Ethers - Like hydrocarbons, the longer the chain, the more potent the anesthetic . However, increasing chain length also increases toxicity and reduces induction time. Ethyl ether is seldom used, and divinyl ether is explosive and produces deep anesthesia too quickly. Halogenated hydrocarbons - Addition of a halogen can reduce or eliminate flammability, and can also increase potency . Compounds containing only bromine are generally not useful.
Compounds containing only chlorine are subject to limited use, are toxic, and can cause arrhythmias.
The best of the chlorinated agents are ethyl chloride and trichloroethylene, shown below. Fluorinated hydrocarbons are the most useful of the general anesthetics, and were first discovered as offshoots of the nuclear weapons program. The structures of a few representative fluorinated hydrocarbon general anesthetics are shown in the figure above. It is a poor muscle relaxant, and has some toxicity and propensity to cause catechol-induced arrhythmias. It also causes a slow induction period.