Trialkylboranes

Trialkylboranes are organoboron compounds with the formula BR3, where boron is bonded to three alkyl groups. The boron center is electron-deficient, giving BR3 species Lewis acidic character. Depending on the alkyl substituents, these compounds range from volatile liquids to waxy solids and are typically highly air- and moisture-sensitive.

Preparation methods commonly used in the laboratory include the reaction of boron trihalides (BCl3 or BBr3) with organolithium or Grignard reagents to yield trialkylboranes and inorganic salts. Another approach involves generation of BR3 by alkylation of boron reagents under carefully controlled conditions; in practice, these routes provide access to a variety of alkyl groups on boron.

In terms of chemistry and applications, trialkylboranes act as Lewis acids and serve as useful intermediates in organic synthesis. They are prominent in radical chemistry, most notably in certain polymerization processes where trialkylboranes or related boron reagents function as initiators. Triethylborane (Et3B) is a well-known example and is famous for its high reactivity toward air and its historical use as a radical initiator and, in combination with other compounds, as an ignition source in rocket engines. Other BR3 species vary in handling sensitivity and reactivity but share the general requirement for inert or strictly controlled environments.

Safety and handling are important: trialkylboranes are typically pyrophoric or highly reactive toward oxygen and moisture. They are stored under inert gas in dry solvents and require appropriate shielding and ventilation during use.