Date of Award

Spring 1970

Document Type



Chemistry & Physics

First Advisor

Arthur Westwell

Second Advisor

Allen Pope

Third Advisor

Richard Carr


Much controversy has arisen in the 1950’s and 196O’s over insecticides and their effect on soil, plants, and creatures of the earth. This controversy, brought to the attention of the general public by Rachel Carson’s Silent Spring, prompted an interest in this area as a topic for further experimentation. DDi was chosen as the specific object of Inauiry, since it is probably the best known and most widely used of the insecticides. The purpose was to find the effect, if any, of DDT on carbohydrate metabolic processes of rats. Specific enzymatic reactions in the Krebs cycle were selected for study. Heart and liver tissue were the sources for the enzyme. Both spectrophotometric and manometric techniques were employed for following these reactions, as these methods are rather standard for measurement of enzyme activity, insecticides are divided ?.nto two main classes: l) the organic phosphorus insecticides, such as malathion and parathion; and 2) the chlorinated hydrocarbons, such as chlordane and DDT, DDT (dichloro-diphenyl-trichloroethane) was first synthisized in 1874 by a German chemist. However, it was not until 1939 that its properties as an insecticide were discovered by Paul Miller, a Swiss scientist who subsequently won the Nobel Prize. DDT in powder form is not readily absorbed through the skin as it is when dissolved in oil solvents. It is insoluble in water, but readily soluble in organic solvents. Approximately 4% to 10% of the substance is soluble in petroleum solvents and 1.5% is soluble in 95% ethanol. Consequently, it is presumably stored in the organs rich in fatty substances, such as the adrenals, testes, thyroid, liver, and kidneys. DDT has three isomeric forms:

Specifications for the technical grade of DDT call for a setting point of 89° G. The p - p’ isomer is the primary toxicant implied byreference to DDT, There are conflicting theories concerning the mechanism of DDT: one put forth by Langer in 1944, one by Martin and Wain in the same year, and another by Campbell and West in 1945. Laugher states that the trichloromethyl (chloroform) part of the molecule confers upon DDT the lipid solubility postulated as a requirement to bring about penetration to the site of action. The p - chloroohenyl groups linked to the carbon is felt to constitute the toxic component of the molecule. Martin and Wain take the opposite view. The p - chlorophenyl groupings are felt to be responsible for the lipoid solubility and the trichloromethyl portion of the molecule furnishes the toxicity. In support of this theory, it is noted that toxicity is in direct proportion to the amount of HC1 liberated by dehydrogenation at vital centers of the organism.