely complicated 
nature, there is little or no hope for the technical synthesis of pyreth- 
rin I and II. 
Because of the possibility that less complicated compounds con- 
taining some essential grouping might have properties similar to 
those of the natural products, a large number- of esters in which 
pyrethrolon was combined with various acids and in which various 
alcohols were combined with the chrysanthemum acids were pre- 
ared. In a very few cases the resulting products were toxic, but 
in no case did the toxicity approach that of the natural pyrethrins. 
Even when an acid differmg from chrysanthemum acid by having 
one methyl group replaced by hydrogen was combined with pyrethro- 
lon, the product was only about one-eighth as toxic as the natural 
product and synthetic pyrethrin containing inactive chrysanthemum 
acid was very much less active. The reduction of one or more doubie 
bonds in either the acid or the alcoholic component completely 
destroyed the toxicity. Compounds of the chrysanthemum acids 
with bases were completely inactive. There seems therefore to be 
little prospect of obtaining commercial synthetic insecticides related 
to the pyrethrins. 
DISTRIBUTION OF THE ACTIVE PRINCIPLE IN CHRYSANTHEMUM 
CINERARIAFOLIUM 
It has long been known that the flowers of the Chrysanthemum 
cinerarixfolium possess insecticidal properties. The action of the 
stems is so slight that they are practically worthless as an insecticide. 
It has been generally supposed that the buds, or “closed”’ flowers, 
are more active than the mature or “open” flowers. The trade 
formerly divided insect flowers into three grades: “ Closed,” “half- 
closed,” (or “half-open”’),and “open.’”’ The “closed” flowers usually 
sold for about twice as much as the “open” flowers, which would 
imply that their insecticidal power is correspondingly greater. 
Gerard (93) is the only investigator who states in what part of 
the flower the active principle is chiefly found. According to him 
there are two active substances, an oleoresin and an essential oil, 
_ which are found principally around the ovaries of the flower, and to 
~ asmall extent in the corollas. 
