Branched Chain Rule

The Rule of Branched Chains is a pattern according to which in homologous series of substances the strength of the narcotic effect is weakened as the chain of carbon atoms branches.

This rule was formulated at the end of the 19th century by the German chemist August Behold. He noticed that the narcotic effect decreases when the hydrogen atom in the drug molecule is replaced with a hydrocarbon radical.

For example, methane CH4 does not have a narcotic effect. Replacing the hydrogen atom with methyl CH3 results in the formation of chloromethane (chloroform) CH3Cl, which is already a weak drug. Further, when replacing another H atom with CH3, dichloromethane CH2Cl2 is obtained, which has an even stronger narcotic effect.

Thus, the rule shows that with increasing branching of the carbon chain, the narcotic properties of the substance decrease. This is explained by the fact that branched radicals prevent the interaction of the molecule with receptors. The Branched Chain Rule is widely used in pharmacology to predict the biological activity of substances.

The rule of branched chains is a pattern in chemistry discovered by the German organic chemist Hermann Staudinger in 1907 and studied in detail by him in his subsequent work. The position he formulated in 1899 was substantiated by references to the chemist’s personal experience and was supported by many references to theoretical reviews describing the development of the theory of organic compounds at that time. This rule allows us to predict an increase in volatility, boiling point, melting point and temperature range of existence for branched forms of organic molecules. In general, the rule is based on more general patterns and follows from earlier discoveries. The rule makes it possible to predict the preferred structures of organic substances for solving a number of problems. The historical significance of the rule is to describe the structure of substances that affect the body's sensitivity to drugs, and also affects the understanding of organic synthesis reactions.